DOCSLIB.ORG

Entity-Relationship Model

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Entity-Relationship Model Database The Entity Relationship Model Management Peter Wood Overview Entities Attributes Relationships I An example of a conceptual (high-level) data model Weak Entity Types I Useful for design before moving to a lower level ISA relationships model (e.g. relational) I Alternatives include I UML (Unified Modelling Language) and I ODL (Object Description Language) Database Modelling Steps Management Peter Wood S Overview S ¡ Entities aspects of SS ¡ Attributes ¡ the real world ¡ ¡ Relationships h¡ hh ((¡ hhh((( Weak Entity Types ISA relationships manual modeling ? conceptual schema (ER schema) Z Z Z semi-automatic Z transformation Z Z = ? ZZ~ relational network object oriented schema schema schema I Integrity constraints I primary keys for entity types and relationship types, and I multiplicity (cardinality) constraints for relationship types I The ER model is only a partial data model, since it has no standard manipulative part Database The Components of the ER Model Management Peter Wood Overview Entities I Structural part Attributes I entity types Relationships I attributes Weak Entity Types I relationship types ISA relationships I The ER model is only a partial data model, since it has no standard manipulative part Database The Components of the ER Model Management Peter Wood Overview Entities I Structural part Attributes I entity types Relationships I attributes Weak Entity Types I relationship types ISA relationships I Integrity constraints I primary keys for entity types and relationship types, and I multiplicity (cardinality) constraints for relationship types Database The Components of the ER Model Management Peter Wood Overview Entities I Structural part Attributes I entity types Relationships I attributes Weak Entity Types I relationship types ISA relationships I Integrity constraints I primary keys for entity types and relationship types, and I multiplicity (cardinality) constraints for relationship types I The ER model is only a partial data model, since it has no standard manipulative part Database The Main Advantages of the ER Model Management Peter Wood Overview Entities Attributes Relationships The diagrams (ERDs) associated with entity-relationship Weak Entity Types models ISA relationships I are relatively simple I are user-friendly I can provide a unified view of data, which is independent of any implemented data model Database The Building Blocks of an ERD Management Peter Wood Overview Entities and entity types (entity sets) I Entities I Relationships and relationship types Attributes I Attributes, keys and roles Relationships Weak Entity Types ISA relationships Database Entities and Entity Types Management Peter Wood Overview An entity is a “thing” that exists and can be uniquely Entities Attributes identified, e.g., an individual person. Relationships Weak Entity Types An entity type (or entity set) is a collection of similar ISA relationships entities, e.g., a collection of people. An entity type I is similar to a class in object-oriented languages I has associated attributes, which represent properties of the entities comprising the entity type I is represented in an ERD by a rectangle Database Attributes Management Peter Wood Overview Entities Attribute names (or simply attributes) are properties of Attributes entity types. Relationships Weak Entity Types ISA relationships I Each attribute usually has only simple values (e.g. integers or character strings) I represented by an oval in an ERD, with a line to the rectangle representing its entity type I Sometimes multi-valued attributes (e.g. Phones) are allowed I represented by a double oval in an ERD Database Example of Entity Type and Attributes Management Peter Wood Overview Entities Attributes Name Address Relationships Weak Entity Types ISA relationships NI# Person Phones I Each Person has a single Name, Address and National Insurance number (NI#) I Each Person can have many Phones Database Domain Management Peter Wood Overview Entities Attributes The domain of an attribute of an entity type is the set of Relationships constant values associated with that attribute. Weak Entity Types ISA relationships Domains can be I atomic such as the domain of integers or the domain of strings, or I set-valued such as the domain of finite sets of integers or of finite sets of strings. Database Relationship Types Management A relationship type is an association between two or more Peter Wood entity types. Overview Entities Attributes Relationship types are represented in an ERD by I Relationships diamond shapes, Weak Entity Types I with lines to each of the rectangles representing ISA relationships entity types involved in the association Example of a relationship type Teaches between entity type Lecturer and entity type Student: Lecturer Teaches Student Database Relationships Management A