Although it had been discussed privately for months, the Model Schema Language (MSL), "an attempt to formalize some of the core idea in XML Schema," arrived publicly in an email from Jonathan Robie to xml-dev.

Reading MSL, a project of Allen Brown, Matthew Fuchs, Jonathan Robie, and Phillip Wadler, requires some understanding of mathematical notation:

"MSL is described with an inference rule notation. Originally developed by logicians, this notation is now widely used for describing type systems and semantics of programming languages. A basic understanding of grammar rules and first-order predicate logic should be adequate to understand this paper; all other notations are defined before they are used."

This formal approach allows MSL's creators to describe XML Schema in a manner which "is both concise and precise," though MSL does not provide a complete model of all of XML Schema's features.

MSL's creators note that "MSL closely resembles the type system in Xduce," an XML processing language which influenced TREX, another language for describing XML document structures.

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• Schemarama (from XML.com)
• W3C XML Schema calls for on-line feedback
• XML Schema reaches final leg of journey