RE: typing (was RE: Personal reply)

["David E. Cleary" <davec@progress.com>]

> -----Original Message-----
> From: Simon St.Laurent [mailto:simonstl@simonstl.com]
> At 02:58 PM 3/12/01 -0500, David E. Cleary wrote:
> >Because the XML instance conforms to a schema that says the value element
> >contains a decimal number.
>
> Answering "it is a decimal number because the schema says so" doesn't
> answer the question in any strong way - sorry.  That answer is predicated
> on exactly the kind of agreement I don't think we have here.

If I have a service on the Internet where I say I support messages or
documents conforming to a particular schema, then anyone who wants to send
me something has to agree that value is a decimal number. If they send me an
alphanumeric string, I will not validate it and reject it. Even without
schema's and using a DTD, my application would rightfully reject it even
though that instance is valid in regards to the DTD. As far as software that
accepts arbitrary XML markup and is able to generate usefull work from that,
I'll leave that to the acedemics. It is not something that adds any value to
my areas of interest.

> Data types are useful in an important set of use cases.  I don't believe,
> however, that data types are so important that their existence should be
> permitted to complicate use cases where data types are
> unnecessary, nor do
> I believe that they provide any fundamentally strong underpinning for
> communications.

Stick with DTDs, DOM Level 1 or 2, and SAX and you are all set. However, you
shouldn't stand in they way of those important set of use cases from taking
advantage of datatyping in XML.

> I don't object to data types as just-another-kind-of-labelling.  I
> virulently object to the notion that data types have any kind of strong
> intrinsic meaning, however, or that XML Schema should somehow be
> privileged
> because of the nature of the work (typing) that it performs.

Sorry, but since the W3C created XML, I would be surprised if XML Schema
wasn't priveledged in this regard.

> Telling me "don't use the feature if you don't like it" isn't a
> reasonable
> answer to the kinds of problems we're addressing here.

The only problem I see being addressed here is that some people don't like
XML Schema and would rather see it replaced with their own favorite schema
dialect, or nothing at all. The way to move forward is to start making the
PSVI more suitable for any schema dialect, not throwing out XML Schema. It
should be possible to take a well formed document with no schema or DTD and
generate a default PSVI that allows it to work with PSVI aware APIs. That is
much more usefull than throwing darts at the W3C or XML Schema. But then
again, you have those who argue the Infoset, let alone a PSVI, is bad for
XML.

--------------------------------------------------------------------------
David Cleary
Progress Software

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