INFO 340 - April 21, 2004 - L08 - ER Modeling
Assignment 3 April 28th
Mid-term May 5th

Model Diagraming:
    > Have notes for your model
    > Have a title for it
    > Have a description for the model

ER Notation: Recall
    > What are Entities, Attributes & Relationships
    > Degree of relationship
    > Multiplicity of relationships
        - Cardinality
        - Participation
    > Attributes
        - Types
        - On Relationships
    > Strong and weak entity types

Fan Trap
    > Where a model represents a relationship between entity types, but the pathway between certain entity occurrences is ambiguous.

Chasm Traps
    > Where a model suggestions the existence of a relationship between entity types, but the pathway does not exist between certain entity occurrences.
    
Relationships:
    > Is-A
    > Has-A
    > Answers to - hierarchy
    > Causal

Enhances ER Modeling
    > ER works well for tradition business applications
        - Stock control; product ordering, etc...
    > ER does not work so well for complex 'object-like' systems
        - Geographic Information Systems
        - Computer-Aided Software Engineering
        - Multimedia publishing
        - Online publishing/hypertext, etc...

Specialization/Generalization

Two Kinds of Constraints
    > Participation
        - Mandatory
            * You MUST
        - Optional
            * You COULD
    > Disjoint
        - Disjoint {OR}
        - Non-Disjoint {AND}

Aggregation
    > Indicates a whole-part relationship (in addition to a binary relationship) `
    > Aggregation is conceptual

Composition
    > A specific form of aggregation that represents an association between entities, where there is a strong ownership and coincidental lifetime between the whole part