Dissillusioned about interoperability.

Richard Lanyon rgl at decisionsoft.com
Fri Oct 8 17:36:54 BST 1999

On Thu, 7 Oct 1999, Simon St.Laurent wrote:
> At 05:13 PM 10/7/99 -0600, Kent Sievers wrote:

> >A tool like, say, a markup language other than XML?  One that only had one 
> >way to mark up a simple name/value pair?  That is what we left behind.

> We haven't left anything behind yet, not by a long run.  What I'm talking
> about is a tool that would let you map:
> everybody else's damn structures -> my structures

You're going to need to do this with a transformation language of some
sort - no other solution is going to be flexible enough to deal with the
variety of formats in which data is likely to appear. I don't think this
is a problem with XML, however, because I don't think specifying
structures was the problem XML set out to answer. Indeed, a system
rigorous enough to give only one layout for arbitrary data would probably
be so complex that no-one would ever use it. The main advantages are:

a) XML frees us from writing new parsers to accompany every new structure.
b) XML is sufficiently familiar to anyone who's used HTML that it might
actually catch on.

The real problem is thus that writing transformations seems so painful,
and that's really a fault with much of the current software available to
do transformations. I'd like to think that XML Script (www.xmlscript.org)
is a significant improvement in this field.

> Mike Hatalski pointed out IBM's XML Translator Generator - it's one option,
> though I'd like to see it given a prettier face.
> http://www.alphaworks.ibm.com/aw.nsf/techmain/5F60964153C4274788256776006817AA

The problem being that this is essentially a DTD-to-DTD mapper. Lots of
XML "out there" in the real world is going to be DTD-less or have very
underspecified DTDs. More importantly, you're often going to find that you
want your transformation to depend on the content/attributes of an
element, rather than the element type. This is certainly the case with
	<object type="myType">content</object>
Where you need to look at the `type' attribute to do your transformation.
This is comparatively straightforward in XML Script, where you can do
things like:
	<_if test="object.type == myType"></_if>
	<_foreach object="object{.type == myType}"></_foreach>

Richard Lanyon (Software Engineer) |     "The medium is the message"
XML Script development,            |             - Marshall McLuhan
DecisionSoft Ltd.                  |

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