Weak Entity Sets:Keys, Subclasses

Table of Contents

Weak Entity Sets:Keys, Subclasses

More Design Issues

Roles

Roles Example

Roles Example

Roles (II)

Roles (III)

Roles in ODL

Roles in ODL (II)

Subclasses

ODL Subclasses

E/R Subclasses

E/R Subclasses (II)

Difference in Subclass Viewpoints

Subclass (II)

Multiple Inheritance

Problems

Keys

Keys Example

Keys in ODL

Example:

A Multiattribute Key

A Multiattribute Key (II)

Weak Entity Sets

Weak Entity Sets (II)

Weak Entity Sets (III)

Weak Entity Sets (IV)

Weak Entity Sets (II)

Example: Logins

Example: Logins (II)

Example: Logins (III)

Example: Chain of “Weakness”

Example: Chain of “Weakness” (II)

All “Connecting” Entity Sets Are Weak

All “Connecting” Entity Sets Are Weak

Email: burt@umbc

Home Page: www.cs.umbc.edu/~burt