[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: using namespaces to version
Hi folks, First of all, thanks to everyone who's participated in this thread so far. If I can direct attention back to my original problem. For my particular project (CellML - http://www.cellml.org/ , if anyone's interested), the versioning process will almost definitely affect the validity of documents (i.e., if there was a schema, it would change), and the expected behaviour of processing applications. Backwards compatibility is likely to be on an element-by-element basis. For instance, the content model and semantics of the <connection> element will probably not change in the near future, but the <variable> element almost definitely will be extended (although the CellML 1.0 way of doing things will probably not be made invalid). Because this element affects the definition of a mathematical model, it is highly unlikely that a CellML 1.0 processor will be able to process the extended form of the CellML 2.0 <variable> element in a manner conformant to the CellML 2.0 specification. Some of the validity constraints on CellML are currently too complex to be expressed using DTDs or schema (AFAIK). Instead we have a technical specification which describes the validity constraints and semantics for all of the elements (similar to MathML's specification). For these reasons, I expect the namespace URI will point to human-readable documentation instead of a schema or RDDL document. Other than the XPath problem that David Carlisle raised (which is easily solved), I can still not see any good *technical* reasons why I shouldn't use namespaces for versioning. In fact, it's quite attractive because CellML is likely to be available and processed in fragments, in which there won't use a DOCTYPE declaration, and I don't want to define some kind of version attribute on every language element. Comments, anyone? -- Warren Hedley
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