At 14:09 1999 07 13 +0900, MURATA Makoto wrote:
Having finished my summary, I have one question for clarification. Did the
XML Linking WG want to use XPointer only when the media type is text/xml or
application/xml? Or, did they want to use XPointer for other xml-based
media
types, but give up simply because the current media type mechanism cannot
specify "This is of the media type "model/foo" which is based on XML"?
If the resource is XML, the fragment identifier is to be interpreted
as an XPointer.
The inverse (and converse, it therefore follows) of that statement is
neither necessarily true nor false. The XLink WG does not want to prevent
XPointer from being used in non-XML resources, but it also does not want
to say anything one way or the other because that is outside the scope
of the XLink WG.
Asks Rick Jelliffe:
I am confused about a related question: I have heard somewhere that the
XPointer
group was going to make XPointers only valid for pointing into XML
documents.
So, for example, it would not be legitimate for an XPointer to point into a
WebCGM
document or other structured data. Is this true?
No.
Also, there seems to be paradigm difference between the conventional idea
of a URL (which fetches some resource) and an XPointer (which points to some
span in some resource but doesn't necessarily return anything).
XPointer doesn't necessarily point to a span. It addresses things
(where things might be many of the objects in an XML tree or possibly
a "span" of such objects).
I had a bit
of
difficulty with this at first, and I suspect that others with HTML
expectations will
be the same. Murata-san's question relates to this too: does an XLink
always
return a resource.
"Return" is a semantic, and XLink's semantics are not finalized.
I don't really know how else to answer your question, as it doesn't
really make sense to me. XPointer addresses, and XLink (which may
use XPointer) links addressed things. What is means to link addressed
things is yet a different question.
If XPointers can only be used with XLinks,
That is not true.
does that mean
that
XPointers always return a resource too?
XPointer never return anything. They address things.
If the resource returned is
different from
a type attribute, is it always an error?
This question isn't answerable as it depends on erroneous assumptions.
Shane P. McCarron says:
However, it might also be useful to import other things - like plain
text. XPointer/XLink needs to work for this as well. I don't see how
we can limit the scope of the target.
XLink should be usable with any addressing mechanism, not just XPointer.
XPointer might be usable to address into non-XML resources, but it is
not up to the XLink WG (or the XPointer spec) to address [pardon the pun]
that issue, so you will not see either XLink or XPointer talk about how
to link into plain text. How a fragment identifier of a URI-reference
addresses into plain text is up to the "plain text mime type" to decide.
Once that's determined, XLink will automatically work with it (you'd just
give a URI-reference as the value of the locator attribute of the XLink
element).
paul