Overview

As previously noted, W3C XML Schemas (W3C Recommendation, May 2001) provide a rigorous and highly standardized method for describing strongly typed data. Syntactically, this is accomplished through the use of data types and data type facets. W3C XML Schemas also provide the ability to define custom data types as extensions and derivations of supported types. As one example, rather than defining numerous monetary amount data elements with different formats, the data architect can define a set of standard monetary data types that could then be applied as necessary to referencing XML elements and attributes. As the use of XML transactions to exchange, share, and move data among enterprise systems grows, this technique also acts as a method to proliferate and enforce data standards.

The application of a schema data type is actually a form of edit checking. When an XML document references a corresponding W3C XML Schema and that schema has applied data types to element and attribute definitions, the parser validation process will compare the data values contained by those elements and attributes to the data types defined in the schema. If the data values do not conform to the constraints of the data types defined in the W3C XML Schema, an error will be raised to the processing application. It is important to note that the parser will not apply corrections or modifications to the data contained in the XML document. Rather, resolution and action are left to the processing application. As an example, if the data...