[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: What is XML For?
> > > No way. Have you ever looked at a spec for a binary file format? Most > 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 disagree. > > We're talking about the kind of people who spend most of their day in > > 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 from > 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 together > > > lurking around my systems. > > > > If it is running on YOUR SYSTEMS then it isn't deployed in the sense I > > 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 dozens > of > independent implementations and zillions of users). I wasn't there at the > beginning, but they did pretty much what I'd have done if I was (he says, > modestly). > > PNG is a nice example of a file format. It's extensible by third parties > 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 is > compressed in some bizarre new way. In which case, it is marked so that > 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 image > but > doesn't understand this chunk it should remove it since it won't be up to > date if the image is changed > > 3) Finally, the chunk should just be ignored, and left untouched if the > 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... but > 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 add > abstract style information) > > to: > > <document> > <title>Alaric's Cheese Bible</title> > <para>...</para> > </document> > > (extending that to expressing metadata, but still expressing the metadata > 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 added > 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 up > 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 than > 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 somebody > somehwere made a mental leap from "styling a human-readable document" to > "data transfer". There are gray areas between the two, since an invoice > might > well be considered to need to be both a readable document and a piece of > data, but nobody seems to be putting <?xml-stylesheet?> PIs in their XML > purchase orders, do they? > > > > email,faveFoods > > > "alaric@a...","Cheese"+"Yoghurt"+"Pizza" > > > > And what about recursive hiearchies? You can keep hacking the CSV format > > but eventually you'll reach a point of diminishing returns. > > Some might argue that XML is also being hacked to a point of diminishing > returns :-) Some might. But some might argue that most C and Perl code is ugly.
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