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On Fri, 2003-10-10 at 17:49, Jonathan Robie wrote:
> Eric and Dare are both right here, depending on your perspective.
>
> As I understand Eric, he wants to use the data types of the programming
> language he uses or of the databases in which data is stored. Because these
> systems already have well-defined types, any mismatch between their types
> and the types of XML Schema get in the way.
Not only those of the programming languages, but those that need to be
supported by the applications.
We have requests to support things such as the Japanese calendar or
complex numbers in DSDL and I think we'd better find a way to let people
define what they need rather than attempting to be "universal" and
define all the possible datatypes.
> As I understand Dare, he wants to be able to do "Native XML Programming",
> using systems base directly on the built-in types of XML Schema. Most
> databases and programming languages have a set of built-in types, and many
> optimizations are based on knowledge of these types.
>
> Actually, this is one of the real advantages of the facets approach taken
> by XML Schema. You can define new types based on existing ones - if you
> need an integer that can only be a certain size, you use facets to express
> that. Any system that can handle the more general type can also handle the
> specific one. But what if you want to specify new types that are not
> derived from existing ones?
Yes, that's the issue.
>
> Many databases allow new types to be created with 'data blades' or
> 'extenders' or whatever. As Dare points out, this requires specification of
> the operations on these types - how do you compare two instances? how do
> you serialize an instance? how do you construct an instance from a
> serialized format? I'm not convinced that MathML is the right language for
> doing this, but such a language could be devised.
I am not sure either, but that's the closest that comes to mind.
> However, the problem
> turtles. The specification of these operations needs to be done in terms of
> SOMETHING, which brings us back to the set of types known in the language
> used for specifying the operations.
Yes, but this could be done through possibly complex algorithms and by
projection (a complex number could be decomposed on their real and
imaginary components).
> So what advantage would that have over doing it directly in W3C XML Schema?
What if people want to define facets on a Japanese date or a complex
number (I mean facets that knows about the operations on these types and
operate on their value space, not only pattern facets which operate on
their lexical space)?
Eric
>
> Jonathan
--
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http://www.xml.com/pub/au/74
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------------------------------------------------------------------------
Eric van der Vlist http://xmlfr.org http://dyomedea.com
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema
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