June 2010
Intermediate to advanced
266 pages
5h 55m
English
Content preview from Patterns of Data ModelingBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 5
Item Description Template
There are two templates that involve items and their description.
- Item description. Arises when the same model relates data and metadata. The item description template frequently occurs, but is visually less striking than other templates in this book—the template involves only two entity types and one relationship. You must exercise judgment in deciding when one entity type is metadata with regard to another.
- Homomorphism. Maps between two Item Description templates and expresses an analogy. The description of item 1 is to item 1 as the description of item 2 is to item 2. The relationship between items connects occurrences. The relationship between descriptions constrains occurrences.
5.1 Item Description ...
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