Class Object Modelling with Uml2.0

An Introduction to Class Modelling using UML (Unified Modelling Language)

Written by: Robin Beaumont e-mail: [email protected]

Date last updated: Friday, 29 May 2009 Version: 5 Health Informatics Class modelling with UML

How this document should be used: This document has been designed to be suitable for web based and face-to-face teaching. The text has been made to be as interactive as possible with exercises, Multiple Choice Questions (MCQs) and web based exercises. If you are using this document as part of a web-based course you are urged to use the online discussion board to discuss the issues raised in this document and share your solutions with other students.

Whom this document is aimed at: This document is aimed at three types of people:  Those who wish to become involved in systems development but are not interested in the nuts and bolts of programming. Such people are commonly called domain experts and act as bridges between a professional group (e.g. medics, Solicitors etc) to which they belong and IT experts.  Those just beginning professional computer science courses.  Those who wish to become involved in some form of analysis activity. This might be Process re-engineering or Data flow analysis etc.

I hope you enjoy working through this document. Robin Beaumont

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 2 of 53 Health Informatics Class modelling with UML Contents

You can see Youtube videos of the concepts discussed in this document at www.youtube.com/theoldorganplayer

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 3 of 53 Health Informatics Class modelling with UML a. Before you start This document assumes that you have the following knowledge and skills: Skills/ knowledge: You should be able to explain and provide examples of the following database concepts:  table,  record,  index,  foreign key,  relation, one to one, one to many, many to many If you are unsure of what these terms mean and are unable to provide examples, read through: http://www.robin-beaumont.co.uk/virtualclassroom/chap7/s2/dbcon1.pdf - provides details of what a table, record and index are. http://office.microsoft.com/en-us/access-help/database-design-basics-HA001224247.aspx - Microsofts Database design basics page, goes further than you need but provides a good section on relations and how they work.

Required Resources You need the following resources to work through this document:  The “Scenarios for practicing modelling techniques” handout available from http://www.robin-beaumont.co.uk/virtualclassroom/contents.htm and follow the links

 A UML case tool - Many of the concepts introduced in this document are difficult to grasp at first and are helped by experimenting with a Case Tool in addition to carrying out the exercises with pen and paper. Two such tools are Visual UML and MagicDraw. You can download a community version of MagicDraw at http://www.magicdraw.com/. In addition if you are reading this document as part of a course you are undertaking with the Royal college of Surgeons (Edin) or Edinburgh University you are registered as part of the academic programme for Magicdraw which means you are entitled to use the full personal edition of MagicDraw. To be able to use the full personal edition you need to contact your course administrator who has the codes to unlock MagicDraw.

You can see Youtube videos of the concepts discussed in this document at www.youtube.com/theoldorganplayer

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 4 of 53 Health Informatics Class modelling with UML b. Learning Outcomes -UML Classes/Instances This section aims to provide you with the following skills and information. After you have completed it you should come back to these points, ticking off those you feel happy with.

Learning outcome Tick box

Be able to describe the main characteristics of object oriented modelling 

Be able to provide brief details of the relationship between OMT and UML 

Be able to describe briefly the history of UML 

Be able to describe what an instance is, as used in object oriented (OO) modelling 

Be able to describe the three parts of a UML class 

Be able to describe the two parts of a class instance (often called an object) 

Be able to explain the difference between a UML class instance and a UML class 

Be able to describe misunderstanding between UML classes/instances and the 'is a type of' concept 

Be able to discuss the importance of context in identifying UML classes 

Be able to produce a list of candidate classes from a narrative description 

Be able to use Rumbaughs criteria to help refine an initial list candidate classes 

Be able to use Reingruber & Gregorys criteria to standardise class names 

Be aware of the use of workshops and informal class diagrams to develop UML class diagrams in a group  setting

Be able to identify and draw classes and instances using the UML notation 

Be able to explain the relationship between classes, attributes instances, tables, records and fields 

Be able to describe the varying amount of detail that can be displayed in a class diagram 

Be able to discuss the concept of “view” as it relates to class diagrams  c.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 5 of 53 Health Informatics Class modelling with UML d. Background In the past 30 years the profession of systems analyst (modeller) has come into being and developed rapidly. The first modelling techniques focused on designing databases, and for an enthralling description of the development of the first computer system, along with its database, for Lyons teashops in the 1950's See Georgina Ferry's excellent book, A computer call Leo. In the 1970's by Peter Chen who is very much still alive and continues to produce important research (http://www.csc.lsu.edu/~chen/chen.html) developed a diagrammatic description of certain aspects of the data requirements for a database. The diagram was called an Entity Relationship Diagram (ERD) and is still used today , you may have come across it when using Microsoft Access. The example below shows an example from a database to collect research data from those who suffer from diabetes and are also pregnant. It represents the data at a high level of abstraction meaning that it is not necessary to show details of the various fields or indexes, just the table names (i.e. entity types) and optionally the field names.

For more information about ERDs see: www.robin-beaumont.co.uk/virtualclassroom/chap11/s9/erds_1.pdf While ERDs are useful they are limited and a more modern approach is to use Class diagrams, this more modern approach is what we will concentrate on in the rest of this chapter.

Why learn about Class Diagrams? This chapter, along with and several subsequent ones, focus on getting you to learn what class diagrams are and how to produce them. You may ask why, so here are a few reasons I believe it is important for you to do so:  These diagrams form the basis of most database design methods. If you ever are involved in database design (i.e. data modelling) you will therefore need to understand them because if they are wrong (i.e. the blueprint), the database that is built from them will also be wrong!  These diagrams can be transformed to the more traditional ERD to create databases.  These diagrams provide a method of analysing a situation that forces you to adopt a stance of a typical database modeller. By using them you begin to realise how their minds work and also begin to appreciate why some databases are so problematic. These are only a few of the reasons that I personally believe this skill is so important. Even if you do not intend to become a programmer or systems analyst/modeller you may want to become the type of person who is able to provide a bridge between your professional group – such as doctor, vet or solicitor – and those who develop or manage information systems. Such people are vitally important in developing usable information systems and there is a great shortage of them. Such a person is often referred to as a ‘Domain Expert’ or subject matter expert (SME) Before you start to learn what class diagrams are and how to create them yourself there are some Multiple Choice Questions (MCQs) on the next page to see how much you have taken in so far.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 6 of 53 Health Informatics Class modelling with UML Exercise 1 MCQs 1. From the list below choose two reasons why it is important for a ‘domain expert’/subject matter expert (SME)such as you to learn about the Class diagramming method: a. Provides insight into the mindset of database developers b. Is the only method available to describe the data requirements c. Provides credibility to IT personnel d. Forms the basis of most data modelling techniques e. Has been proved to be the most cost effective method of specifying data requirements

2. From the list below choose the one option that describes the most desirable ‘domain expert’ from the medical profession: a. Someone who has developed several databases but knows little of database modelling or current issues in medicine b. Someone who has little interest in how information may help the department c. Someone who has problems working in a collaborative environment d. Someone who has previously managed IT projects e. Someone who has knowledge of data modelling techniques and currently works in the appropriate situation

1. ERDs provide a description of (one correct answer):

a. The processes that occur in the model b. The various entity types and their relationships in the model c. The entity types in the model d. The processes and data requirements of a model e. The User Interface aspects of the model

2. ERDs provide a (one correct answer):

a. A detailed description of the data within a data model b. A detailed description of the proposed uses of a database c. A guide to the training costs d. A high level description of the data within a data model e. A graphical picture that is of little use in developing a database e. Introduction The process of designing any system, whether it be computer, paper or person based or a mixture of all three, consists of specifying two important aspects, the what (data - structure) and the how (what it does - behaviour). Considering the How aspect, a system is worse than useless if it either is difficult to use (e.g. for entering or retrieving information) or hinders rather than facilitates working practices. For example, if a system is planned to be used in a medical consultation it should be easier rather than more difficult to prescribe and allow the users to collect data in the way they would find natural. While this How aspect is as important as the data side of things, we will concentrate on the 'what' side of things in this document. You may be familiar with ERDs, a graphical technique for specifying the what. However in this document we will be looking at a more advanced diagramming technique to produce diagrams explaining the What, namely UML Class diagrams. These diagrams are one aspect of ‘object oriented’ modelling techniques that have developed over the last few decades. Basically the Object oriented approach allows more complex models to be developed than previously possible. Before we consider the UML Class diagram in detail we will take a quick look at object oriented modelling techniques in general and UML.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 7 of 53 Health Informatics Class modelling with UML f. Object Oriented Approaches and UML In the early 1990s Rumbaugh as well as M Blaha et al developed a modelling process called OMT (Object Modelling Technique) which was documented in a book by them called Object-Oriented Modelling and Design, Prentice Hall 1991. This book has taken on the status of a classic and is still available although they have published what can be considered to be an update to this in 2005 – Object Oriented Modelling with UML . So what are Object Oriented Modelling techniques and how do they relate to this thing called UML? Object oriented modelling relies heavily upon the following five ideas (concepts), which allow us to model aspects of the world in a logically consistent manner. Notice this is much wider than just database modelling:  Classes and Objects  Association  Inheritance  Encapsulation  Polymorphism

