[dsdl-discuss] URL (Re: Datatypes strawman)

 From: "Martin Bryan" <mtbryan@sgml.u-net.com>

> A sequence of valid resource identifiers that form a Uniform Resource Identifier (URI) as
> defined in IETF RFC 2396, as amended by IETF RFC 2732, or an Internationalized
> Resource Identifier (IRI) when this specification is formally approved as an IETF standard. > Values can be absolute or relative, and may have an optional fragment identifier.
> Constraints: fixedLength; minLength; maxLength; pattern

There is a problem with xsd:anyURI (which I named, b.t.w. in an effort to get names
that were clear) that URIs are so variable in syntax it is very difficult to do much
validation on them.

This is specially true of IRIs, which anyURI includes.

So I tend to think that URIs are not really a datatype at all.

They can be validated as
  * a string
  * a link
  * a complex value of whichever schemas the validator knows about

XML Schemas moved IDs into two parts: the datatype just tests the tokens,
while the uniqueness checking occurs outside, not as a datatyping issue.
I think you will find that for XML Schemas, the value space of a URL
is the string, not the (resolved-to-absolute) locator.

Cheers
Rick

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