A declarative schema works well with XML data streams in a distributed context, where validation should be more functional and use a processing model that evolves beyond a single, static document for XML content.
by Kurt Cagle
January 4, 2008
lthough XML Schema was intended to be used to provide a better validation and definition layer for XML than Document Type Definitions (DTDs), certain underlying concepts were translated unintentionally. One concept was the notion that attributes could be set to enumerations (lists), but those enumerations needed to be specified within the schema itself. As XML becomes more distributed, as data structures become more complex and dependent on not just static but dynamic definitions, developers are beginning to recognize the need to have a schema language that itself supports such dynamic definitions.
Because ISO Schematron can now utilize XPath 2.0 (especially including functions such as doc() and unparsed-text()), Schematron may prove to be the critical "distributed validation" language for business content. I'll discuss Schematron in more detail later, but many issues for which Schematron seems remarkably well suited became obvious to me while doing some consultative programming for Nordstrom—the high-end clothing retailer.
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lthough XML Schema was intended to be used to provide a better validation and definition layer for XML than Document Type Definitions (DTDs), certain underlying concepts were translated unintentionally. One concept was the notion that attributes could be set to enumerations (lists), but those enumerations needed to be specified within the schema itself. As XML becomes more distributed, as data structures become more complex and dependent on not just static but dynamic definitions, developers are beginning to recognize the need to have a schema language that itself supports such dynamic definitions.
