Planning Your Own User-Derived Data Types
- Picking Foundations The built-in primitives offer a lot of choices, but selecting among them isn't always easy. The set of facets needed to create a particular set of limitations isn't always obvious.
- Examining the Facets The XML Datatypes spec provides 'fundamental facets' (Equal, Order, Bounds, Cardinality, Numeric), as well as constraining (length, minlength, maxlength, pattern, enumeration, maxInclusive, maxExclusive, precision, scale, encoding, period).
- Limitations Once you get used to the pattern expression language and the use of facets to shape your data types, the tools are powerful. The pattern expression language is a little different from regular expressions, however. Also, there isn't any mechanism for describing the units for a particular data type - remember the Mars Lander?
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Copyright 2000 Simon St.Laurent