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XML Schema, IAA-XML, and IFX Data Types

The W3C committee is defining a schema to be used for XML message definition and validation. One of the advantages of using the XML schema over DTDs is the ability to use and validate data types. The schema implementation is not yet available, however, forcing the first implementation of IAA-XML to use DTDs.

Oracle has examined the XML schema draft specification of data types, found at http://www.w3c.org/TR/2000/WD-xmlschema-2-20000225, and compared them with the IFX data types, as shown in Table 28.

XML schema has additional primitive data types for float (floating point number), double (double precision floating point number), TimeInstant, TimeDuration, RecurringInstant, IDREF (like IDREF in DTDs), ENTITY (like ENTITY in DTDs), and NOTATION (like NOTATION in DTDs). In addition, XML schema has derived data types that are specializations of primitive data types, such as language, integer, date, time, and name. In addition it supports user-defined data types.

Furthermore, the date and time formats for IFX, although functionally equivalent, are implemented differently. The IFX timestamp specification is the same as the XML schema format. If IAA-XML users choose to implement IFX conventions for other date and time formats in adapters, those adapters will have to change when XML schema has been adopted. Except for timestamp, IAA-XML DTDs will not use the IFX date and time data types at this time; they are defined only for consistency.