Datatypes

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?