In this chapter we will concentrate on the first aspect, although we will have a glance at the others in passing. So how does UML relate to Object Oriented Modelling? The answer is basically historical. In 1998, Rumbaugh joined forces with Grady Booch and Ivar Jacobson, who also have their own Object Oriented Modelling languages, to create a Unified Modelling Language (UML). That year saw a burst of activity with several books being published describing UML (Fowler & Scott 1998, Blaha & Premerlani 1998), UML not only subsuming Rumbaugh's OMT but also expanding it with new diagrams. Since this time UML has gone through a number of revisions with the most recent being version 2.4 (Around May 2011). I have therefore decided not to discuss OMT and the earlier versions of UML. The specification of the latest version of UML can be found at http://www.omg.org/. UML is definitely the "in thing" and if you look in any computing/ modelling/system development section of most large bookshops you will find a row of books about UML. Three that I would recommend are: Simon Bennett, John Skelton, Ken Lunn, 2005 UML: Schaum’s outlines. ISBN 0-07-710741-1 £10.99 [A much improved second edition – no cd but what can you expect at this price] Thomas A Pender: 2002 UML Weekend crash course. ISBN 0-7645-4910-3 [Also contains a CD with a pdf version of the book and a 15 day demo version of System Architect version 8.5 Costs about £15 – 20] You can get second hand copies of the above books for far less by looking on www.addall.com, www.Amazon.com and www.amazon.co.uk Only the Bennett books talks about uml2 in detail. UML provides a standard set of tools (most of us would call these diagrams – but the UML people get upset if you reduce them to such things!) for analysing and developing a model using an Object Oriented Approach. UML is not a method, you are free to use which tools (diagrams) you feel are appropriate and at the appropriate points you decide during the process. However this does not mean there is no relationship between the various diagrams; one of the most important aspects of a CASE TOOL is how it manages the relationships that exist between them as specified in the UML. Few if any modellers use all the diagrams; it depends upon the specific project and the personal preferences of the modeller. Fowler 2004, p.12 has a nice diagram showing the various diagrams in UML (version 2) taken from the formal UML specification document; the greyed out boxes represent the classification of the diagrams. In UML version 2 there was 13 different diagrams, and now in UML2.4 14 diagrams: In this and the following chapter we will focus on the Class diagram, probably the most important diagram in UML. But to help you understand what classes are we will look briefly at class instances (Objects) first.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 8 of 53 Health Informatics Class modelling with UML If you want a quick overview of UML and the various diagrams see: http://www3.software.ibm.com/ibmdl/pub/software/rational/web/whitepapers/2003/intro_rdn.pdf or http://www- 128.ibm.com/developerworks/rational/library/769.html Please note that both these sites by providing a very superficial overview make many technical errors - but they do provide a starting point. g. Class instances So what is a class instance in the context of 'object oriented modelling'? A class instance (often called an object in UML but I avoid this term) is best thought of as a definable thing with a number of facets that results in us perceiving it as something that is distinct. What are these facets? well in biology people often talk about something having form and function, we can think of the 'descriptive' side of things as being data (e.g. a person having a name, age, hair colour and address etc) and the 'function' side of things as being activities (e.g. washing hair, giving birth, going shopping etc). Moreover, the data (structure) and activities (behaviour) are inextricably linked in our conceptualisation of the instance. If the instance should change either its activities or characteristics it exhibits, we feel distinctly uneasy. In other words, when we conceptualise an instance in the world, we do not naturally divide it out into these two aspects. To do this requires skill. For example, when we see something we like, we tend to think of both actions as well as its characteristics (data), when one thinks of a banana or a bowl of soup, not only do both have pleasant characteristics such as colour and smell but they also have pleasant actions associated with them such as the soup being made (created, the default operation all instances possess) and eaten, and the banana growing and ripening, thinking of something more complex such as a Person, instances of this would be far more complex..

From the above we can say that we have two instances of class, Person and one each of class banana and soup. So we can have any number of instances for a particular class. In the context of 'instance modelling' a class instance is therefore something in the investigator's mind that usually possesses a recognisable number of both characteristics (data consisting of data items) and actions. As in all areas of computer science, one word is never enough; and UML uses the word 'attribute' instead of data or characteristic. The diagram above shows how class instances are drawn in UML. Each class instance is divided into two sections:  The top box gives the name of the class instance along with its class name (more about that below).  The bottom section lists each attribute along with its value, where each line is called a slot. All the above examples of class instances indicate that the attributes have values suggesting that the class instance exists in some way and because of this it often means class instances are called ‘ real world things’ but this can be misleading. If you know about ERD diagrams you may be thinking that the concept of a class instance is very similar to that of an Entity Instance. In fact you would not be far from wrong; however, the class instance concept also has the concept of Operations within it, they are just not shown in the instance diagram. In the above section we have discussed instances of Classes now we will investigate the actual Class concept.. h. Classes The best way to think of a class is to think of the blueprint idea. A class is often called a concept, although philosophers argue about the differences. Many theorists have provided complex definitions of a class or entity type, which is a similar idea, but none are complete or infallible. Hopefully by the end of this section you will be able to conceptualise what a class is in this context even if you still won't be able to provide a definition for it. Chen, one of the early writers (circa 1970), felt that the task of class identification (he was talking about 'entity types' at the time, as instance modelling had not been developed) was best left to the individual who was within, and who knew most about, the system to be modelled. This suggests that classes are partially dependent upon the person who is identifying them, and this will become clear as you work through this section. The domain expert / subject matter expert (SME) plays a vital function between the end user and IT/ programmers defining and correctly modelling classes.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 9 of 53 Health Informatics Class modelling with UML What then is a class? A class can be thought of as an abstraction from the instance. Notice that in the examples concerning instances a single banana was described. The instance 'mybanana' is said to be an instance of class banana. Similarly John is said to be an instance of class Person and “mysoup” an instance of class soup. Notice that while the class person could exist without any instances, the reverse is not true. We say that an 'instance' is an 'instantiation' of a class. This may appear rather pedantic but it is very useful in modelling as it provides a method of classifying groups of things often in very useful ways. Basically:  Class = Template  Instance = Example of a particular class

All instances of a particular class must have the same structure as the class

The rest of this section will be concerned with identifying and organising Classes.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 10 of 53 Health Informatics Class modelling with UML

Defined by context Below are some examples of classes and instances for three different contexts: A typical general practitioner planning on collecting information about patients:

Class Some possible instance(s):

Doctor Name=Angus Wallace. Residence= living in the UK

Patient Name=Joe Bloggs, Town=Newcastle , Name=Alan Smith, Town= London

Visit Time=12/06/2001/4pm location+Prospect House Newcastle

Prescription Drug=Valium, dosage=5mg. Frequency= eight times a day

Advice leaflet Title=Chronic back pain leaflet Title=UTI self management

The university administrator thinking about developing a course database:

Module Coordinator Name=Robin Beaumont, Name=Joe Brand

Student Name=Paul Whatling Name=Mary Brown Name=Anne Smith

Tutor Name=Ruth Brown

Module Title=Introduction to Informatics, year=2003

A garage collecting detailed information about car components:

Spark Plug Make=Rover, model=49532

Engine Escription=122 Brake Horsepower

Cooling system Capacity=17 pints

Gearbox Second gear ratio= 7.55:1

Propeller shaft Type=Hardy Spicer

Are the above examples correct? While the above examples probably list a selection of the important classes for each of the contexts, there is no absolute way of being able to say they are correct. Rumbaugh et al (1991, p21) makes this important point when discussing class identification: “We define a class as a concept, abstraction, or thing with crisp boundaries and meaning for the problem at hand. Classes serve two purposes: they promote understanding of the real world and provide a practical basis for computer implementation. Decomposition of a problem into classes depends on judgment and the nature of the problem. There is no one correct presentation.” [edited slightly] This is clear from considering the last example concerning car component details. Assume that another garage owner who was less concerned with collecting detailed information about each component only wanted one item of information recorded for each component. In this instance we would probably have CAR as the class and each of the

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 11 of 53 Health Informatics Class modelling with UML classes listed above relegated to attributes of the CAR class. There is no definitive correct answer; we only know by talking to the actual garage owner. Classes are largely defined by the context.

Presentation in UML Computer scientists, whenever possible, use diagrams or symbols rather than words. This is because words are considered to be the most ambiguous form of communication or more probably because most computer scientists are notoriously poor at English. The diagram below shows how UML would possibly represent several of the classes described previously: In the diagram each box represents a class. The box is divided into three sections. The top section of the box provides the name of the class, usually a noun. The next section down provides details of the data (attributes or data items) in the class while the last and final section provides names of the activities (methods) that make up the class. While the first two examples -- Person and Banana -- are relatively easy to define in this way, the third is more difficult. This is probably because Soup has a large number of attributes but has very few activities. The only one l could think of, besides the generic ‘create’ which all classes have, how else would you create instances? is the process of decomposing when it's left too long, possibly ‘heat up’ might be another. Not all classes have actions (other than the generic ‘create’ and 'destroy'), but all must have a name and something that uniquely distinguishes them from another class. Because instances are just instances of a particular class, these rules apply to them as well. In this chapter we will concentrate on class diagrams rather than instance diagrams; these being more general, they tend to be more useful. However, instance diagrams are useful if you want to investigate a particular situation.

If you know about ERD diagrams you may be thinking that classes and Instances (instances) are the same as Entity Types and Entity Instances however Classes and instances are far more complex because they possess operations as well as attributes.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 13 of 53 Health Informatics Class modelling with UML We will now take a specific example, assume that we have decided to propose that a valid class would be one named Doctor firstly we need to consider if this is a valid class, again context comes into play if we were creating a model for a general purpose employment agency we would probably have a more generic class such as client, with thewre profession as an attribute in the class, however if we were modelling a GP practice or hospital we would have Doctor as a specific class. Assuming we have the latter situation:

Another way of thinking about the bond between a class and instance is to think of the class as being the column headings (= attributes + operation names) for a number of rows each of which is an instance of the class. For example

Exercise 2 MCQs 1. Which one of the following is an example of a class: a. Robin Beaumont b. Carrot c. Date's book An Introduction to Database Systems on my shelf at home i. Spike from the TV series "Buffy the Vampire Slayer" d. My backup disk (in the second drawer of my desk)

2. Which one of the following is an example of an instance of a class: a. Course Manager j. Health Informatics courses k. Women l. Tony Blair m. Religion

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 14 of 53 Health Informatics Class modelling with UML This is how I arrived at the answers for the exercise on the previous page

1. Which one of the following is an example of a class: a. Robin Beaumont could be:

Class / instances. Possible Class name: person

First_name surname dob Mobile_1 email etc

robin beaumont 12/05/87 0798675664 [email protected] ...

