Re: [unrev-II] Architectural Snag - Validation

From: Paul Fernhout (
Date: Mon Oct 30 2000 - 10:52:55 PST

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    This is an interesting observation. You are saying that the techniques
    for XML validation could be applied to other things with a hierarchical
    format. (In Kent's ROSE system defined in data and reality this is
    linked to "executables"). So, one could in effect say that "schemas"
    apply to some part of an information network to enforce a certain

    Difficulties (not necessarily objections) I have with implementing this
    approach are:
    * XML is mainly designed (and planned) for hierarchical data. While you
    can do non-hierachical data (webs) by various abstractions, it seems to
    me from a limited understanding that XML techniques (XSLT) isn't
    necessarily designed to do this better than regular coding. (Anyone,
    feel free to point to good examples of XML use for webs...)
    * DTDs and Schemas are useful, but I believe they may not express all
    the possible ways of organizing even hierarchical data. I think there
    are (with DTDs at least) some specific issues with artificial limits of
    what type of repetitive groups one can have in what area of an XML
    document. Contrast this with for example encoding XML data as Lisp
    S-expressions and instead of DTDs or Schemas providing Lisp programs to
    do validation on the expressions. That would be a fully general
    solution. However, a Schema is easier perhaps for a general editor to
    interact with for giving proper editing advice than an ad-hoc Lisp
    program. (Of course, the Lisp programs might be written mainly in a
    standard form -- approaching something like the XML Schema format but
    with extensions.)
    * (Deeper) XML (and for example RDF) makes it difficult (or impossible)
    to reference links within a documents. (Yes, there are XPointers, etc.
    but I am not yet convinced of their generality for what I mean). By
    contrast, by design, everything in the Pointrel Data Repository System
    is intended to be linkable. That is -- any relation itself can be linked
    to and in effect commented on. This is a completely extensible system.
    With an XML Schema or DTD it would not be clear how these commentary
    links would be effected or limited. One might be able to work around
    this by enforcing a DTD or Schema only on certain links which were
    linked into a specific validation space (by other links). So, your
    suggestion is inspiring some more thought on this...

    In any event, I like your suggestion. Just trying to think through what
    it means or how to make it implementable. I've been thinking some myself
    lately on how to use some XML concepts in relation to the Pointrel
    system (not validation though -- just mainly import/export), based on
    issues of technology and familiarity. If there was an XML interface to
    some parts of the Pointrel system then it would provide a well
    understood API for many common operations and an on-ramp for people who
    understood that technology (as you outline). Your suggestion paints a
    bigger picture for meaningful integration.

    I'm always torn on this issue. On the one hand, I don't want to impose
    any specific "eternal" validation limits to a set of relations. On the
    other hand, unless the relations are structured in some way relative to
    code intended to search or otherwise process them, the information will
    be difficult or impossible to use.

    -Paul Fernhout
    Kurtz-Fernhout Software
    Developers of custom software and educational simulations
    Creators of the Garden with Insight(TM) garden simulator wrote:
    > Hi Paul,
    > The best idea is to validate a single file or the entire structure in
    > real time or just whenever you want or need to against an appropriate
    > schema using an available open validating parser. If the information is
    > canonical XML and the schema accurately describes what the structure and
    > data types should be, then it is suddenly a lot easier.
    > Scripting solutions, either experimental, temporary, or 'permanent' also
    > becomes a lot more fun if you can use an interface to the information as
    > expressed by the XML DOM and its relations.
    > Best Regards,
    > Joe
    > "Proprietary solutions commit the business to a legacy system."
    > FC, HP

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