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Database Modeling with Microsoft® Visio for Enterprise Architects
book

Database Modeling with Microsoft® Visio for Enterprise Architects

by Terry Halpin, Ken Evans, Pat Hallock, Bill Maclean
September 2003
Intermediate to advanced content levelIntermediate to advanced
425 pages
16h 30m
English
Morgan Kaufmann
Content preview from Database Modeling with Microsoft® Visio for Enterprise Architects
4.1 Object Types
As discussed in the previous chapter, an ORM object type is either a value type or an
entity type. A value corresponds to an entry in a table, and is typically a character string
or numeric constant (e.g., “Ireland,” 56). A value identifies or refers to itself, so there
is no need to specify a reference scheme (identification scheme) for it.
An entity is identified by means of a reference scheme that uses one or more values.
A simple reference scheme uses only one value (e.g., the Country with CountryCode
‘US’). A good rule of thumb is “If you can write it down, it’s a value.” Clearly, you can
write down the code ‘US,’ but you can’t ...
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Publisher Resources

ISBN: 9781558609198