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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] What is the name of a document's "type"?
 It's a question I've frequently been asked, and I haven't been able to come up with any answer that I feel confident of. Still, I think it's a useful question to answer. In my day job, writing software for a native XML database, I get customer requests such as "list the docbook documents". If they've configured our database to know about the public ID for their local modifications to the DTD, and if they include a DOCTYPE declaration when they store the document, and if they don't do anything egregious with the internal subset, we can do that. If the customer request is "list the XSLT stylesheets" then DTD's won't do. I'll need to look at the namespace qualified root element name. If the request is "list the RDDL documents", the root element name by itself won't do. I can hope they've included a DOCTYPE declaration, or see if they've got an xhtml root element, and some elements from the RDDL namespace, and hope that there aren't any elements from some other namespaces that modify the conventional meaning of RDDL elements. I could answer all of the above requests by requiring out-of-band signalling of "type information", but that complicates interfaces and introduces the potential for inconsistancies between the instance and the metadata. Note that in the above examples, all I need to know is the answer to the question "Is this document an instance of type 'x'?" I don't need or necessarily want the document or type 'x' to automagically tell me how I should process, or validate it. I can figure that out for myself, thank-you-very-much, based on what it is I'm trying to do with it at that particular moment. What I (think I) want is a reliable, minimally intrusive mechanism to associate documents (and perhaps elements) to with some type name(s). I think the most successful solution would be one that can give the most specific answer to 1) "what is this thing's type name" and accurately answer 2) "is this thing an instance of the type named 'x'?" while having the least to say about what types "mean" or imposing any particular processing model or information set rewriting. While architectural forms appear to do a good job of answering the two questions, I'm having trouble with the special lenses one needs to see the instances. Hoping to learn, Bill 
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