Paper No: 07 Information Storage and Retrieval Principal Investigator Dr. Jagdish Arora, Director Module : 03 Database& Management Systems Subject Coordinator INFLIBNET Centre, Gandhinagar Development Team PrincipalPaper Coordinator Investigator Dr. Jagdish Arora, Director & INFLIBNET Centre, Gandhinagar Subject Coordinator Content Writer Prof Devika P Madalli, Professor, Documentation Paper Coordinator Content Reviewer Research and Training Centre (DRTC), Bangalore Dr Aditya Tripathi, Content Writer Assistant Professor, Banaras Hindu University Prof Devika P Madalli, Professor, Documentation Content Reviewer Research and Training Centre (DRTC), Bangalore PaperContent Coordinator Reviewer Database Management System I. Objectives The main objective of this module is to: • Introduce the concepts of data, information and knowledge. • Introduce to the students, the meaning and characteristics of Information Retrieval(IR). • Provide definitions and describe various concepts, components and designing Issues of IR system. • Introduce to the students features and importance of DBMS and brief overview of SQL. • Familiarize the reader about different data models. • Introduce the functions and designing criteria of IR system for storing and retrieving the information. • Brief students about various standards and protocols which are used in IR. II. Learning Outcome After reading this module: • The students will gain the knowledge of Data, Information, knowledge also understand the importance of information in the era of ICT • The students will gain the knowledge of IR and also understand the benefits and issues information retrieval system for accessing and maintaining information. • The students will gain knowledge of database, it’s properties and types(i.e. Hierarchical Database, Relational Database, etc.) • The reader will gain the knowledge of ACID (Atomicity, Consistency, Isolation, and Durability) property, which is very useful in the processing of database transactions. • The students will understand the various data models. For instance E-R model to describe the data and relationship with other entities, etc. • The reader will gain the knowledge of different database languages( like DDL,DML,DCL, etc) and their uses. • Student is updated about various information storage and retrieval systems (e.g. user interface system, Query processing system, Database model system, etc) for storage and retrieval of information. • The reader will understand “what exactly Retrieval Status Value indicates?” and different methods/models which are used for evaluating the retrieval status value. • The reader will also gain the knowledge of vector space model, probabilistic model, Boolean model which are used in IR. III. Structure 1. Introduction 1.1 Database Management Systems 1.2 Advantages of DBMS’ 2. ACID Property 3. Data Models 3.1 Object-based logical model 3.2 Record-based logical model 4. DBMS Languages 4.1 Data Definition Language (DDL) 4.2 Data Manipulation Language (DML) 4.3 Data Control Language (DCL) 4.4 Brief Overview about Structured Query Language (SQL) 5. References 1. Introduction A database is the large, persistent, integrated collection of dynamic data that provides some operations to describe, establish, manipulate and access this data. ‘Data’ is derived from the latin word ‘datum’ meaning (thing) ‘given’ [wikipedia]. The main aim of a database is recording and maintaining information. The Chambers Science and Technology Dictionary defines the database as “a collection of structured data independent of any particular application”. The Macmillan Dictionary of Information Technology defines database as “a collection of interrelated data stored so that it may be accessed by users with simple user-friendly dialogues.” Traditional database are organized by fields records and file; File, Records and Fields: • File – A file is a collection of records. A file contains many records. In computer data is stored inside a file. • Record- It is a group of related information. Record is the unit of information in a database. It is generally what users want while searching a database. Each unit of information in a database is known as record. For example, a book card of library catalogue which describes title, author subject etc. of the book. A record is composed of fields and subfields. • Field- It is the collection of simple data values like integer, real text etc. In other words we can say that field is a pointer to record. Fields are the elements of information or particular segments which form the records. The items described in the book card of a library catalogue such as title, author etc. are the examples of field. For example, a telephone book is analogous to a file. It contains a list of records, each of which consists of three fields: name, address and telephone number. Hence, Database is a collection of structured records. However, the structure of a record is predefined so that data can be easily searched or accessed. Normally, records in database are arranged in a systematic order and bear unique identification. A record contains structured data. The format of the data stored in the record is predefined and uniform across all the records. This helps in locating the data in the records as well as in the database. The data structure is defined through field definition while designing the database. The fields contain the data and hence they are the leaf element in database structuring. The simplest form of a database is a Table. Fig.1: Sample Table 1.1 Database Management Systems What is DBMS (Database Management System)? A database management system (DBMS) is a computer program designed to manage a database, a large set of structured data and run operations on the data requested by numerous users. It is a collection of interrelated data and a set of programs to access or manipulate data. It consists of related data within an implicit meaning and hence is a database. A database management system (DBMS) is a collection of programs that enables users to create and maintain a database. According to the ANSI/SPARC DBMS Report (1977), a DBMS should be envisioned as a multi-layered system: External level (individual user views) Conceptual level (enterprise-wide views) Internal level (storage views) Storage level (physical storage) Fig.2: Database Management System 1.2 Advantages of DBMS i. Data independence: The DBMS can provide an abstract view of the data insulated application codes from details of data representation and storage ii. Efficient data access: DBMS utilizes a variety of sophisticated techniques to store and retrieve data efficiency. This feature is especially important if data is stored on external storage device. iii. Data integrity and security: DBMS can enforce integrity constraints on the data, if data is accessed through DBMS. It also enforces access controls that govern what data is visible to different classes of users. iv. Data administration: A DBMS facilitates maintenance and administration task for a large collection of data shared by several users. A good database administrator can effectively shields end-users from the chores of fine-tuning the data representation, periodic back-ups, etc. v. Reduced application development time: A database management system can reduce the application development time of database as well as maintenance of huge collection of data. 2. ACID Property ACID stands for Atomicity, Consistency, Isolation, and Durability. In context of databases, ACID is the property that guarantees the reliable processing of database transaction. This property is defined by Jim Gray in 1970s and he also developed the technologies for automatic achievement of these properties. • Atomicity: It is an all-or-none proposition • Consistency: It guarantees that database never leaves the transaction in half-finished state. • Isolation: It keeps transaction separated from each other until they are finished. • Durability: It guarantees that the database will keep track of pending changes in such way that the server can recover from an abnormal termination. The database developers always keep some rules and characteristics in their mind while developing the transaction system. The developers of the components that comprise the transaction are assured that these characteristics are in place. They do not need to manage these characteristics themselves. 3. Data Models Data Model consists of components which describes data, data relationships, data semantics and constraints. There are basically two types of data models which are further divided into different models: 3.1 Object-based logical model a) Entity-relationship model The Entity – Relationship model is based on entities and their relations. An entity can be anything living or non-living. In other words, an entity is any kind of object. For example, table, chair, students, teachers etc. Each entity in the world has certain characteristics or features which are known as Attributes. Same attributes can be manifested in more than one entity or objects. Such group of entities with same kind of attributes make a Set of Entities. For example, a class room of students is a Set of Entities as it carries students who have same kind of competency level, they study same subjects and they are offered same course. Each student of the class will also have a role number, name, age and so on. Attributes are expressed as fields of a database. These attributes of the students could be simple attributes as it holds plain value like the name of a person or the class role number.