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

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

> Not sure whether your mixing two different thing here. IDs and URLs are both
> subsets of strings, with different character set constraints. ID uniqueness
> checking, like URL resolvability, is outside of datatyping. ID uniqueness
> checks fall within Part 2's responsibility. But where does the checking of a
> namespace URL against the IETF rules come in? This is why I wanted to
> introduce a primitive datatypes for URLs and their replacements, to allow a
> level of checking for things where URLs are required.

Without a built-in knowledge of the URL scheme, you cannot say that
   http://www.eg.com/x/../x
is the same as
   http://www.eg.com/x

That is what I meant by the value space of XML Schema URLs being
strings not locators.

From memory, we found it very difficult actually to check against the
IETF rules, because once IRIs are allowed, almost any character
can appear.

The current practise of URLs is that the ASCII form given by the
RFCs is what is used for binary protocols, but that documents and
software should use IRIs, in which you can have the direct characters.
The IRI RFC has been very slow coming, but it is certainly the
intent of the W3C I18n WG and the IETF people involved to
use IRIs more.

Cheers
Rick

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