Tony Milner 05/09/1967 0978675 [email protected] m

e. Carrot could be: Class / instances. Possible Class name: carrot

Variety Germination_date Seeding_position manufacture taste etc r

Old_red 04/09/2011 Plot4 thomsons Honey sweat ...

Tonys_specia 04/09/2011 Plot2 thomsons sharp l

f. Date's book An Introduction to Database Systems on my shelf at home Class / instances. Possible Class name: Book

name author publisher date etc

UML for beginners beaumont Brewester_brown 01/02/2016 ...

An intro to date wiley ?? databases

n. Spike from the TV series "Buffy the Vampire Slayer" Class / instances. Possible Class name: buffy character

name character First appearance Last appearance etc

James Marsters spike 1997 2003 ...

Seth Benjamin Gesshel-Green Seth Benjamin Gesshel-Green 1998 2001

g. My backup disk (in the second drawer of my desk)

Class / instances. Possible Class name: backup_disk

name size manufacturer date etc

Backup1 5.25 imac 02/09/2010 ...

My_backup_dis 3.25 dozik 10/09/2006 k

Backup3 5.25 imac 02/09/2010

Backup4 3.25 dozik 10/09/2006

So from the above only the carrot is at the class rather than instance level, the relevant entries are shaded yellow. A similar approach can be taken to the second exercise 2. Which one of the following is an example of an instance of a class: a. Course Manager - This is probably a class with a name attribute. o. Health Informatics courses - This is probably a class with attributes such as title, start_date etc p. Women - This is probably a class with attributes such as gender, surname dob etc q. Tony Blair - This is probably an instance of Human or Prime minister r. Religion - This is probably a class with attributes such as name, leader, estimated number of followers etc

While the table format is nothing to do with UML it does help to understand the link between the class and its zero or more instances

All instances of a particular class must have the same structure as the class

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 16 of 53 Health Informatics Class modelling with UML Exercise 3 Classes and Instances Spend five minutes filling in the tables below. List some possible classes along with examples of their instances. Some of your classes may have no or several instances. The important thing is that each instance possesses the same set of attributes as the entity type.

Exercise 4 UML Classes and Instances Part A Consider your job to be a class. If you do not have a paid job, you may be a student for example, then use that instead. List two of your (clinical) activities along with the information about them which you feel would be useful to collect. If it helps, consider it in the context of a learning log book of some sort. Part B Draw a diagram that represents the following classes: community nurse, GP, clinical manager in a hospital, day care coordinator, director of finance in an acute trust (hospital outside the UK), patient, yourself and your boss. Part C Draw an instance diagram that represents an instance of some of the classes you described in the above tasks.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 17 of 53 Health Informatics Class modelling with UML Exercise 5 MCQs 1. Which of the following provides the best description of a Class (select one)? a. A specific concrete object with a defined set of processes (e.g. John Brown with diabetes) b. A value given to a particular attribute (e.g. height - 230 cm) c. A thing that we wish to collect data about where one or more, real world examples of it exist d. A template for a group of things with the same set of characteristics that may exist in the real world e. An undefined concept that needs further clarification

2. Which of the following provides the best description of a class instance (select one)? a. A specific concrete object with a defined set of processes (e.g. John Brown with diabetes) b. A value given to a particular attribute (e.g. height - 230 cm) c. A thing that we wish to collect data about where one or more, real world examples of it exist d. A template for a group of things with the same set of characteristics that may exist in the real world e. An undefined concept that needs further clarification

3. From the following list, select two class instances: a. Steinway piano model D design template b. McGill type forceps as used in surgical operations c. Tony Blair ( British prime minister) d. PIII type chip that is found in many modern PCs e. An advice leaflet for chronic back pain issued to Mrs Smith on 02/10/2002

4. Which one of the following statements is true (select one)? a. A UML class diagram can only display class names. b. Attributes are a rarely considered aspect of classes. c. Attributes must always be displayed in UML class diagrams. d. Attributes equate to table names in a database. e. Attributes can optionally be displayed in UML class diagrams.

5. Select from the following the best list of attributes for the class SHOE for someone working in a shoe shop (select one answer): a. 1, 2, 6 b. 1, 2, 6, 3 c. 1, 2 d. 1, 6 e. 1, 2, 3, 4, 5, 6

6. Select from the following the best list of attributes for the class RECIPE for someone following a recipe at home (select one): a. 4, 5, 7, 8 b. 4, 5 c. 4, 5, 6 d. 4, 5, 8 e. 4, 5, 6, 8

Identifying Classes While there is much written concerning UML and Class diagramming theory, far less has been written about actually developing the models. Two of the most common ways of identifying classes for developing UML class diagrams are:  Narrative descriptions of requirements  Workshops Both of the above methods rely to some extent on expert domain knowledge to identify and classify classes. We will now look at the first method, using a narrative description of the system requirements on which to base the development of a UML class diagram. Rather than give a brief description of each stage and then visit each in turn, I will just take you on a journey and then reflect upon what we will have done in a summary at the end. So now let’s start with the narrative description.

Analyzing a Narrative Description to identify candidate classes Frequently the first thing to be produced when someone has the idea of developing a model (also called "the system" or "database" below) is a paper document describing what he or she wants. This often includes something like the following: We wish to develop an information system for our hospital in which: “Patients are treated in a single ward by the doctors assigned to them. Usually each patient will be assigned a single doctor, but in rare cases they will have two. Patients either pay for their treatment directly or through an insurance company. Healthcare assistants also attend to the patients, and a number of these are associated with each ward. Initially the system will be concerned solely with drug treatment. Each patient is required to take a variety of drugs a certain number of times per day and for varying lengths of time. The system must record details concerning patient treatment and staff payment. Some staff are paid part time, and doctors and care assistants work varying amounts of overtime at varying rates (subject to grade). The system will also need to track what treatments are required for which patients and when, and it should be capable of calculating the cost of treatment per week for each patient. When users use the system they will be able to print out as well as view on screen the results. (Although it is currently unclear to what use this information will be put.) “ (taken from http://www.umsl.edu/~sauter/analysis/er/er_intro.html and expanded)

The first stage is to pick out all the nouns (names) in the above passage; this provides a good baseline from which to consider possible entity types.

Exercise 6 Marking Nouns

Mark in the above narrative all the nouns (names) you see.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 19 of 53 Health Informatics Class modelling with UML You can see in bold below the possible set of nouns (names) that I have come up with: “Patients are treated in a single ward by the doctors assigned to them. Usually each patient will be assigned a single doctor, but in rare cases they will have two. Patients either pay for their treatment directly or through an insurance company. Healthcare assistants also attend to the patients, a number of these are associated with each ward. Initially the system will be concerned solely with drug treatment. Each patient is required to take a variety of drugs a certain number of times per day and for varying lengths of time. The system must record details concerning patient treatment and staff payment. Some staff are paid part time and doctors and care assistants work varying amounts of overtime at varying rates (subject to grade). The system will also need to track what treatments are required for which patients and when and it should be capable of calculating the cost of treatment per week for each patient. When the users use the system they will be able to print out as well as view on screen the results. (Although it is currently unclear to what use this information will be put.)” (taken from http://www.umsl.edu/~sauter/analysis/er/er_intro.html and expanded)

Gathering together all the above nouns produces the following list, not in any specific order:

Candidate classes Patients System Doctors Users Healthcare assistants Cost Care assistants Time Ward Day Drug treatment Lengths Drugs Details Patient treatment Overtime Treatment Rates Staff payment Grade Staff Week Insurance company Results Screen Use Information

Each of the above nouns can be considered to be a 'candidate class'. The next stage is to consider which of these are appropriate classes to include in the UML class diagram. To do this we consider Rumbaugh et al (1991 p152-3, repeated in Blaha & Rumbaugh 2005 p 185 -6) criteria.