relationship is an instance of a relationship type, i.e., it Peter Wood is the set of associations between the entities comprising Overview the entity types associated by the relationship type. Entities Attributes Relationships Weak Entity Types ISA relationships I Above diagram is not an ERD I Entities for one entity type on left (green) I Entities for another entity type on right (red) I Lines between entities show the relationship Database Multiplicity Constraints in Relationship Types Management Peter Wood Overview Entities Attributes I many-to-one (or one-to-many) Relationships An Employee Works in one Department or a Weak Entity Types Department has many Employees. ISA relationships I one-to-one A Manager Heads one Department and vice versa. I many-to-many A Lecturer Teaches many Students and a Student is Taught by many Lecturers. Database Example of many-to-one relationship type Management Peter Wood Overview Entities Attributes Relationships Employee Works-in Department Weak Entity Types ISA relationships The arrowhead is drawn at the “one” end of the relationship type I Each Employee Works-in one Department I Each Department has many Employees working in it Database Example of many-to-one relationship Management Peter Wood Overview Entities Attributes Relationships Weak Entity Types ISA relationships Database Example of one-to-one relationship type Management Peter Wood Overview Entities Attributes Relationships Weak Entity Types Manager Occupies Office ISA relationships The arrowhead is drawn at both ends of the relationship type I Each Manager Occupies one Office I Each Office has one Manager occupying it Database Example of one-to-one relationship Management Peter Wood Overview Entities Attributes Relationships Weak Entity Types ISA relationships Database Example of many-to-many relationship type Management Peter Wood Overview Entities Attributes Relationships Weak Entity Types Lecturer Teaches Student ISA relationships No arrowheads are drawn I Each Lecturer Teaches many Students I Each Student is taught by many Lecturers Database Example of many-to-many relationship Management Peter Wood Overview Entities Attributes Relationships Weak Entity Types ISA relationships Database Multiple relationship types Management There may be more than one relationship type between Peter Wood two entity types. Overview Entities Attributes Relationships Teaches Weak Entity Types ISA relationships Lecturer Student Tutors I Teaches relationship type is many-to-many I Tutors relationship type is one-to-many (from Lecturer to Student) Database Participation Constraints in Relationships Management Peter Wood Overview I optional relationship Entities I e.g., an Employee may or may not be assigned to a Attributes Department Relationships I Participation of entity (e.g., Employee) in relationship Weak Entity Types is said to be partial ISA relationships I This is the default for relationships in our notation I (Sometimes indicated by cardinality constraint of 0..*) I mandatory relationship I e.g., every Course must be Taught by at least one Lecturer I Participation of entity (e.g., Course) in relationship said to be total I Indicated by double lines in our notation I (Sometimes indicated by cardinality constraint of 1..*) Database Example of Participation Constraints Management Peter Wood Overview Entities Lecturer Teaches Student Attributes Relationships Weak Entity Types ISA relationships I Some Lecturers may not Teach any Students I Each Student must be taught by at least one Lecturer 0..* 1..* Lecturer Teaches Student Database Binary Versus Multiway Relationship Types Management Peter Wood Overview Entities Attributes Supplier Supplies Part Relationships Weak Entity Types ISA relationships Project I each supplier may supply different parts to different projects I Supplies is an example of a ternary relationship type Database Keys and Superkeys Management Peter Wood Definition of a superkey. A set of attributes of an entity Overview type is a superkey if for each entity, say e, over that type, Entities the set of values of the attributes in the superkey uniquely Attributes identifies e. Relationships e.g., a Person may be uniquely identified by {Name, NI#} Weak Entity Types ISA relationships Definition of a key. A key for an entity type is a superkey which is minimal. e.g., to uniquely identify a Person, NI# is sufficient I simple keys are single attribute keys, such as Emp# and NI#. I composite keys are keys having more than one attribute, such as {Department, University} and {Name, Address}. Database Management Definition of primary key of an entity type. A primary Peter Wood key is a key that has been designated as such by the database designer. Overview Entities Attributes I The primary
Load more

Recommended publications
  • Data Model Standards and Guidelines, Registration Policies And
