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Alaric B. Snell wrote:
>...
>
> Because XML has a fragile data model, designed for publishing stuff to a
> browser rather than transfer between applications?
XML is based on SGML which was invented long before browsers as we know
them.
> ... In HTML you just ignored
> unknown tags, which was fine because the text inside would still be rendered
> just maybe without the desired styling. With XML they made everything more
> fragile, it had to conform to a DTD, but your document supplier could
> suddenly start supplying documents with a different DTD and as long as they
> XSLT pointed at by <?xml-stylesheet?> was also changed to work with the new
> DTD it'd still work OK. It's aimed more at displaying data to people than for
> interchange of information between bits of software... I'm still trying to
> find out where the 'XML data' idea first arose.
It arises naturally from the observation that structured data (tuple
structured, hieararchically structured, graph structured, recursive) is
a subset of the kinds of data you will find in the documents XML was
designed to handle. A telephone book is tuple-structured. An airplane
manual is mostly hierarchically structured but with frequent escapes to
graph structure. There is no boundary between data and documents but of
course there may be a point on the spectrum where XML produces small
benefit (e.g. if CSV is all you need). At that point you might use XML
merely to leverage the existence of XML-aware tools. If you don't need
them then you probably don't need XML.
Paul Prescod
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