Developing candidate Classes Rumbaugh et al (1991 p152-3, repeated in Blaha & Rumbaugh 2005 p 185 -6) provides some guidance as to how to identify appropriate classes. He suggests that you consider the following issues:  Redundant class types Two class types may express the same information (i.e. two names for the same concept, or synonyms). In the above example DOCTORS and HEALTHCARE ASSISTANTS (HCA) might be considered to be just class instances of the class called STAFF; however, this is unlikely in the above example because we know from our own expert domain knowledge that doctors are concerned with prescribing whereas healthcare assistants are not, they therefore have different activities, furthermore some of the attributes will be different, doctors possess a GMC number whereas HCA's do not. In addition the information we plan to collect is specifically concerned with prescribing. We therefore consider the class type STAFF to be redundant, at least for the time being; possibly when the system is developed further such considerations can be re-visited.  Irrelevant class types If an class type has little or nothing to do with the problem, it should possibly be left out. In the above example one would need to clarify with the person requesting the system if they need information stored about INSURANCE COMPANIES. Also if the system is initially only concerned with drug treatments, is there any point collecting information about other treatments?  Vague class types In a narrative description, often words are used indiscriminately. In the above example the description states that “Initially the system will be concerned solely with drug treatment” yet the following paragraphs refer to PATIENT TREATMENT and also TREATMENT. Are these three different class types or not? Again we can only find out by discussing this issue with the person who requested the database. We would probably suggest that we have two class types called DRUG TREATMENT and TREATMENT where TREATMENT is concerned with information about any non-drug intervention and probably not included in the initial ERD.  Class types that are really attributes Often an initial class type is an attribute. In the above, COST has been classified as a possible class yet it is probably an attribute of TREATMENT or DRUG TREATMENT or PATIENT (renaming it BILL).  Multiple roles become class types "The name of a class type should reflect its intrinsic nature and not a role that it plays. For example, OWNER would be a poor name for a class type in a car manufacturer's database. What if a list of drivers is added latter? What about persons who lease cars? The proper class is PERSON (or possibly CUSTOMER), which assumes various different roles, such as owner, driver, lessee." (Blaha & Rumbaugh 2005 p 186). Similarly a doctor is not just a prescriber but a treatment giver and a reviewer of results.  Implementation information The Class diagram is concerned with defining the data that needs to be stored. It is not concerned with the hardware or processing of the data. Therefore, in the above example SYSTEM, SCREEN and USER can be ignored. Similarly RESULTS are an outcome of processing data. Perhaps from your knowledge of Access or other databases, you will realise that such things as RESULTS and reports are just a process of using a query or report tool to interrogate the model. Another type of problem occurs resulting from the existence of homonyms. This is where two classes with the same name actually mean different things. For example the class TREATMENT may mean very different things to different healthcare professionals. In this instance it may be necessary to add one or more additional class types to express the different concepts more clearly (e.g. DRUG_TREATMENT, DIETARY_PRESCRIPTION and ART_THERAPY etc). So what have we ended up with after all the above deliberations? The following is the revised list of class, for as very simple first list which will obviously expand: Patients, Doctors, Drug treatment, Drugs

By concentrating on the drug aspect of treatment and considering each of Rumbaugh’s guidelines we have reduced the list from 27 to 4 for a possible initial UML class diagram.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 21 of 53 Health Informatics Class modelling with UML Exercise 7 Identifying Classes from a Narrative Time: 60 minutes Look through the DopeHead scenario, found in the scenarios handout, and: 1. Mark all the nouns and produce a list of them. 2. Using Rumbaugh’s guidelines revise your list to identify candidate classes.

Applying naming standards to Classes While the previous page was concerned with identifying classes, we will now look at one of the many informal naming standards suggested, this one is by Reingruber & Gregory 1994 (p65-77). Class names: Should be unique for the particular model. (This does not usually apply to attribute names which only need to be unique to a particular class) Should be a singular noun (e.g. PATIENT not PATIENTS). Should be self-explanatory to those reading the UML class diagram. Should follow any naming conventions locally defined by the modellers. For example, two common constraints are that: . They should be written in UPPER CASE. . Possible spaces should be represented by the _ character (eg DRUG_TREATMENT rather than DRUG TREATMENT). Should not be a name of an individual instance (e.g. Freeman Hospital Newcastle upon Tyne). Should not express more than one concept (e.g. EQUIPMENT/BED). Should be documented in addition to the diagram The description for each class should be clear, unambiguous and supplemented with examples of instances.

When carrying out this process it is a good idea to draw up a table similar to the one below to make sure you carry out the process, the initial proposed class type name on the left and the final class type name on the right.

Initial class Unique Singular Self- UPPER The _ Not a Not more than Documented Final class type name: noun explanatory CASE character individual one concept type name object

Patients

Doctors

Drug treatment

Exercise 8 Applying standards to Classes Time: 60 minutes 1. Looking back at the hospital example, consider the following four possible classes. Use the above guidelines to edit them appropriately:  Patients  Doctors  Drug treatment  Drugs 2. Revisit the initial set of classes you defined for the DopeHead scenario and edit them accordingly. It may help to draw up a table similar to the one above.

Workshops The alternative to using a paper document to partially derive a set of classes is to hold a series of interactive workshops. This requires commitment, including the willingness to learn, from the person(s) who have requested the system (i.e. database). They need to understand to a limited extent what you are learning now! Often a mixed approach can be taken, using a paper document as the starting point, to a workshop. Running workshops requires good group working skills, and must be carried out in a non-threatening manner. Often the modellers need to show considerable tact when people get hung up on what the modellers themselves know to be irrelevant issues (e.g. font size/colour, type of screen or computer etc) for the particular task at hand. Now that we have looked at how to create an initial list of classes we will consider the actual mechanics of drawing UML class diagrams

Drawing UML class diagrams - Case tools It must be remembered that systems modelling, of which UML is one particular aspect, is a discipline that has only been in existence for about a quarter of a century. I was recently looking at a book on systems analysis written in 1984 (Daniels & Yeates) and only 2 of the 300 pages was dedicated to a similar topic of databases, and within those two pages no mention was made of diagramming. To begin with learning to draw UML class diagrams is usually a pen and paper exercise and I would strongly encourage you to practice using this simple technique at the start - be warned you'll also need a large rubber! Drawing informal UML class diagrams and discussing them is a very good way of developing them in a measured and appropriate manner, flip charts, or electronic white boards are excellent in this respect. Other documents on my web site provide detailed tutorials on how to use specialised software (called case tools) to draw UML class diagrams. http://www.robin-beaumont.co.uk/virtualclassroom/contents.htm

Class Diagrams and Amount of Detail Shown In a uml class diagram, varying degrees of detail of a class can be shown. Sometimes all that is shown is the class name. Alternatively the class name and attributes are shown, or alternatively both the attributes and operations are shown.

Views At the beginning of this document it was stated that the identification and description of Classes/instances was partly a matter of individual interpretation. This is clear when one considers the examples given above. Now considering the NHS, a patient as perceived by a hospital chaplain is a very different instance from that perceived by a director of finance. If you asked each to draw a Class diagram like those given on the previous pages, each would come up with a different set of data and activities.  A model is always context specific.  It is never purely a reflection of reality - whatever that is! It is interesting to note that a large amount of effort in the modelling process is directed towards getting these differing views consolidated in some way. The potential problem is tackled in different ways depending upon the particular software development lifecycle chosen. Frequently a stakeholder or cultural/political analysis is carried out to see how important each of the views are, thus allowing a way to prioritise one view over another. Another method is used during the actual software development phase of the lifecycle where different views, or user interfaces, to the data can be developed for different user types. These are just two of a whole host of techniques available to tackle this problem. This concept of a view is similar to that of a 'semantic purpose’, which is described on page 22 of Rumbaugh (both editions same page). The importance of being aware of potential problems with differing views in the healthcare sector is discussed in: Willcocks P L. Mark A L. (1989) IT systems implementation: Research findings from the [health care] public sector. J I T [June] 92 – 103

Exercise 9 MCQs

1. Which of the following types of software (applications) is most suitable for developing UML class diagrams?

a. Desktop drawing package (e.g. Smartdraw) b. Desktop publishing application to ease the use of textual explanations c. Anything with drawing capabilities (e.g. Microsoft Word) d. A CASE tool e. A spreadsheet

Exercise 10 Different viewpoints Describe what might be the main differences in viewpoints between some of the following:

 community nurse  GP  clinical manager in a hospital  anaesthetist  day care coordinator  paediatrician  psychiatrist  microbiologist  director of finance in an acute trust  patient

You may want to devise some type of table to help you organise your thoughts.

Warning about the ‘is a Kind of’ Situation To start with, people are often confused about the connection between classes and instances thinking that an instance “is a kind of” class. An example will help to make this clearer. Someone might say that for the class ANIMAL instances in this case might be BIRD or HUMAN. This is not usually the case. The reason for this is because thinking about the structure, that is what attributes and behaviour you might want to collect about BIRDs and HUMANs would probably be different in several respects for each of them. Would you really want to collect information about the size of wingspan for a HUMAN or the IQ of a particular bird? In other words the set of attributes and operations for each is different. Unfortunately it is not always as simple as this. Here is the argument for keeping BIRD and HUMAN as instances of HUMAN. Suppose you were an antique dealer and just wished to collect information about the instances of ANIMAL statue you had. In this case you would probably just want to record the number of ANIMAL statues you had rather than be animal specific, information in which the amount and type would vary for each. In this situation you are happy about keeping the same type of information about each of the statues regardless of what they represent, probably just species name would do for your attribute name. The context dictates what class types you will find.

Class = ???

First_nam Bra size Dress size Inside leg Date of birth Waist size e

Mary aa 2 01/02/45 60

John 90 23/12/67 89

Dave 86 10/10/68 103

Philip 110 14/08/98 98

Anne d 14 26/04/78 70 Lest consider another example. This time assume we have a class called ??? with the following 5 instances with some of the attributes shown. You will notice that you can divide up the instances into two groups based upon the empty attributes. It look like we need actually two classes here one for men and one for women? However we do have a certain level of commonality between them with the First_name, Date_of_birth and waist_size attributes. We will learn latter that this 'is a kind of' situation bed be very effectively modelled by using a concept called inheritance in UML class diagrams. Much more about this latter.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 24 of 53 Health Informatics Class modelling with UML For now the take home message is each class in a UML diagram: Has a DIFFERENT STRUCTURE (i.e. Different attributes and methods)

Tight coupling From the above sections you will realise that each class has a distinct set of attributes and operations, not only it is vitally important that each class is distinct from others in the model but the class must be a closely knit structure for example a patient class should not have leakage from other classes in the model such as GP or APPOINTMENT in the model below.

Exercise 11 Inappropriate attributes Consider the following classes and mark the attributes you feel are inappropriate in each class. Remember that the attributes in a class are those that define the class not aspects that may relate to it.

