1. Chapter 2 Database Environment

2. Agenda Three-Level ANSI-SPARC Architecture Database Languages Data Models Functions of DBMS Components of DBMS Data Dictionary & Information Resource Dictionary System

3. Three-Level ANSI-SPARC Architecture External –User's view Conceptual –Organization view –Constraints, security, & integrity Internal –Physical presentation –Storage, security, & encryption

4. Database Schemas Database schema (intension) & database instance (extension) External schemas (subschema) Conceptual schema Internal schema

5. Mapping External/conceptual mapping Conceptual/internal mapping Example

6. Data Independence Logical data independence Physical data independence

7. Database Languages Data Definition Language (DDL) –Structured Query Language (SQL) Data Manipulation Language (DML) –Procedural DML –Non-procedural DML Structured Query Language (SQL) Query-by-Example (QBE) Fourth-Generation Language –Form, report, graphics, & application generators

8. Data Models Definition –Integrated concept for describing data, relationship and constraints Types –Object-based data models –Record-based data models –Physical data models (internal structure, ordering, & paths)

9. Object-Based Data Models Entity-relationship –Entity, attribute, relationship –Usage Object-oriented –Object, class, subclass, inheritance, state (attributes), behavior (methods or actions), encapsulation, message, polymorphism –Usage

10. Record-Based Data Models Relational data model Network model Hierarchical Model

11. Relational Data Model Terminology –Relations –Attributes –Tuples Record relationship –One-to-many relationship Usage –Ad hoc reporting Example

12. Network Model CODASYL DBTG Integrated Date Store (IDS) Terminology –Data item & group item –Record type (owner, member) –Set type: optional, mandatory, permanent –Schema & sub-schema

13. Network Model Set –Owner & member –Singular or system –Pointer chains (single-linked, doubly linked, member-to-owner) Record relationship –Many-to-many relationship Usage –Large volume transaction processing

14. Network Model Schema DDL –Schema description –Area description –Record Description –Set description Data Manipulation Language (DML) –Host language –Sub-schema DDL

15. Hierarchical Model IBM Information Management Systems Terminology –Tree, general tree, & subtree –Nodes, root node, child nodes –Segment type Record relationship –One-to-many relationship –Excellent referential integrity –Inflexible –No many-to-many relationship

16. Hierarchical Model Hierarchical record structure (pointer or address) –Level of tree (significant - insignificant) –Pre-order traversal or top down –Post-order traversal or bottom up –Twin pointers, forward links, backward links, logical pointers Usage –Large volume transaction processing

17. Functions of a DBMS Data storage, retrieval and update A user-accessible catalog Transaction support Concurrency control Recovery Authorization Integrity Data independence Data communication Other Utilities

18. Components of a DBMS Query processor Database manager File manager DML preprocessor DDL compiler Catalog manager

19. Components of Database Manager Authorization control Command processor Integrity checker Query optimizer Transaction manager Scheduler Recovery manager Buffer manager

20. SYSTEM CATALOGS Definition –Data dictionary –Information about database Types –Active –Passive –Integrated –Standalone

21. Information Resource Dictionary System (IRDS) IRDS standards by ISO A set of rules to store and access information in the data dictionary Objectives: data extensibility, data integrity, & data access control Service interface works with: panel, command language, export/import files, & application programs

22. Points to Remember Three-Level ANSI-SPARC Architecture Database Languages Data Models Functions of DBMS Components of DBMS Data Dictionary & Information Resource Dictionary System

23. Assignment Review chapter 1-2, appendix c Read chapter 3 & 4 (skip relational calculus 4.2)