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   RE: [xml-dev] What is XML For?

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> > > No way. Have you ever looked at a spec for a binary file format?
> of
> > > the ones I've deal with have taken a few hours to bang out an
> > > implementation of (except TIFF; implementations of TIFF are never
> > > finished...)
> >
> > For you and me, yes. For the average business programmer? I
> > We're talking about the kind of people who spend most of their day
> > Visual Basic.
> But THEY don't even want XML; they probably don't find wandering a DOM
> tree
> any more friendly than calling whatever passes for Perl's "pack" and
> "unpack"
> in VB. They are the people who want to just have magic serialisation
> data structures to strings of bytes.

Good point. There are products (like J2EE 1.4 from what I hear) that
provide OO serialization to/from XML for "free" though.

> > > No it's not... I've got quite a few custom protocols I put
> > > lurking around my systems.
> >
> > If it is running on YOUR SYSTEMS then it isn't deployed in the sense
> > mean. I'm asking have you ever tried to deploy a protocol that would
> > have dozens of independent implementations and thousands of users?
> > That's _really hard_ and many good protocols never make the leap.
> That's purely a problem of adoption in the protocol marketplace, not
> difficulty of development.
> But I'm a little WG right now developing a protocol to replace IMAP,
and I
> helped out a bit in developing the PNG image file format (which has
> of
> independent implementations and zillions of users). I wasn't there at
> beginning, but they did pretty much what I'd have done if I was (he
> modestly).
> PNG is a nice example of a file format. It's extensible by third
> to
> create their own specialist metadata that can just be ignored by
> applications
> that don't understand it. Better than XML, those extra chunks (sort of
> like
> tags) can be marked with metadata about how applications that don't
> understand them should handle them.
> 1) The chunk might be something like an indication that the image data
> compressed in some bizarre new way. In which case, it is marked so
> applications that don't understand it are forced to reject the file.
> 2) If not, the chunk still might be something like a thumbnail image
or a
> histogram of colours used in the image; if a processor changes the
> but
> doesn't understand this chunk it should remove it since it won't be up
> date if the image is changed
> 3) Finally, the chunk should just be ignored, and left untouched if
> image
> is altered. Stuff like copyright notices and so on.

That sounds like a rather wise thing to do. Any idea why the XML spec
doesn't include mechanisms for meta-model information?

> Just to reverse positions, I see XML as useful for marking up text...
> it's not well fitted for data. As far as I can tell there's been a
> conceptual
> bleed from:
> This is <emphasis>tasty</emphasis> cheese
> (taking a string of text then slipping a few tags in here and there to
> abstract style information)
> to:
> <document>
>   <title>Alaric's Cheese Bible</title>
>   <para>...</para>
> </document>
> (extending that to expressing metadata, but still expressing the
> in
> terms of abstract styles; remove all the tags and you get:
> Alaric's Cheese Bible
> ...paragraphs...
> <title> is really just an abstract style with a schema constraint
> that
> you can only have one, and as the first thing in a document).
> to:
> <cheese>
>   <name>Cheddar</name>
>   <colour>Yellowish</colour>
>   <price currency="UKP" unit="kg">2.50</price>
> </cheese>
> ...without enough stopping to think if it's a good idea.
> I'm not even sure if the latter was what the W3C intended when coming
> with
> XML; the introduction at http://www.w3c.org/XML/ states that it was
> designed
> for publishing, not data transfer, but it's becoming used for data
> transfer
> anyway.
> Is this just people noticing that something should be used for more
> it
> was intended for (which I'm suspicious enough of :-), or is it people
> misapplying something out of foolish over optimism?
> Whose idea *was* it to use XML for data interchange? The W3C seems to
> disavow
> responsibility in the first paragraph of that introduction. But
> somehwere made a mental leap from "styling a human-readable document"
> "data transfer". There are gray areas between the two, since an
> might
> well be considered to need to be both a readable document and a piece
> data, but nobody seems to be putting <?xml-stylesheet?> PIs in their
> purchase orders, do they?
> > > email,faveFoods
> > > "alaric@alaric-snell.com","Cheese"+"Yoghurt"+"Pizza"
> >
> > And what about recursive hiearchies? You can keep hacking the CSV
> > but eventually you'll reach a point of diminishing returns.
> Some might argue that XML is also being hacked to a point of
> returns :-)

Some might. But some might argue that most C and Perl code is ugly.


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