Class diagrams and Databases UML is often used, BUT NOT ALWAYS to develop computer systems and frequently these are databases. When people first start developing databases they always make two fundamental errors. Firstly, they rush to a computer to play with the DBMS (e.g. Access). Secondly, they believe they can create a perfect database by specifying a model without creating a prototype of some sort. It is vitally important to get the design right, but this involves many revisions resulting partly from feedback from people using the actual database. For each iteration the Class diagram(s) allow you to create a blueprint (model, specify, design, etc) of the data, and the DBMS allows you to create (implement, develop, etc) the actual database. In the diagram to the left, the data dictionary is shown as a half-way house between the 'high level' class model(s) and the actual database. Depending upon your inclination it is often not necessary to produce a data dictionary as a detailed description of each instance is adequate; it is basically up to you and whomever you may be working with. (See Blaha & Premerlani 1998 for more detail.) Again I must reiterate Class diagrams are not only used to develop databases!

The Relationship between Classes/Instances to Databases If we accept the object oriented view of the world, databases themselves are also simply a collection of classes/instances. More specifically a table is simply a way of allowing the computer, via a piece of software called a DBMS (Database Management System, e.g. Access), to store these classes/instances. This all sounds rather abstract, so I will now provide a example. The diagram opposite demonstrates the relationship between the class Patient and a DBMS table structure. The attributes in the class diagram become fields in a table where the table name is the same as the class name. Taking this one step further, a class instance is equivalent to a record in a table in the database.

Exercise 12 Linking Classes and Instances to Databases Spend a few minutes taking some of the classes / instances you have identified in the previous exercises and draw a similar diagram to the appropriate one above.

Specifying data types Fields in databases besides having a name also specify what type of data they store, for example it might be a number of characters (called a string), a whole number (called an integer) or a true/false value (called a Boolean) similarly in a uml class diagram you can specify the data type of individual attributes providing an even greater degree of linkage between the UML class diagram and a database structure.

Derived Attributes and Default values Often in databases field (attribute) values are derived from other field (attribute) values and you can show this in UML classes by using the forward slash(/) before the name, for example say we have a derived attribute in the Patient class called bmi (Body Mass Index) which is derived from two other attributes in the class height and weight, the situation opposite. Optionally you can add a note to the UML class diagram to provide additional details, but I personally prefer to add the detail to the narrative accompanying the diagram as the diagram gets very cluttered with lots of notes. The derived attribute does not necessarily use attributes from within the class but can make use of attributes from others. When a new record (instance) is created the actual value for each of the attributes is empty, however it is often useful to set a default value for some of the attributes. In the example below we have two more attributes in the patient class called dateRegistered data type date, and isHypertensive with datatype Boolean, for the former attribute the default value is the date their instance was created i.e. today and for the latter attribute it is given the value, False indicating that they are not hypertensive.

Operations So far we have not discussed the third section in each class in UML class diagrams which specifies the behaviour of the class, its dynamic aspects. Although clearly this aspect is very important, discussion of it will be deferred to the chapters concerned with dynamic modelling.

Summary - identification and development of classes In this section we have specifically gone through various stages to come up with a list of initial classes for both the hospital and Dopehead scenarios and we have also considered how the class attributes relate to database structures and the common misunderstanding that instances are considered to be a 'type' of class. Obviously we can also use this class identification method to produce a list of classes from any narrative description and the list below provides a resume: 1. Identifying nouns and drawing up a list 2. Removing: a. Redundant classes (e.g. synonyms) b. Irrelevant classes c. Vague classes d. Classes that are really attributes e. Multiple Roles amalgamated into a single class f. Implementation information 3. Adding classes due to homonyms 4. Considering Reingruber & Gregory 1994’s guidelines creating a table with the following columns: a. Initial class type name b. Unique c. Singular noun d. Self-explanatory e. UPPER CASE f. The _ character g. Not an individual object h. Not more than one concept i. Documented j. Final class type name

Exercise 13 MCQs 1. Which one of the following best describes the technique used to identify classes in a narrative?

a. Identification of verbs, the application of various criteria and standards (eg naming conventions etc) to refine the list and then the creation of a list of appropriately named classes b. Identification of nouns then the application of ISO standards to create a list of appropriately named classes c. Identification of verbs then the application of standards (eg naming conventions etc) to create a list of appropriately named classes d. Identification of nouns, the application of various criteria (e.g. Reingruber & Gregory 1994’s) and standards (e.g. naming conventions etc) to refine the list and then the creation of a list of appropriately named classes e. Identification of a few important nouns then the application of standards (e.g. naming conventions etc) to create a list of appropriately named classes

2. Which of the following criteria are true (choose three)?

a. Attribute names must always be unique for a particular model. b. Class names must be unique for a particular model. c. Attribute names must be unique for a particular class within a model. d. A class should only express one concept. e. Class names should be either singular or plural nouns.

Space for you to make additional notes about Classes and Instances:

Part Two

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 29 of 53 Health Informatics Class modelling with UML s. Linking Classes So far we have considered classes as being distinct discrete concepts with no linkage between them, however in reality classes obviously link to one another in many different ways and UML provides methods for modelling this. t. Learning Outcomes This chapter aims to provide you with the following skills and knowledge. After you have completed it you should come back to these points, ticking off those with which you feel happy. Learning outcome Tick box

Be able to identify and draw the different types of associations between classes including end names 

Be able to describe the concepts of aggregation and composition 

Be able to describe the way association lines in class/object models are implemented in a database 

Be able to describe briefly the concept of semantic modelling 

Be able to describe, and provide an example of inheritance 

Be able to describe the various ways of modelling inheritance 

Be able to demonstrate the usefulness of inheritance when modelling healthcare concepts 

Be able to describe the concept of polymorphism 

Be able to develop a class model for a familiar area 

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 30 of 53 Health Informatics Class modelling with UML u. UML Associations When modelling a system, in terms of classes it is vital to be able to model the way in which classes relate to each other. This is achieved by considering associations between classes. Although association modelling can be at a number of levels of complexity, we will only consider some of the simpler techniques available. An association often appears as a verb in a sentence, such as: A person [class] eats bananas [class] or Sally [instance] eats the banana [instance] on her desk

The verb is often helpful to aid understanding of the association and is frequently used to provide a name for the association. If this is the case it is placed somewhere beside the association line on the diagram. At a further level of complexity, a 'role name' can be placed at either or both ends of the association. A role name is simply taking the class and refining it in a particular way. For example: Person [class] works for NHS [class]. The association line at the 'Person' end could have 'employee' as the role name, with 'employer' as the role name at the NHS end. An association at the instance level is called a link. Once again UML has a sets of symbols to describe what are considered to be the common types of associations that exist between classes I have listed most of them opposite for easy reference: The multiplicity indicator, that is the 1, or 0..* or * etc. refers to the class close to it (i.e. proximal for the medics among you) on the line

All of the associations in the diagram opposite provide information about how many instances of one class can be associated with ('related to') another. Because these associations are concerned with the number of occurrences, they are often classified by their 'multiplicity' and on the next page examples are given of each type of multiplicity. It should be noted that working out the type of relationship that exists between classes is often done after it is agreed that some type of relationship exists. Therefore a first draft of a class diagram may possess many unmarked ('unspecified') associations which are only subsequently elucidated. We will begin by looking at the first four associations.

Multiplicity Multiplicity specifies how many instances of one class relate to a single instance of an associated class. The simplest type of multiplicity is that of one-to-one. This is shown as the first example below. Two classes that have a one-to-one association will therefore be drawn with a simple line between them with '1' at each end.. Such an example might be a needle and syringe or a person and coffin. Considering a slightly more complex situation, a frying pan may optionally have a lid, which would be represented by using the "0..1" multiplicity expression. You will also notice here that I have multiplicities at both ends of the association line.

If the modeller wishes to explicitly state how many occurrences of one class are associated with another, a value can be placed at the relevant end of the association line. For example, if a team leader always has four or more case workers this situation would be represented with '4+' above the association line. Discrete values can also be modelled such as in the situation where a team leader can only have 3, 5 or 6 case workers; this situation would be represented by '3,5,6' above the association line in versions of UML before version 2 there seems to be no mention of the use of such discontinuous sets which have again disappeared in version 2.4. Multiplicity is directional; the end of the line where the symbol occurs relates to the class at that particular end of the line. All the symbols mentioned above can occur at either end of the association. A few examples are given above using the UML notation. If you know about ERD's and the crows feet notation you will have realised that the above types of associations are basically the same as those. However UML provides a much greater variety of association types not found in ERDs and we will now move onto one of these, that is the diamond shape which we will discuss next.

Exercise 14 Associations

Draw some associations between the classes you defined in the earlier tasks.

Aggregation and Composition  These are special types of relationship. Let’s consider aggregation first. Aggregation can be translated into words as meaning consists of. In the last example in the diagram on the previous page, a person consisted of organs. In technical speech we would say that the person was the 'assembly' class and the organ was the 'component' class. The assembly class can be thought of as a type of collection. Taking another example, the MSc/DMI courses consist of a collection of units/modules. It is important to realise that the assembly class may have additional properties that the sum of the component classes may not have. For example, considering the organ and body example each individual organ has a name but the body adds additional details when they are all combined such as occupation. An assembly class ('collection') can be made up of more than one type of component. For example, a hospital consists of collections of hopefully both patients and staff. Fowler, 2004 p.67 considered aggregation to be a problem because different people interpret it differently; he quotes Jim Rumbaugh in saying “think of it as a modelling placebo”. I thought that the medics among you would appreciate that! Composition is more clearly defined as it includes the constraint of co-existence of the part as part of the whole, quoting from the UML standard: “A form of aggregation which requires that a part instance be included in at most one composite at a time, and that the composite instance is responsible for the creation and destruction of the parts. Composition may be recursive. Synonym: composite aggregation.” UML 2.0 Infrastructure Specification, Terms and definitions section.

