W3C home > Mailing lists > Public > uri@w3.org > February 2002

Re: [Fwd: Re: [xml-dev] creating a URI class]

From: Ted Hardie <hardie@oakthorn.com>
Date: Wed, 20 Feb 2002 09:23:32 -0800 (PST)
Message-Id: <200202201723.JAA32497@geode.he.net>
To: connolly@w3.org (Dan Connolly)
Cc: hardie@oakthorn.com, simonstl@simonstl.com (Simon St.Laurent), uri@w3.org, elharo@metalab.unc.edu, mnot@mnot.net (Mark Nottingham)
Me writing:
> > This seems to contradict to RFC 2396, sections 2.1 and 3.
> > 3, in particular, says:
> > 
> >    The URI syntax does not require that the scheme-specific-part have
> >    any general structure or set of semantics which is common among all
> >    URI.  
> > 
> > I read that to mean that http://www.bar.org/ and http://www.BAR.org/
> > may be equivalent where file://123abcdef and file://123ABCDEF might
> > not be, and that a reference to the definition of the http and file
> > URI schemes would be required to determine which semantics need be
> > applied.

Dan writing:
> But that doesn't mean that http://www.bar.org/
> and http://www.BAR.org/ are the same URI.
> 
> > In other words, the URI spec seems to say that semantic equivalence is
> > scheme specific and string comparison alone is not enough.
> 
> string comparison is enough to tell if two URIs are the same
> URI.
> 

Dan,
	The XML namespace doc (http://www.w3.org/TR/REC-xml-names/)
cites the same RFC I did above for URI reference.  It further
says:

  URI references which identify namespaces are considered identical
  when they are exactly the same character-for-character. Note that URI
  references which are not identical in this sense may in fact be
  functionally equivalent. Examples include URI references which differ
  only in case...

"identical" in the original is rendered in bold with <b></b> tags.  I
asssume that your statement above is that character equivalence
determines whether two items meet this test (Are they "identical"?).
This seems, however, to be the wrong test for this context.  Actually
it would be more accurate to say it would be only the first test.
After determining whether two URIs meet that test an application would
still need to check whether the two URIs are semantically equivalent
before processing.  To give a non-scheme specific example, note that
RFC2141 specifies that the leading urn of a URN declaration is case
insensitive and that urn:<nid>:<nss> and URN:<nid>:<nss> are
equivalent.
				regards,
					Ted Hardie
Received on Wednesday, 20 February 2002 12:23:36 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:25:04 UTC