Chapter 2 Database System Concepts and Architecture Outline
Chapter 2: Database System Concepts and Architecture Outline n n n n n Data Models and Their Categories History of Data Models Schemas, Instances, and States Three-Schema Architecture Data Independence DBMS Languages and Interfaces Database System Utilities and Tools Centralized and Client-Server Architectures Classification of DBMSs Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 1
Data Models n n n Data Model: n structure of a database, the operations for manipulating these structures, and certain constraints that the database should obey. Data Model Structure and Constraints: Data Model Operations: Categories of Data Models n Conceptual (high-level, semantic) data models: n (Also called entity-based or object-based data models. ) n Physical (low-level, internal) data models: n Implementation (representational) data models: ex: relational data model Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 2
Database Schema, Instance and State n n n n Database Schema: n Includes descriptions of the database structure, data types, and the constraints on the database. Schema Diagram: n An illustrative display of (most aspects of) a database schema. Schema Construct: n A component of the schema or an object within the schema, e. g. , STUDENT, COURSE. Database State: Distinction n The database schema changes very infrequently. n The database state changes every time the database is updated. Schema is also called intension. State is also called extension. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 3
Example of a Database Schema Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 4
Example of a database state STUDENT Name Student_number Class Major Smith 17 1 CS Brown 8 2 CS Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 5
Three-Schema Architecture n Defines DBMS schemas at three levels: n Internal schema n Conceptual schema: entities, data types, relationships, etc n External schemas at the external level to describe the various user views. n Usually uses the same data model as the conceptual schema. Data Independence: n Logical Data Independence: ability to change conceptual schema without effecting appl. programs n Physical Data Independence: ability to change internal schema without effecting upper layers Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 6
DBMS Languages n n Data Definition Language (DDL) Data Manipulation Language (DML) n High-Level or Non-procedural Languages: These include the relational language SQL n n May be used in a standalone way or may be embedded in a programming language. Also called declarative langauages Low Level or Procedural Languages: n These must be embedded in a programming language Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 7
DBMS Interfaces n n n Stand-alone query language interfaces n Example: Entering SQL queries at the DBMS interactive SQL interface (e. g. SQL*Plus in ORACLE) Programmer interfaces for embedding DML in programming languages User-friendly interfaces n Menu-based, forms-based, graphics-based, etc. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 8
DBMS Programming Language Interfaces n n n Embedded Approach: e. g embedded SQL (for C, C++, etc. ), SQLJ (for Java) Procedure Call Approach: e. g. JDBC for Java, ODBC for other programming languages Database Programming Language Approach: e. g. ORACLE has PL/SQL Menu-based, popular for browsing on the web Forms-based, designed for naïve users Graphics-based Natural language: requests in written English Combinations of the above: Speech as Input and Output Web Browser as an interface Parametric interfaces, e. g. , bank tellers using function keys. Interfaces for the DBA: Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 9
Database System Utilities n n To perform certain functions such as: n Loading data stored in files into a database. Includes data conversion tools. n Backing up the database periodically on tape. n Reorganizing database file structures. n Report generation utilities. n Performance monitoring utilities. Data dictionary / repository: Application Development Environments and CASE (computer-aided software engineering) tools: Examples: n Power. Builder (Sybase) n JBuilder (Borland) n Oracle SQL Developer, JDeveloper 10 G (Oracle) Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 10
Typical DBMS Component Modules Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 11
A Physical Centralized Architecture Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 12
Logical two-tier client server architecture Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 13
Three-tier client-server architecture Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 14
Classification of DBMSs n n n n Based on the data model used n Traditional: Relational, Network, Hierarchical. n Emerging: Object-oriented, Object-relational. Other classifications n Single-user vs. multi-user. n Centralized vs. Distributed Homogeneous DDBMS vs Heterogeneous DDBMS Federated or Multidatabase Systems Distributed Database Systems Based on cost factors Big data models : key value, document, graph, etc Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 1 - 15
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