In other words in composition the assembly class is in charge of destroying the component class and this implies that both parts have a degree of co-existent life cycles; the part can not exist without the ‘whole’. Thinking about the above definitions of Aggregation and Composition you can see why it is often difficult to decide which to use. For example, take the situation of the PERSON has ORGANS, shown on the previous page. To a priest this is a clear example of Composition; an ORGAN can only exist as part of a PERSON. To an organ transplant co-ordinator, however, it is very much an aggregation; organs certainly do exist on their own! Again, this demonstrates how models are context specific. Graphically the difference between aggregation and composition is that aggregation is an open diamond while the other is filled.

Exercise 15 Aggregation and Composition

Draw class diagrams showing the data for each of the following aggregations / compositions: bed, ward and hospital, canteen department and a department of your own choice.

Ternary associations So far I have only mentioned associations which involve two classes, however you can have associations which have more than two classes involved called n-ary associations, specifically one involving three classes is called a Ternary association. Let's consider an example, below is shown a ternary association between Lecturer, Book and Module. What does this mean? Well it indicates that there is a clear association between a specific lecturer, book and module. For example with this diagram we could be able to discover that Lecturer Joan uses the book 'UML and spirituality' on the module 'modern theology'. In other words we are defining a set of three specific values lecturer book (L,B,M) in contrast to two specific values for an association involving two classes.

module

The first three non uml diagrams above indicate instances between Robin, Joan and Andrew who are three instances of Lecturer and other instances in the ternary association, the last one attempts to put them all together. Given this complexity you may feel inclined to simplify the situation and model it with two or even three binary associations. Is this possible?

Breaking Ternary associations into Binary ones Most books recommend that it is sensible to convert ternary associations into a series of binary ones after one has considered the semantics of the particular situation you are modelling. For example we might assume after discussions with a group of lecturers that they ALWAYS

lecturer book recommend one or more books for a module. If this is the case then you could re-model the situation as shown on the left. But this means that any new lecturer instance that came along would need to play by the same rules. Is

module this reasonable? Also more worryingly by following through the new associations from Book to module, we do not really know which module which lecturer teaches on. Take for example, lecturer instance robin who is associated with book instance ABC of UML, however the book instance ABC of UML is associated with module instances Modern theology, Salesmanship and Home improvements, we might mistakenly now assume Robin teaches these, very different from the ternary relationship!

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 34 of 53 Health Informatics Class modelling with UML Can we mimic the Ternary association by adding another binary relationship between Module and Lecturer? In the above example by considering the association between Lecturer and book and Book to Module (the green lines) we have four possible instances. In addition considering the association between Lectuer and module we have another four possible instances, How ever by considering the situation where both associations overlap (the shaded row in the Book, module instances) there is a unique association. So in this example we can identify the specific Book instance Lecturer Robin uses in the Modern theology module. But is this always the case? Taking another example, that of a instance of Lecturer, Joan lets see if we can identify a unique instance of book she uses for a particular instance of module, put simply can we identify which book(s) she uses for a particular module. From the diagram below it looks that this time we can't because there are two possible instances of the book ABC of UML associated with the Salesmanship module. In fact looking back at the ternary associations diagram we can tell from that, that the other instance is associated with lecturer instance Andrew. But it is impossible to derive this information from the binary associations we have set up below.

In conclusion it is possible to say that: While ternary associations can be occasionally broken down into a series of binary associations the resulting semantics are subtly different to those of the original ternary association. It is the responsibility of the modeller to ensure that the semantics of the final model truly reflect what the client is attempting to describe. On the right are four examples of possible ternary associations, but remember that in particular circumstances they might be broken down to binary associations.

Recursive associations Recursive relationships are also called unary or involuted relationships. So far we have discussed examples of relationships between classes; however, it is possible to an association within a class. Such a relationship is called recursive. The usual example given is that of an EMPLOYEE class type that has a relationship with itself called supervisor. In other words an EMPLOYEE instance can relate to another EMPLOYEE instance in a supervisor role.

Clearly a ‘one to many’ or ‘many to many’ recursive relationship may also exist. (see Carter 1995 p61 - 68, Elmasri & Navathe 1989 p. 49) Some writers suggest that these recursive relationships are acceptable in early models but should be converted to ‘one to many’ or ‘one to one’ relationships, as the model is refined. For example the above recursive relationship could be modelled by introducing a new class type called ROLE. This was discussed in the ERD document.

Association End Names In UML the concept of Association end names s used to specify a role a particular instance may play in the association. Considering the above example an Employee may only have one supervisor and the supervisor will manage one or more employees. Association end names may also be used to clarify the situation where several associations exist between a single class. For example consider the situation where a courier makes journeys which require both a start address and a destination address, this can easily be modelled using association end names as shown in the diagram below (adapted from p. 97 Bennett, Skelton & Lunn 2005).

In contrast to the suggestion above concerning the use of 'Role' classes Blaha & Rumbaugh 2005 p. 32 suggests that recursive associations should be retained using association end names and provides the following example.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 36 of 53 Health Informatics Class modelling with UML Exercise 16 MCQs

The following questions relate to the class diagram below, concerning farmers, farming locations and lambs.

1. In the above diagram, which is the correct statement? a. A farmer has one or more lambs. v. A farmer has one lamb. w. A farmer has zero or more lambs. x. A lamb does not necessarily have a farmer associated with it. y. It is impossible to ascertain the relationship between farmers and lambs in the above diagram.

2. In the above diagram, which is the incorrect statement? a. A farmer has one or more farming locations. z. A farming location is associated with zero or more lambs. aa. A lamb is always associated with one farmer. ab. A lamb can be associated with more than one farming location. ac. A lamb consists of body parts.

3. The above diagram uses: a. OMT notation ad. UML notation ae. ERD notation af. No formal notation ag. Chen notation

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 37 of 53 Health Informatics Class modelling with UML ah. Mapping Associations to Databases The instance modelling concept of association is pretty much the same as the database concept of a relationship. I will not bore you with the technical details of relational databases, which are based upon mathematical set theory. If you are interested you can consult the standard book on the subject - Date C J. 1995 (6th ed.) An Introduction to Database Systems. The relational database model was first described by Codd in 1970 who subsequently defined a set of rules based upon mathematical principles. His papers are referenced in Date 1995. However what I will provide in the next sections are examples of the relationship between associations in instance models and relationships in relational DBMSs.

One to Many Relationship Consider the relationship between a doctor and patient. One doctor may have many patients. (Forget the situation of a patient having more than one doctor for the moment.) This can easily be drawn using UML: But how do we turn this into something that can be represented as one or more tables (i.e. something that can be used by a computer)? The answer is that we make use of foreign keys. If you do not understand the concept of relationships and foreign keys see: http://www.robin- beaumont.co.uk/virtualclassroom/chap7/s3/dbcon2.pdf A foreign key is a primary key in one table that is embedded in another (or the same) table. In the example given below, doctor ID is the foreign key value in the patient instance. It allows the implementation in a DBMS of the association shown in the class diagram above. The diagram below shows exactly how.

Exercise 17 Converting Classes/instances to tables/records

Re-draw the instance instances of the one to many situation shown above as records in two tables.

Many to Many Relationship Now for the more complex situation. The one to many situation described above is rather restrictive as some patients may have more than one doctor. In other words the above model does not cater for all situations that could occur. The solution is to create a separate table to link the two called a resolution table. This does not affect the instance diagram as it is not really necessary to show the table required in the database to solve the problem. However, some people do prefer you to do this, and it may help you create the database.

Exercise 18 MCQs 1. When mapping a class to a database, what does it become? a. A record ai. A database schema aj. An ERD ak. A table definition al. An individual data item

2. When mapping an instance of a class (instance), what does it become? a. A record am. A database schema an. An ERD ao. A table definition ap. An individual data item

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 39 of 53 Health Informatics Class modelling with UML Exercise 19 Identifying foreign keys and associations This exercise requires you to consider the models below and indicate in which class the foreign key(s) will need to be added for implementation in a relational DBMS. This is not part of UML. 1. General Practitioner (GP) consultation model1:

2. The hospital model part A:

1 Answer: In patient object: Dr ID. In Episode object: Dr ID and Patient ID. In each of the diagnosis tables: episode ID. Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 40 of 53 Health Informatics Class modelling with UML 3. The hospital conceptual model part B (adapted from Open University M866 book 1 p52):

4. The hospital model part C (adapted from OU M866 book 1 p52): This example requires you to first pf all annotate the uml diagram to identify the type of association, from the narrative description before indicating where the foreign keys will be placed.