    Data Model Standards and Guidelines, Registration Policies and Procedures Version 3.2 ● 6/02/2017 Data Model Standards and Guidelines, Registration Policies and Procedures Document Version Control Document Version Control VERSION D ATE AUTHOR DESCRIPTION DRAFT 03/28/07 Venkatesh Kadadasu Baseline Draft Document 0.1 05/04/2007 Venkatesh Kadadasu Sections 1.1, 1.2, 1.3, 1.4 revised 0.2 05/07/2007 Venkatesh Kadadasu Sections 1.4, 2.0, 2.2, 2.2.1, 3.1, 3.2, 3.2.1, 3.2.2 revised 0.3 05/24/07 Venkatesh Kadadasu Incorporated feedback from Uli 0.4 5/31/2007 Venkatesh Kadadasu Incorporated Steve’s feedback: Section 1.5 Issues -Change Decide to Decision Section 2.2.5 Coordinate with Kumar and Lisa to determine the class words used by XML community, and identify them in the document. (This was discussed previously.) Data Standardization - We have discussed on several occasions the cross-walk table between tabular naming standards and XML. When did it get dropped? Section 2.3.2 Conceptual data model level of detail: changed (S) No foreign key attributes may be entered in the conceptual data model. To (S) No attributes may be entered in the conceptual data model. 0.5 6/4/2007 Steve Horn Move last paragraph of Section 2.0 to section 2.1.4 Data Standardization Added definitions of key terms 0.6 6/5/2007 Ulrike Nasshan Section 2.2.5 Coordinate with Kumar and Lisa to determine the class words used by XML community, and identify them in the document.
    [Show full text]
  • Using Telelogic DOORS and Microsoft Visio to Model and Visualize Complex Business Processes
    Using Telelogic DOORS and Microsoft Visio to Model and Visualize Complex Business Processes “The Business Driven Application Lifecycle” Bob Sherman Procter & Gamble Pharmaceuticals [email protected] Michael Sutherland Galactic Solutions Group, LLC [email protected] Prepared for the Telelogic 2005 User Group Conference, Americas & Asia/Pacific http://www.telelogic.com/news/usergroup/us2005/index.cfm 24 October 2005 Abstract: The fact that most Information Technology (IT) projects fail as a result of requirements management problems is common knowledge. What is not commonly recognized is that the widely haled “use case” and Object Oriented Analysis and Design (OOAD) phenomenon have resulted in little (if any) abatement of IT project failures. In fact, ten years after the advent of these methods, every major IT industry research group remains aligned on the fact that these projects are still failing at an alarming rate (less than a 30% success rate). Ironically, the popularity of use case and OOAD (e.g. UML) methods may be doing more harm than good by diverting our attention away from addressing the real root cause of IT project failures (when you have a new hammer, everything looks like a nail). This paper asserts that, the real root cause of IT project failures centers around the failure to map requirements to an accurate, precise, comprehensive, optimized business model. This argument will be supported by a using a brief recap of the history of use case and OOAD methods to identify differences between the problems these methods were intended to address and the challenges of today’s IT projects.
    [Show full text]
  • Principles of the Concept-Oriented Data Model Alexandr Savinov
    Principles of the Concept-Oriented Data Model Alexandr Savinov Institute of Mathematics and Computer Science Academy of Sciences of Moldova Academiei 5, MD-2028 Chisinau, Moldova Fraunhofer Institute for Autonomous Intelligent System Schloss Birlinghoven, 53754 Sankt Augustin, Germany http://www.conceptoriented.com [email protected] Principles of the Concept-Oriented Data Model Alexandr Savinov Institute of Mathematics and Computer Science, Academy of Sciences of Moldova Academiei 5, MD-2028 Chisinau, Moldova Fraunhofer Institute for Autonomous Intelligent System Schloss Birlinghoven, 53754 Sankt Augustin, Germany http://www.conceptoriented.com [email protected] In the paper a new approach to data representation and manipulation is described, which is called the concept-oriented data model (CODM). It is supposed that items represent data units, which are stored in concepts. A concept is a combination of superconcepts, which determine the concept’s dimensionality or properties. An item is a combination of superitems taken by one from all the superconcepts. An item stores a combination of references to its superitems. The references implement inclusion relation or attribute- value relation among items. A concept-oriented database is defined by its concept structure called syntax or schema and its item structure called semantics. The model defines formal transformations of syntax and semantics including the canonical semantics where all concepts are merged and the data semantics is represented by one set of items. The concept-oriented data model treats relations as subconcepts where items are instances of the relations. Multi-valued attributes are defined via subconcepts as a view on the database semantics rather than as a built-in mechanism.
