Class 2 | Week 3 | DAT601

Todd's lesson today begun with a brief of him telling us that we will be finishing up on conceptual modeling today and moving onto logical design next week, consequently we should also be finishing up our conceptual phase of our practice report.

Union types is our first topic today, this describes the relationship between a single superclass/sublass with more than one other superclass.

After he showed us an extensive diagram modeling a university structure in terms of it's people I have gained a greater understanding of the topic.

The rest of the lesson is for our group to work on our conceptual model work.

Class Notes
Modeling with union types

union type or category
    represents a single superclass/subclass relationship with more than one superclass
    
    subclass represents a collection of objects that is a a subset of the UNION of distinct entity types
    
    attribute inheritance works more selectively
    
    category can be total or partial

some modelring methodologies do not have union types
    usually (always?) clearer to use specification/generalization

U = UNION (BOTH TOGETHER)

D = ONE OR THE OTHER


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