The above exercise concerning foreign keys was to get you to understand the concept. You would NOT normally display foreign keys in a UML class diagram. And therefore should not usually do this.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 41 of 53 Health Informatics Class modelling with UML aq. The Meaning of Relationships (Semantics) People get very excited by attributing a great deal of knowledge and meaning to databases. In the 1980s a great deal of research took place developing 'semantic models'. These were basically modelling techniques which had a wider range of modelling symbols, such as inheritance, which we have come across in instance oriented modelling. The standard semantics of models are entities (classes), properties (attributes or fields), relationships and subtypes (Date p.350). Therefore, the meaning -- or rather the semantics -- of the model are these elements, nothing more and nothing less. Date 1995 (p346 - 371), provides for this area of work an unusually lucid account of semantic modelling (i.e. what we have been doing in this chapter with the models). The term Ontologies has been used by the Artificial Intelligence (AI) community to describe these more complex models, which also include a controlled vocabulary. You can find a good introduction to the subject in Mustafa Jarrar’s PHd thesis at his web site http://www.starlab.vub.ac.be/staff/mustafa/ (unfortunately he seems to have recently removed the content and left the table of contents only); his article Data modelling versus Ontology engineering provides an alternate source at http://www.starlab.vub.ac.be/staff/mustafa/publications/ [JDM03]LNCS03_V1-11.pdf. Because no diagrammatic modelling technique can fully explain the complexity required in some databases, narratives are added which frequently take the form of sets of rules or constraints (e.g. if a patient is female and aged between 15 and 40 years, alert a doctor to take a cervical screening). They usually require programmers to implement, although a lot can be done with filtering out certain records and querying the records in some way. Such databases that contain these rules are frequently referred to as knowledge bases. Nowadays, though, the word is often used for any database regardless of its complexity. It is possible to derive the models we have been using from a set of narrative statements. Such statements have in the past been called predicates (Date p.97) but are now more commonly called business rules. We have been doing this in a very simple way by providing a set of sentences (a narrative) describing the instance model in each of the instance diagrams so far. The 'meaning' of the data is also closely related to the very important idea of 'functional dependency' -- basically, the dependency between various pieces of data (e.g. you can't have a blood result without first having a patient). This is closely related to a process known as normalisation, which provides a method to ensure the data is correctly structured in terms of functional dependency. These issues are considered in more detail in the Database section at http://www.robin-beaumont.co.uk/virtualclassroom/contents.htm ar. Inheritance Inheritance is a very powerful tool for organising what often appear to be very complex situations into something that is more manageable. When modelling a situation, this is one of the later actions that takes place after all the classes and associations have been quite thoroughly described. This process itself involves the development of several drafts. Inheritance is the process of inheriting data and/or activities from a parent (superclass) to that of a child class (subclass). An example would be the subclass male person who would inherit all the detail in the human superclass but add some of his/her own. Often the parent 'superclass' is something that exists in the model but not in the real world, although this does not have to be the case as in this example. When an instance of the parent class does not exist, it is known as an abstract class. Generalisation is just describing inheritance from the opposite perspective. The subclass is a specialization of the superclass and therefore the superclass is a generalisation of several subclasses. In a UML Class diagram you show inheritance by using either a single triangle or one for each (generalisation) line, but this can lead to confusion (see below for why this is the case).

Generalisation Sets From the above diagrams concerning various shapes it is possible to see that while it is helpful to show various generalisations it could also be confusing, Take for example:

Does this mean that a employee can not have male o female specific attributes / operations? Unfortunately it is not clear from the diagram that what we want to describe is that a person is either male or female and also has an employment status. This can be achieved by using Generalisation sets to redraw the diagram. Each generalisation set is given a name (i.e. gender and employment status). In the UML this is called the powertype classifier, but I wouldn’t worry about that too much.

However this can still be confusing for within a particular Generalisation set we might want to specify that an instance of person might possess characteristics of more than one subtype. This can be achieved by using Constraints.

Constraining Subclasses A constraint is a UML defined term that is shown in curly brackets { . . . .} near the inheritance triangle on the diagram. The constraint consists of two words, one from two mutually exclusive options. First two mutually exclusive options:  Complete – All children (i.e. subclasses) have been specified (whether or not shown). No additional children are expected.  Incomplete – Some children (i.e. subclasses) have been specified, but the list is known to be incomplete. There are additional children that are not yet in the model. This is a statement about the model itself. Note that this is not the same as the ellipsis, which states that additional children exist in the model but are not shown on the current diagram. Second two mutually exclusive options:  Disjoint – A class only inherits from one subclass within each Generalisation relationship.  Overlapping – A class can inherit from several subclasses within each Generalisation relationship. Let’s consider an example given in the UML 2.0 superstructure (p76). Person could have two Generalisation relationships: Manager or Staff. This would be disjoint because every instance of Person must either be a Manager or Staff. In contrast, Person could have two Generalisation relationships: Sales Person and Manager. This Generalisation set would not be disjoint because there are instances of Person which can be a Sales Person and a Manager. If no constraint is shown on the generalisation line, the Default is {incomplete, disjoint} (p.77 uml 2.0 superstructure).

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 43 of 53 Health Informatics Class modelling with UML Here are some more examples from the UML 2.0 Superstructure specification document:

And some more:

We end this section by considering a hospital example.

Inheritance - Hospital Example The diagram below considers the idea of a procedure in a hospital. Procedures can, for this example, be of two types: inpatient and outpatient. However, both have a subset of identical characteristics and only differ on a few. We therefore create a 'procedure' class that is neither an inpatient nor outpatient procedure but contains the common characteristics of both. This procedure class is therefore something that does not exist in terms of instances (instances) but provides the basis to create other classes which would have instances such as day case hernia or inpatient varicose vein operation. It is important to realise that any instance of Daycase Procedure will possess the ID, name, Description, Available to GPFH, and cost attributes in addition to (i.e. inherited from) those attributes in the daycase procedure class. So it would end up with ID, name, Description, Available to GPFH, cost and maximum a day attributes. The same situation applies to the operations. Let’s recap: The hollow triangle in the above diagram indicates that both inpatient and day case procedures are inherited from the procedure class. It can be read as 'is of type'. The above diagram can therefore be interpreted as: Procedure is of type inpatient OR day case Note the 'OR' in the above sentence. If we wished to replace it with an 'and' we would need to indicate it on the diagram. UML uses '{overlapping}'. The 'OR' situation is known as a disjoint situation whereas the 'and' situation is known as overlapping. OMT used a different symbol for this: a filled in triangle; UML does not. The text beside the triangle 'procedure type' is known as a discriminator and is an attribute (data) whose value differentiates between the subclasses. Often this data item is contained in the superclass. Additional subclasses not shown on a diagram because of space constraints can be indicated by three black circles:

· · · at the end of the association line. Rumbaugh (2005) also suggests you can just add another sub class called 'other' as well.

Exercise 20 Generalisation/Inheritance

Draw class diagrams showing inheritance in one or more of the following situations:

 Cake mix as superclass; define some subclasses

 Employee payment as a superclass; define some subclasses

 NHS provider unit as a superclass; define some subclasses

 A superclass of your own choice; define some subclasses

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 45 of 53 Health Informatics Class modelling with UML as. Encapsulation Encapsulation has two different but related meanings. Firstly, it is used to mean the idea of an instance/class, in the manner we have been describing it above. That is, something that has both data and actions (Blair, 1989 quoted in Appleby 1991; Programming language concepts and paradigms). It can also be used simply to mean 'information hiding', meaning that other instances have to ask permission of the instance before being allowed to see its data. However, both these uses have the same fundamental idea behind them: the data in an instance should not be directly accessible outside of the instance. For example, if another instance wishes to discover the waist measurement of the instance girl the requesting instance should not be able to just examine the value of the data item waist but request it via an activity of the girl instance such as 'request waist measurement'. Doing this, the girl instance has the ability to refuse. Often activities that provide some sort of information are called 'services'. Although this aspect of the instance paradigm is very important when it comes to actually writing the software, it is of little importance when beginning to model a system. Exercise 21 MCQs The following class diagram is of a prescription class. Formulation is to do with how the drug is prepared (e.g. tablet, paste etc). Administration route is the method of taking the drug (e.g. oral etc), and usage details are basically instructions for the patient besides administration route.

1. In the above diagram, which is the incorrect statement? a. A prescription has zero or more drug items. b. A medical device is related to zero or more prescriptions. c. Each drug item consists of usage, strength, administration route and formulation details. d. Each drug item can contain a single usage detail. e. A single drug item can be related to zero or more prescriptions. 2. In the above diagram, what does the symbol indicate? a. Usage details consist of one or more such sets of details. b. Usage details consist of zero or more such sets of details. c. Usage details are related to several other usage details. d. Usage details are not clearly defined. e. The relationship is ambiguous.

3. The "{complete}" indication means the following: a. A drug item must contain details of one or more of the following: usage, strength, administration and formulation details. b. A drug item must contain details of usage, strength, administration and formulation. c. A drug item is only 'complete' when it contains information about the frequency details. d. A drug item is only 'complete' when it contains information of usage, strength, administration and formulation. e. A drug item is also called a 'complete' item.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 46 of 53 Health Informatics Class modelling with UML at. Polymorphism This is another aspect of the 'instance' paradigm that is not so important during the modelling stage but more important during the software development stage.

Polymorphism means that activities with the same name can behave differently in different classes. For example, consider the above diagram of various procedure types. The inpatient procedure class has an activity called 'use inpatient services' and the outpatient procedure class has an activity called 'use outpatient services'. It would be possible to have both the activities called 'use services' and the individual instances taking care of what actually happened. The advantage of this would be that the hospital manager instance would then only need to send one message to both instances 'use services' rather than a different one to each. au. Larger models and using Case tools We have now covered the main characteristics of Instance Oriented Modelling. However, there are two additional concepts which are important in UML which need consideration: Packages and Stereotypes. Both of these concepts become more important in larger models or when one uses a case tool such as System Architect.

Packages A Package in UML is just a container. They are used to break up larger structures into more manageable bits. For example, if we tried to model the whole healthcare system we could divide it up into numerous packages possibly including medical services, financial management, research, community services etc. The System Architect case tool has a good tutorial which involves modelling a hotel business, where you divide the model into three separate packages: Reservations, Human Resources and Building Maintenance. In ERD modelling in System Architect they talk about ‘subject areas’ (see the SA advanced ERD tutorial) which are basically the same as UML packages. Packages can be represented three different ways, as illustrated in the abstract from the UML 2.0. infrastructure document below for a package called ‘Types’

When using case tools, the user interface often demands that you place each diagram / class etc. in a particular package, obviously with a small project you can simply call the package ‘the project’. However even with small projects where there are more than 20 classes it is often sensible to divide up the classes into different packages. People often get unduly nervous about packages. Just think of them as folders for keeping similar UML elements; after all, the visual icon does look like a Microsoft folder icon.