    [Show full text]
  • Metamodeling the Enhanced Entity-Relationship Model
    Metamodeling the Enhanced Entity-Relationship Model Robson N. Fidalgo1, Edson Alves1, Sergio España2, Jaelson Castro1, Oscar Pastor2 1 Center for Informatics, Federal University of Pernambuco, Recife(PE), Brazil {rdnf, eas4, jbc}@cin.ufpe.br 2 Centro de Investigación ProS, Universitat Politècnica de València, València, España {sergio.espana,opastor}@pros.upv.es Abstract. A metamodel provides an abstract syntax to distinguish between valid and invalid models. That is, a metamodel is as useful for a modeling language as a grammar is for a programming language. In this context, although the Enhanced Entity-Relationship (EER) Model is the ”de facto” standard modeling language for database conceptual design, to the best of our knowledge, there are only two proposals of EER metamodels, which do not provide a full support to Chen’s notation. Furthermore, neither a discussion about the engineering used for specifying these metamodels is presented nor a comparative analysis among them is made. With the aim at overcoming these drawbacks, we show a detailed and practical view of how to formalize the EER Model by means of a metamodel that (i) covers all elements of the Chen’s notation, (ii) defines well-formedness rules needed for creating syntactically correct EER schemas, and (iii) can be used as a starting point to create Computer Aided Software Engineering (CASE) tools for EER modeling, interchange metadata among these tools, perform automatic SQL/DDL code generation, and/or extend (or reuse part of) the EER Model. In order to show the feasibility, expressiveness, and usefulness of our metamodel (named EERMM), we have developed a CASE tool (named EERCASE), which has been tested with a practical example that covers all EER constructors, confirming that our metamodel is feasible, useful, more expressive than related ones and correctly defined.
    [Show full text]
  • The Importance of Data Models in Enterprise Metadata Management
    THE IMPORTANCE OF DATA MODELS IN ENTERPRISE METADATA MANAGEMENT October 19, 2017 © 2016 ASG Technologies Group, Inc. All rights reserved HAPPINESS IS… SOURCE: 10/18/2017 TODAY SHOW – “THE BLUE ZONE OF HAPPINESS” – DAN BUETTNER • 3 Close Friends • Get a Dog • Good Light • Get Religion • Get Married…. Stay Married • Volunteer • “Money will buy you Happiness… well, it’s more about Financial Security” • “Our Data Models are now incorporated within our corporate metadata repository” © 2016 ASG Technologies Group, Inc. All rights reserved 3 POINTS TO REMEMBER SOURCE: 10/19/2017 DAMA NYC – NOONTIME SPEAKER SLOT – MIKE WANYO – ASG TECHNOLOGIES 1. Happiness is individually sought and achievable © 2016 ASG Technologies Group, Inc. All rights reserved 3 POINTS TO REMEMBER SOURCE: 10/19/2017 DAMA NYC – NOONTIME SPEAKER SLOT – MIKE WANYO – ASG TECHNOLOGIES 1. Happiness is individually sought and achievable 2. Data Models can in be incorporated into your corporate metadata repository © 2016 ASG Technologies Group, Inc. All rights reserved 3 POINTS TO REMEMBER SOURCE: 10/19/2017 DAMA NYC – NOONTIME SPEAKER SLOT – MIKE WANYO – ASG TECHNOLOGIES 1. Happiness is individually sought and achievable 2. Data Models can in be incorporated into your corporate metadata repository 3. ASG Technologies can provide an overall solution with services to accomplish #2 above and more for your company. © 2016 ASG Technologies Group, Inc. All rights reserved AGENDA Data model imports to the metadata collection View and search capabilities Traceability of physical and logical
