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From: "Eric van der Vlist" <vdv@d...> > Even if sometimes I'd wish they are only this, I think that it's quite > limitative to restrict schemata (either syntaxic or semantic) to a set > of constraints. There are two effects: schemas viewed by their proximate effect of producing some transformed data (which in turn conforms to some other meta-schema), and schemas viewed by their ultimate effect of constraining the direct data. In other words, a schema language is expressed in terms of ultimate constraints a schema implementation actually converts the schema into a transformation functions which transforms the instance into some proximate form a schema assessor/valdator checks whether this transformation matches the allowed proximate form the report mechanism gives appropriate messages, in terms of the ultimate constraints. So, to some extent, schemas as a "set of constraints" hides "schemas as high-level transformation languages" and "schemas as high-level diagnostics generating systems." So how can we test schema implementation conformance? It seems to me that we have to have provide a conformance-meta-schema for the proximate form. Cheers Rick Jelliffe
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