Stereotypes I have really included this subsection to prevent you from using them! Again this is a type of UML element which allows you to group others together. In this instance a stereotype is a special type of class which you cannot use on its own but which you can use as a basis for classes that you create in

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 47 of 53 Health Informatics Class modelling with UML your models. Each class that makes use of the Stereotype indicates this by including the name of the stereotype above its name. Three cases that make use of a stereotype called ‘user_interface’ (from Pender, p.9):

UML has a number of pre-defined Stereotypes you can use. However as I said above I would warn you against using Stereotypes unless you are going to become a UML guru. Fowler 2004, who always offers sensible advice, hints at this (p66) as well. What you think is a stereotype is usually just an abstract superclass. For example the class Employee might be used in a model of an institution showing all the types of employees, but will be represented as a particular subtype such as full-time employee or student etc.

Exercise 22 Developing packages

You should spend no more than 20 minutes on this task.

Suggest what packages you might consider for one or two of the scenarios in the scenarios document

You can find the document at: http://www.robin-beaumont.co.uk/virtualclassroom/contents.htm and follow the links.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 48 of 53 Health Informatics Class modelling with UML av. Exercises You have now covered the most important aspects of Instance Oriented Modelling, particularly that concerned with looking at the ‘What’ rather than ‘How’ aspect. To help you consolidate your knowledge I have provided a few exercises below.

Exercise 23 Developing a Class diagram from a narrative

You should spend no more than 20 minutes on this task.

Draw the Class diagram which is implied from the information given below:

 A dental practice has one or more dentists and zero or more dental nurses.

 Each dentist has zero or more clients.

 Each client receives zero or more treatment sessions.

 Each session has a cost associated with it.

Exercise 24 Developing a Class diagram for a logbook

You should spend no more than 120 minutes on this exercise.

Imagine you have been asked to develop an electronic logbook for a doctor to allow you to analyse the following:  Type of patients seen  Type of procedures you were involved in  Level of competence for each procedure  Success of the interventions you were involved with  Any other areas you might consider to be important

Using the knowledge you gained from the document “An Introduction to Class Relationship Diagrams (ERDs)” define and develop a possible set of Classes and associations.

When you are sufficiently happy with your Class diagram, if at all possible enter it into a case tool. If not, use a drawing tool, or as a last resort use the drawing tools in MS Word.

If you are not a clinician, imagine that you are one. (You may want to talk to one after completing this task!)

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 49 of 53 Health Informatics Class modelling with UML Exercise 25 Developing Class diagrams as a group exercise

It is all very well developing Class diagrams as a solitary activity. The real learning starts when you are doing it as a group.

Work as a group either face to face or using e-mail or a discussion board to carry out the following exercise.

Warning: Only choose one of the tasks below, and only spend a maximum of two hours on it.  Develop an instance model for a work experience logbook.  Consider developing a model for a prescription, which can consist of several different items.  Develop a model for the area in which you work from two different perspectives.

At the end of the task, discuss amongst yourselves how you might check that you all have an agreed shared understand of the model(s).

You might want to use a group working evaluation sheet.

Optional Exercise 26 Developing Class diagrams for patient advice leaflets

The three following exercises are related:

1. Obtain several patient advice leaflets and see if you can come up with some standard section headings for each of the leaflets. Attempt to find advice leaflets from different sources and of different types.

2. Consider what type of advice leaflets you would have if you possessed all the patient advice leaflets which have been developed.

3. Attempt to amalgamate the headings you developed from the leaflets you obtained into a primitive type which would only need a few additional headings for any particular advice leaflet. (Look back at the section on inheritance.)

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 50 of 53 Health Informatics Class modelling with UML aw. Summary After all the information and exercises that you should have done to get this far, you must feel quite exhausted! Let’s recap what has been covered:  Description of the key characteristics of instance oriented modelling  Details of Class diagrams  Experience of creating Class diagrams from narratives  Experience of indicating on Class diagrams the necessary foreign keys to implement them in a database  Discussion of the differences between UML and OMT Class diagrams  Discussion of Generalisation sets and how useful the concept is in developing Class diagrams  Introduction to Packages and Stereotypes To check exactly how much you have learned, you should go back to the learning outcomes at the beginning of this document and tick off those with which you feel happy. There are other areas of instance oriented modelling that has not been covered in this document. One important aspect is the dynamic (“How”) side of things. You will find details of this aspect in other documents at http://www.robin-beaumont.co.uk/virtualclassroom/contents.htm ax. References Alavi M Wetherbe J C 1991 Mixed prototyping and data modelling for information system design. IEEE software May 87 – 91. One of very few articles which uses an experimental design in place of the purely non experimental case study, to assess various methodologies. Bennett S, Skelton J, Lunn K, 2005 UML: Schaum’s outlines. ISBN 0-07-710741-1 £10.99 [A much improved second edition – no CD but what can you expect at this price] Bertalanffy Ludwig von 1968 [but still published] General System Theory; Foundations, Development, Applications. George Braziller New York. Blaha M Premerlani W 1998 Instance-oriented Modelling and design for Database applications; Includes UML. Prentice Hall Blaha M, Rumbaugh J, 2005 Instance-Oriented Modelling and Design with UML (International Edition ISBN: 0131968599) Prentice Hall An e-book version is available (at: http://www.safarix.com/ ISBN: 013132894-8 You can see quite a lot of the book from the free review sections. Checkland P 1981 Systems thinking: systems practice. John Wiley An excellent introduction to the history of systems analysis as well as introducing Checkland's own 'soft systems' methodology. Checkland P Scholes J 1990 Soft Systems Methodology in action John Wiley. This book includes a case study from the NHS. Date C J. 1995 (6th ed.) An introduction to database systems Fowler M Scott K 1998 UML distilled: Applying the standard instance language. Addison Wesley Friedman A L Cornford DS 1989 Computer Systems Development: History, organisation and implementation. John Wiley. A wonderful book, excellent references, clear penetrating insights. etc. Klein H K Hirschheim R A 1987 A Comparative Framework of Data Modelling Paradigms and Approaches. The Computer Journal 30 1 9 - 15. Martin James 1989 - 1990 Information Engineering 3 volumes now published by Prentice Hall. The classic texts concerned with business process analysis. Very easy to read. £30 each volume. Moves from information strategy planning through business area analysis, technology impact analysis, to low level design. Firmly based in the business process paradigm. Newman M. Rosenberg D. 1985 Systems analysts and the politics of organisational control OMEGA int. j. of mgmt sci., 13 (5) 393 - 406 Open University 1993 Relational Database Systems M866 (Five books; Introduction to database technology, The Relational Modal, Normalisation, Using SQL, SQL database management) [These are excellent resources with many exercises and clear concise explanations].

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 51 of 53 Health Informatics Class modelling with UML Pender A Thomas 2002 UML weekend crash course. Wiley publishing inc. Reingruber Michael C. Gregory William W 1994 The Data Modelling Handbook John Wiley & Sons Chichester Rumbaugh J, Blaha M, Premerlani W et al 1991 Instance-Oriented Modelling and Design. Prentice Hall. See Blaha, Rumbaugh J, 2005 Schmuller Joseph 2004 Sams Teach Yourself UML in 24 hrs ISBN 0-672-3260-40 Third edition. [This new edition has a CD containing a pdf version of the book and a Case Tool called Poseidon (no time limit). Costs around £20] Tsang C H K, Lau C S W, Leung Y K, 2005 Instance-Oriented Technology ISBN: 0071240462 McGraw-Hill Education [rather overly concerned with programming for this course however it does come with a CD of the case tool VP-UML but the book is not on the disk] Joubert M The Use of Conceptual Graphs for Knowledge Bases, Customisation and Actual Data Organisation, Unpublished project working paper (AIM NUCLEUS) Wood-Harper AT Fitzgerald G 1982 A Taxonomy of Current Approaches to Systems Analysis The Computer Journal 25 1 12 - 16. Yourden 1989 Modern structured analysis Prentice hall. One of the standard texts on structured analysis again from the business process paradigm. ay. Web Links An excellent glossary of UML and instance modelling terms can be found at: http://www.csci.csusb.edu/dick/samples/uml.glossary.html The relative link also contains a good example of a teacher/student/course class model at http://www.csci.csusb.edu/cs202/uml1.html Links to most UML sources including all reference documents including most current as well as introductory tutorials: http://www.rational.com/uml/resources/documentation/index.jtmpl Quick reference guide to UML: http://www.rational.com/uml/resources/quick/index.jtmpl Instance Modelling group - International body responsible for setting OO standards: http://www.omg.org Alistair Cockburn's stuff on use cases: http://alistair.cockburn.us/crystal/articles/sucwg/structuringucswithgoals.htm The UML bibliography: http://www.db.informatik.uni-bremen.de/umlbib/

Past student's recommendations: A quick introduction to UML: http://bdn.borland.com/article/0,1410,31863,00.html#use-case-diagram Class and sequence diagram guidelines and more: http://www.agilemodeling.com/style/classDiagram.htm http://www.agilemodeling.com/artifacts/sequenceDiagram.htm

All above links were active on 18/03/2007.

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 52 of 53 Health Informatics Class modelling with UML Appendix - OMT

Robin Beaumont [email protected] 01/06/18 D:\Docs\2018-04-30\00915895dd971d56cf5e986a4751a0ff.docx Page 53 of 53