    [Show full text]
  • Towards the Universal Spatial Data Model Based Indexing and Its Implementation in Mysql
    Towards the universal spatial data model based indexing and its implementation in MySQL Evangelos Katsikaros Kongens Lyngby 2012 IMM-M.Sc.-2012-97 Technical University of Denmark Informatics and Mathematical Modelling Building 321, DK-2800 Kongens Lyngby, Denmark Phone +45 45253351, Fax +45 45882673 [email protected] www.imm.dtu.dk IMM-M.Sc.: ISSN XXXX-XXXX Summary This thesis deals with spatial indexing and models that are able to abstract the variety of existing spatial index solutions. This research involves a thorough presentation of existing dynamic spatial indexes based on R-trees, investigating abstraction models and implementing such a model in MySQL. To that end, the relevant theory is presented. A thorough study is performed on the recent and seminal works on spatial index trees and we describe their basic properties and the way search, deletion and insertion are performed on them. During this effort, we encountered details that baffled us, did not make the understanding the core concepts smooth or we thought that could be a source of confusion. We took great care in explaining in depth these details so that the current study can be a useful guide for a number of them. A selection of these models were later implemented in MySQL. We investigated the way spatial indexing is currently engineered in MySQL and we reveal how search, deletion and insertion are performed. This paves the path to the un- derstanding of our intervention and additions to MySQL's codebase. All of the code produced throughout this research was included in a patch against the RDBMS MariaDB.
    [Show full text]
  • HANDLE - a Generic Metadata Model for Data Lakes
    HANDLE - A Generic Metadata Model for Data Lakes Rebecca Eichler, Corinna Giebler, Christoph Gr¨oger, Holger Schwarz, and Bernhard Mitschang In: Big Data Analytics and Knowledge Discovery (DaWaK) 2020 BIBTEX: @inproceedingsfeichler2020handle, title=fHANDLE-A Generic Metadata Model for Data Lakesg, author=fEichler, Rebecca and Giebler, Corinna and Gr{\"o\}ger,Christoph and Schwarz, Holger and Mitschang, Bernhardg, booktitle=fInternational Conference on Big Data Analytics and Knowledge Discovery (DaWaK) 2020g, pages=f73{88g, year=f2020g, organization=fSpringerg, doi=f10.1007/978-3-030-59065-9 7g g c by Springer Nature This is the author's version of the work. The final authenticated version is avail- able online at: https://doi.org/10.1007/978-3-030-59065-9 7 HANDLE - A Generic Metadata Model for Data Lakes Rebecca Eichler1, Corinna Giebler1, Christoph Gr¨oger2, Holger Schwarz1, and Bernhard Mitschang1 1 University of Stuttgart, Universit¨atsstraße38, 70569 Stuttgart, Germany [email protected] 2 Robert Bosch GmbH, Borsigstraße 4, 70469 Stuttgart, Germany [email protected] Abstract The substantial increase in generated data induced the de- velopment of new concepts such as the data lake. A data lake is a large storage repository designed to enable flexible extraction of the data's value. A key aspect of exploiting data value in data lakes is the collec- tion and management of metadata. To store and handle the metadata, a generic metadata model is required that can reflect metadata of any potential metadata management use case, e.g., data versioning or data lineage. However, an evaluation of existent metadata models yields that none so far are sufficiently generic.
