|2002年11月16日||RULES FOR (R) [ RESOURCE-EVENT ]||BACK >> 目次|
● Rules for replication (R) of identifier (with T-formed ERD)
The followings are the possible logical combinations between two entities, a and b:
□ (R) in the combination between "resource and event"
RULE: The identifier of the resource shall be replicated into the event.
"aRb" says that "a" stands to "b" in the relation "R", provided mathematically a description of R(a, b)
We use "aRb" not in "relation (function)", but in relationship. Both of a and b, therefore, are "resources" and R is an "event" when viewed in perspective of "Entity and Relationship" diagram, i.e.,
If and when viewed in perspective of "T-formed ERD", an entity has the identifier of code (or number)--so, "order (in the form of 'verb')" is an entity because it has order-NO.
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