Re: extensibility in XSchema?
Welcome to the club, Mark. At 09:47 19/06/98 -0700, Mark D. Anderson wrote: >I hesitate to ask this question because (a) I haven't been >perusing either the discussion or the specs in detail, and >(b) I don't know SGML very well, which seems to be a >prerequisite to participation. No, it isn't :-). You do have to know XML, of course - and you clearly do. I don't believe that all the current participants have a strong formal background in SGML. And I have welcomed the injection of new ideas from non-SGML people. I think the only pre-requisite is a strong familiarity with information management and ability to think hard and take time to work things out carefully. > >But I'd like some reassurance that when XSchema is done, >I will *not* ever have to parse comment structures to retrieve >metadata that the XSchema authors didn't choose to include >in a fixed repertoire of XSchema metadata declarations. This is certainly the vision that some people have. I think we'd all agree that any parsing of comment structures represented a broken model. However we are all discovering what the potential and limits of metadata are at present. Thus I think we shall find that there are problems that are very difficult and we may need other approaches. For example, XML cannot, per se, transmit behavior. > >Currently, if I want to write a tool that helps users create >new instances from a schema, I've been using xml >to declare the "template", not a dtd, because I found it so >objectionable that I would have to read dtd comments to get >the information I wanted. We sympathise. My latest DTD (VHG) has precisely this problem. But I don't want to hack my own template before XSchema is done. > >No fixed metadata will accomodate everything someone might want to know >about an element: suggestions for what GUI control to use for >entry and read-only reporting, a short and a long help text, >special validation regexps, complex conditional relationships >across elements, and so on. Agreed. I think agreement on interactive behavior is a very challenging area - if we could agree on some aspects it would be a major advance. >Right now, writing a tool for creation of new xml documents >from only a dtd for information is like trying to write a >database entry tool from only the rdbms-level schema information. >The information that a DTD provides is a joke, from the perspective >of an authoring tool. Well, I wouldn't use the word 'joke', but I agree you have to go outside the DTD. Nonetheless the DTD can be quite useful for *some* applications. > >There seems to be a constant undercurrent of religion in xml-dev >about validation vs. parsing vs. semantics, whose portent I >don't apprehend. Yes. It's healthy that there are a variety of views. This is a very difficult problem because it is the first time that behavior (I use 'semantics') is being discussed in a global - and therefore partailly unregulated - context. I think that there is a very wide spectrum of opinion, depending on where you come from. Note that for the first year a large number of the participants in XML had an SGML background. That's changing, especially on XML-DEV. Lots of people have strong formal backgrounds from other disciplines. And - in my view - that's healthy. But don't write SGML off - it is a very powerful approach with proven success. However it's not always easily accessible. >The information necessary for validation is >typically insufficient for an authoring tool. If the data >structure can't accomodate the other information which the authoring >tool needs, then it will be left with putting information in >comments, or in some completely different file. Yes. This is one of the motivations for XSchema. I should caution that XML-data and RDF also are involved in this sort of activity. Thus XSchema may need to qualify its proposal with things like: - we propose [a patter/rule language], but may later revise this to be compatible with XSL - we propose [semantic validation criteria] but may later revise these to be compatible with RDF. > >I would expect that everything necessary for validation would >be an explicit part of XSchema, but that the schema for XSchema >itself (metametadata) would allow arbitrary elements in a valid >XSchema schema. I look forward to the next draft :-) P. xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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