DATABASE SYSTEM CONCEPTS AND ARCHITECTURE

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1 DATABASE SYSTEM CONCEPTS AND ARCHITECTURE 1 C H A P T E R 2

2 Contents Data Models, Schemas, and Instances Categories of Data Models Schemas, Instances, and Database State Three Schema Architecture and Data Independence Database languages DBMS Interfaces The Database System Environment 2

3 Data Model, Schemas and Instances The data model is a collection of concepts that can be used to describe the structure of a database, provides necessary means to achieve this abstraction. By structure of a database we mean data types, relationships, and constraints that hold a database. 3

4 Categories of Data Model High-level or conceptual data model Provide concepts that are close to the way many users perceive data. Low level or physical data model 4 Provides concepts that describe the details of how data is stored in the computer Representational or implementational data model Provide concepts that may be understood by user, but that are not too far removed from the way data is organized within the computer.

5 Schemas,Instances and database State It is important to distinguish between the description of the database and the database itself. The description of a database is called the database schema which is specified during database design and is not expected to change frequently The actual data in a database may change quite frequently and is called a database state or snapshot. 5

6 3Schema Architecture 6

7 3 Schema Architecture Internal Level has internal schema, which describes the physical storage structure of the database. Conceptual Level has conceptual schema, and hides the physical storage structures and concentrates on describing entities, data types, relationships, user operations and constraints. External or View Level describes a part of the database that is particular to a group of users interest in it and hides the rest of the database from that user group. 7

8 Data Independence Logical Data Independence Capacity to change the conceptual schema without changing the application programs or external schema. Physical data independence 8 Capacity to change the internal schema without changing the conceptual schema

9 DDL DBMS Languages Used by DBA and Database designers to define both conceptual and internal schemas. Storage Definition Language (sdl): used to define the internal schema View Definition Language(VDL): used to specify the user views and their mapping to the conceptual schema. DML( data manipulation language): for retrieval, insertion,deletion and modification of the data. 9

10 Interfaces Menu based Interfaces Forms-based Interfaces Graphical User Interfaces Natural Language Interfaces Interfaces for Parametric Users Interfaces for DBA 10

11 The Database System Environment 11

12 Classification of Database Management System Several criteria are normally used to classify DBMS s Data Model Number of Users Number of Sites Cost 12

13 One place for all your IT Needs Computer Languages Website Development Project Development Software Development Corporate Training 13 Contact: 3B, Hilltop Residency, Girnar Hills Opp Gomatesh School, Hindwadi Belgaum Phone: ,

Introduction to Database Technology Elmasri/Navathe ch 1-2 Padron-McCarthy/Risch ch 1 Sobhan Badiozamany Silvia Stefanova Department of Information Te

Introduction to Database Technology Elmasri/Navathe ch 1-2 Padron-McCarthy/Risch ch 1 Sobhan Badiozamany Silvia Stefanova Department of Information Te DATABASE DESIGN I - 1DL300 Spring 2013 An Introductory Course on Database Systems http://www.it.uu.se/edu/course/homepage/dbastekn/vt13/ Uppsala Database Laboratory Department of Information Technology,