20 lines
1.9 KiB
Plaintext
20 lines
1.9 KiB
Plaintext
%META:TOPICINFO{author="GarryJolleyRogers" date="1259118882" format="1.1" version="1.4"}%
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%META:TOPICPARENT{name="BDI.SDD_.SchemaDiscussion"}%
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---+!! %TOPIC%
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Many UBIF features are controlled through [[EnumeratedValues][enumerated values]] (i.e. a controlled vocabulary).
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Enumerated values are used in two cases:
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1 To create a main/subclass hierarchy. Example: all Representation/Label elements are structurally identical, but we desire to further specify detailed semantics of labels. For this purpose, the Label element has a role attribute, with controlled values like Full, Short, Abbrev, Sort for the default full label, short and abbreviated equivalents, and a label preferred for sorting purposes. Note that although the use of role is related to value-based weak typing, in the context used in UBIF it is used only when the subclass have identical syntax and structure to the superclasses.
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2 To express machine-readable semantics for application interoperability. Example: Applications need to know what the status value for missing data is, or which statistical measure has been used.
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In version 1.0 and 1.1 of UBIF (and BDI.SDD_) we use fully constrained schema enumerations. It is not possible to add further values. However, this is intended to be a preliminary restriction to ensure that a community consensus about relevant is reached. Ultimately, these values should be extensible through URIs.
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TEI defines [[http://www.tei-c.org/P4X/ref-VALLIST.html][three kinds of value lists]]:
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* closed = only the values specified are permitted.
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* semi = all the values specified should be supported, but other values are legal and software should have appropriate fallback processing for them.
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* open the values specified are sample values only.
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In future versions we intend to make most, or perhaps all enumerations of the kind "semi". Applications builders are asked to write their code in consideration of this.
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-- Main.GregorHagedorn - 10 May 2006 |