Inheritance in XML (was Re: Problems parsing XML)

[Paul Prescod]

Jeff Larson wrote:
> 
> Certainly there is a lot that can and should be done with XML, but I'm
> not convinced its any universal data representation panacea.

I don't think that anyone ever claimed it was (well, perhaps the press).

But that doesn't mean that the fervour is misplaced. When is the last
time you came across a technology that was an "xxx panacea" where "xxx"
can be anything? If we only got excited about panaceas, we would live in
a pretty boring industry. XML makes the job of defining new
easy-to-read, easy-to-parse, easy-to-understand languages much, much
easier. You can go out of your way to undermine those features if you
want. You can also ignore them. But on average, we will be better off,
which is something to get excited about.

> Take for example an Excel spreadsheet.  This is essentially the binary
> serialization of a complex data structure.  Assume that magically this
> becomes an XML document, what now?  You can't reason about this in any
> meaningful way without understanding the semantics of every element.
> Assuming the semantics are documented, you might be able to extract
> information from it (which makes it worth having), but it is doubtful
> that you can modify it reliably.

You can modify it reliably if the DTD/schema is complete. If not, you
guess, just as with a partially documented API.

> In theory we're now "free" to
> implement our own spreadsheet editor on top of this "open" data model,
> but is that really going to happen?  No, we'll continue to use
> the API provided by the vendor because its the implementation of the
> semantics that's the hard part.

Not in my experience. There are dozens of tools that I can download that
work with RTF, Frame MIF or PDF, and a small handful that talk to the
Word, FrameMaker or Adobe Acrobat APIs. Furthermore, the formats
described above have multiple independent implementations. The APIs do
not.

Paul Prescod  - http://itrc.uwaterloo.ca/~papresco

[Woody Allen on Hollywood in "Annie Hall"]
Annie: "It's so clean down here."
Woody: "That's because they don't throw their garbage away. They make 
        it into television shows."

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