    [Show full text]
  • XV. the Entity-Relationship Model
    Information Systems Analysis and Design csc340 XV. The Entity-Relationship Model The Entity-Relationship Model Entities, Relationships and Attributes Cardinalities, Identifiers and Generalization Documentation of E-R Diagrams and Business Rules 2002 John Mylopoulos The Entity-Relationship Model -- 1 Information Systems Analysis and Design csc340 The Entity Relationship Model The Entity-Relationship (ER) model is a conceptual data model, capable of describing the data requirements for a new information system in a direct and easy to understand graphical notation. Data requirements are described in terms of a conceptualconceptual (or, ER) schema. ER schemata are comparable to class diagrams. 2002 John Mylopoulos The Entity-Relationship Model -- 2 Information Systems Analysis and Design csc340 The Constructs of the E-R Model AND/XOR 2002 John Mylopoulos The Entity-Relationship Model -- 3 Information Systems Analysis and Design csc340 Entities These represent classes of objects (facts, things, people,...) that have properties in common and an autonomous existence. City, Department, Employee, Purchase and Sale are examples of entities for a commercial organization. An instance of an entity is an object in the class represented by the entity. Stockholm, Helsinki, are examples of instances of the entity City, and the employees Peterson and Johanson are examples of instances of the Employee entity. The E-R model is very different from the relational model in which it is not possible to represent an object without knowing its properties (an employee is represented by a tuple containing the name, surname, age, and other attributes.) 2002 John Mylopoulos The Entity-Relationship Model -- 4 Information Systems Analysis and Design csc340 Examples of Entities 2002 John Mylopoulos The Entity-Relationship Model -- 5 Information Systems Analysis and Design csc340 Relationships They represent logical links between two or more entities.
    [Show full text]
  • Patterns for Slick Database Applications Jan Christopher Vogt, EPFL Slick Team
    Patterns for Slick database applications Jan Christopher Vogt, EPFL Slick Team #scalax Recap: What is Slick? (for ( c <- coffees; if c.sales > 999 ) yield c.name).run select "COF_NAME" from "COFFEES" where "SALES" > 999 Agenda • Query composition and re-use • Getting rid of boiler plate in Slick 2.0 – outer joins / auto joins – auto increment – code generation • Dynamic Slick queries Query composition and re-use For-expression desugaring in Scala for ( c <- coffees; if c.sales > 999 ) yield c.name coffees .withFilter(_.sales > 999) .map(_.name) Types in Slick class Coffees(tag: Tag) extends Table[C](tag,"COFFEES”) { def * = (name, supId, price, sales, total) <> ... val name = column[String]("COF_NAME", O.PrimaryKey) val supId = column[Int]("SUP_ID") val price = column[BigDecimal]("PRICE") val sales = column[Int]("SALES") val total = column[Int]("TOTAL") } lazy val coffees = TableQuery[Coffees] <: Query[Coffees,C] coffees(coffees.map ).map( :TableQuery(c => c.[Coffees,_]name) ).map( (c ) => ((c:Coffees) => (c.name ) : Column[String]) ): Query[Column[String],String] Table extensions class Coffees(tag: Tag) extends Table[C](tag,"COFFEES”) { … val price = column[BigDecimal]("PRICE") val sales = column[Int]("SALES") def revenue = price.asColumnOf[Double] * sales.asColumnOf[Double] } coffees.map(c => c.revenue) Query extensions implicit class QueryExtensions[T,E] ( val q: Query[T,E] ){ def page(no: Int, pageSize: Int = 10) : Query[T,E] = q.drop( (no-1)*pageSize ).take(pageSize) } suppliers.page(5) coffees.sortBy(_.name).page(5) Query extensions
    [Show full text]
  • HHS Logical Data Model Practices Guide
    DEPARTMENT OF HEALTH AND HUMAN SERVICES ENTERPRISE PERFORMANCE LIFE CYCLE FRAMEWORK <OIDV Logo> PPRRAACCTTIIICCEESS GGUUIIIDDEE LOGICAL DATA MODELING Issue Date: <mm/dd/yyyy> Revision Date: <mm/dd/yyyy> Document Purpose This Practices Guide is provides an overview describing the best practices, activities, attributes, and related templates, tools, information, and key terminology of industry-leading project management practices and their accompanying project management templates. Background The Department of Health and Human Services (HHS) Enterprise Performance Life Cycle (EPLC) is a framework to enhance Information Technology (IT) governance through rigorous application of sound investment and project management principles, and industry best practices. The EPLC provides the context for the governance process and describes interdependencies between its project management, investment management, and capital planning components. The EPLC framework establishes an environment in which HHS IT investments and projects consistently achieve successful outcomes that align with Department and Operating Division goals and objectives. A Logical Data Model (LDM) is a complete representation of data requirements and the structural business rules that govern data quality in support of project’s requirements. The LDM shows the specific entities, attributes and relationships involved in a business function and is the basis for the creation of the physical data model. Practice Overview A logical data model is a graphical representation of the business requirements. They describe the data that are important to the organization and how they relate to one another, as well as business definitions and examples. The logical data model is created during the Requirements Analysis Phase and is a component of the Requirements Document. The logical data model helps to build a common understanding of business data elements and requirements and is the basis of physical database design.
