Data Model

Data model

Relatively simple representation, usually graphical, of complex real-world data structures

Entity

is anything about which data are to be collected and stored

Attribute

is a characteristic of an entity

Relationship

describes an association among (two or more) entities

Business Rules

Brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization’s environment

Hierarchical, Network, Relational, Entity relationship, and Object oriented

The Evolution of Data Models

GUAM (Generalized Update Access Method)

Based on the recognition that the many smaller parts would come together as components of still larger components

Information Management System (IMS)

World’s leading mainframe hierarchical database system in the 1970s and early 1980s

Hierarchical Model

Each parent can have many children, Each child has only one parent and Tree is defined by path that traces parent segments to child segments, beginning from the left

Network Model

Represent complex data relationships more effectively

Schema

Conceptual organization of entire database as viewed by the database administrator

Subschema

Defines database portion “seen” by the application programs that actually produce the desired information from data contained within the database

Data Management Language (DML)

Define data characteristics and data structure in order to manipulate the data

Schema Data Definition Language (DDL)

Enables database administrator to define schema components

Subschema DDL

Allows application programs to define database components that will be used

Relational Model

Developed by Codd (IBM) in 1970 and is considered ingenious but impractical in 1970 and conceptually simple

RDBMS

Relational Database Management System

Table (relations)

Matrix consisting of a series of row/column intersections and related to each other by sharing a common entity characteristic

Relational schema

Visual representation of relational database’s entities, attributes within those entities, and relationships between those entities

Relational Table

Stores a collection of related entities. Resembles a file

Entity Relationship Model

Widely accepted and adapted graphical tool for data modeling. Introduced by Chen in 1976