Chapter 2 Database Environment

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

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

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

Mapping External/conceptual mapping Conceptual/internal mapping Example

Data Independence Logical data independence Physical data independence

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

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)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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