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External Frequency Constraints |
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By Scot Becker on
9/27/2004
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Just as internal uniqueness constraints can be generalized to internal frequency constraints, external uniqueness constraints can be generalized to external frequency constraints.
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Frequency constraints |
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By Scot Becker on
7/30/2004
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Adding a frequency constraint to a role means that once the role is populated with a given object instance, that same object instance must populate the role between some minimum and some maximum number of times.
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Join Path Subset Constraints |
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By Scot Becker on
7/1/2004
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I thought I would write up a quick post about my favorite ORM constraint. I like this one because it expresses non-trivial business rules, comes up frequently, and is mostly impossible in the (non-note) constraints supported by ER/UML.
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Entity and Value Types |
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By Scot Becker on
1/26/2004
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For people new to ORM, perhaps one of the most confusing ORM distinctions is that of entity types vs. value types. This entry is intended to describe value types, entity types, and the differences between the two as well as clear up some common misconceptions about these classifications of objects.
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More Nesting Schema Transformations |
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By Scot Becker on
10/20/2003
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Sometimes you may not always spot a fact type that is a candidate for nesting/co-referencing and will instead model it as a ternary or higher arity fact type (the relationship between these schema patterns is covered here). As you add facts, you may notice that some groupings of facts have similar patterns with their related object types.
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Unary Schema Transformations |
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By Scot Becker on
10/14/2003
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We’ll look at a more trivial transformation: transforming multiple unary facts into higher arity schema fragments.
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Adding Temporal Facts to an ORM Schema |
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By Scot Becker on
10/11/2003
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It is occasionally a system requirement to allow for the recording of history about a particular fact. Borrowing a bit from a newsgroup post I recently answered, I'd like to talk a bit about adding temporal facts to an ORM schema.
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Surrogate Keys |
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By Scot Becker on
10/3/2003
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Surrogate keys can be implemented in ORM by merely using a surrogate object and fact.
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Nested Binaries, Co-referencing, & Ternaries |
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By Scot Becker on
10/1/2003
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One of the more subtle ORM schema transformations is the relationship between ternary fact types, nested binary facts with a functional role, and co-referenced object types with a functional role.
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