    [Show full text]
  • The Layman's Guide to Reading Data Models
    Data Architecture & Engineering Services The Layman’s Guide to Reading Data Models A data model shows a data asset’s structure, including the relationships and constraints that determine how data will be stored and accessed. 1. Common Types of Data Models Conceptual Data Model A conceptual data model defines high-level relationships between real-world entities in a particular domain. Entities are typically depicted in boxes, while lines or arrows map the relationships between entities (as shown in Figure 1). Figure 1: Conceptual Data Model Logical Data Model A logical data model defines how a data model should be implemented, with as much detail as possible, without regard for its physical implementation in a database. Within a logical data model, an entity’s box contains a list of the entity’s attributes. One or more attributes is designated as a primary key, whose value uniquely specifies an instance of that entity. A primary key may be referred to in another entity as a foreign key. In the Figure 2 example, each Employee works for only one Employer. Each Employer may have zero or more Employees. This is indicated via the model’s line notation (refer to the Describing Relationships section). Figure 2: Logical Data Model Last Updated: 03/30/2021 OIT|EADG|DEA|DAES 1 The Layman’s Guide to Reading Data Models Physical Data Model A physical data model describes the implementation of a data model in a database (as shown in Figure 3). Entities are described as tables, Attributes are translated to table column, and Each column’s data type is specified.
    [Show full text]
  • What Is a Metamodel: the OMG's Metamodeling Infrastructure
    Modeling and metamodeling in Model Driven Development What is a metamodel: the OMG’s metamodeling infrastructure Warsaw, May 14-15th 2009 Gonzalo Génova [email protected] http://www.kr.inf.uc3m.es/ggenova/ Knowledge Reuse Group Universidad Carlos III de Madrid What is a metamodel: the OMG’s metamodeling infrastructure 1 Structure of the seminar On the difference between What is a model: analysis and design syntax and semantics models What is a metamodel: Metamodeling directed the OMG’s metamodeling relationships in UML infrastructure By the way, what does this diagram mean, what is its syntax? What is a metamodel: the OMG’s metamodeling infrastructure 2 Sources • Jean Bézivin – Model Engineering for Software Modernization. • The 11th IEEE Working Conference on Reverse Engineering, Delft, November 8th-12th 2004. – On the unification power of models. • Software and Systems Modeling 4(2): 171–188, May 2005. • Colin Atkinson, Thomas Kühne – Model-Driven Development: A Metamodeling Foundation. • IEEE Software 20(5): 36-41, Sep-Oct 2003. – Reducing Accidental Complexity in Domain Models. • Software and Systems Modeling 7(3): 345-359, July 2008. • My own ideas and elaboration. What is a metamodel: the OMG’s metamodeling infrastructure 3 Table of contents 1. Introduction: definitions of metamodel 2. Representation and conformance 3. The four metamodeling layers 4. Metamodel and semantic domain 5. A case of metamodel/domain mismatch 6. Conclusions What is a metamodel: the OMG’s metamodeling infrastructure 4 Introduction: definitions of metamodel What is a metamodel: the OMG’s metamodeling infrastructure 5 What is a metamodel (according to Google definitions) • If someone still believes there is a commonly accepted definition..
    [Show full text]