W3C home > Mailing lists > Public > xml-uri@w3.org > May 2000

Inclusion loops

From: Robin Berjon <robin@knowscape.com>
Date: Thu, 25 May 2000 01:48:27 -0400
Message-Id: <4.1.20000525012632.00a1eb10@mail.knowscape.net>
To: xml-uri@w3.org
Hi,

I apologize if 1) the following issues have already been raised -- this
list has been pretty intense and I haven't been able to follow everything,
and the archive didn't turn out any meaningful results for my searches, and
2) this is not directly related to namespaces, it did seem germane enough
to me.

I was reading the XInclude WD when I came accross this:

3.2.1 Inclusion loops
When processing nested xinclude:include elements with parse="xml" , it is
an error to include a resource that contains an xinclude:include containing
a URI reference that has already been processed in the inclusion chain.

At first reading it made total sense. Most include (pre)processors forbid
inclusion of already included documents, for obvious reasons. However most
of these work with file system based inclusions, which is quite different.
That's why something bothered me about the above subsection, and I had to
go back to it.

On several subsequent calls, it is very possible for the same URI to
dereference to several different documents. In which case, one XInclude
might wish to include an URI already included, knowing that it will return
a different document, one that eventually won't lead to a loop.

I know it's a marginal case at best, but the confusion (one URI == one
stable resource) seems to me to be potentially dangerous.

I was turning to XSLt hoping that document() and/or generate-id() might
lead to a solution, but it seems to make the same assumption:

12.1 Multiple Source Documents
.../...
Two documents are treated as the same document if they are identified by
the same URI. The URI used for the comparison is the absolute URI into
which any relative URI was resolved and does not include any fragment
identifier. One root node is treated as the same node as another root node
if the two nodes are from the same document. Thus, the following expression
will always be true:
generate-id(document("foo.xml"))=generate-id(document("foo.xml"))

I browsed around the W3 site looking for general directives regarding URIs
and XML, but found little or none. Maybe I'm missing something, but the
potential for problems seem sufficient that this would need to be addressed.

Hoping I'm not totally off,



.Robin
Critic, n.: A person who boasts himself hard to please because nobody tries
to please him.
Received on Thursday, 25 May 2000 01:46:06 UTC

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