[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: ANN: xpath1() scheme for XPointer
At 5:09 PM -0600 10/26/02, Uche Ogbuji wrote: >Wow. Too bad for content negotiation that in your world differing >representations MUST have differing URIs. Too bad for you that the real world >is much more complex. Mostly I've stayed out of the whole resource/representation debates because it's not totally clear to me why anybody cares about this, or exactly what the relevant definitions are to discuss this. Part of the problem seems to be disagreements over just what a resource is. In this context, though, I've been mulling this one or over for a day or so, and I think I can defend the position that multiple URIs really are called for here, at least by some of the definitions that are out there for URI. First of all, an XIncluded document is not just a different format. A GIF and a JPEG image formed from the same digital camera screen shot without significant editing containing basically the same information. That's why content negotiation might be appropriate in that case, or similar. That's why they may have the same URIs, because they are the same thing. With XInclude however, we have two very different documents before and after the include: <html xmlns:xi="http://www.w3.org/2001/XInclude"> <body> <xi:include parse="text" href="http://www.example.com/" /> </body> <html> This is not the same information as contained in the document after the include. I don't believe that they're just different representations of the same thing. Indeed, with fallbacks, processing the same document from different locations may produce radically different results. For example, consider a doctor's PDA that's used to query a local database to find out if a patient should be medicated: <medicate> <xi:include parse="text" href="http://www.hospital.com?patient=89765"> <xi:fallback> <1-- First do no harm.--> No </xi:fallback> </xi:include> </medicate> Furthermore, consider the most tautological definition of a resource: it's what a URI identifies. The pre-include document has a single URI. Therefore it's one resource. The post-include document has multiple base URIs according to the Infoset that XML is based on. Therefore it's several resources, not just one. Indeed since there is no one URI that points to the post include document, it's questionable whether it's a resource at all. (This is one of the things I really don't like about the tautological definition of a resource. To my mind, the post-include document is a resource whether it's got a URI or not.) But bottom line: it sure feels to me that there are different resources pre- and post-include. They are not just different representations of the same thing. -- +-----------------------+------------------------+-------------------+ | Elliotte Rusty Harold | elharo@m... | Writer/Programmer | +-----------------------+------------------------+-------------------+ | XML in a Nutshell, 2nd Edition (O'Reilly, 2002) | | http://www.cafeconleche.org/books/xian2/ | | http://www.amazon.com/exec/obidos/ISBN%3D0596002920/cafeaulaitA/ | +----------------------------------+---------------------------------+ | Read Cafe au Lait for Java News: http://www.cafeaulait.org/ | | Read Cafe con Leche for XML News: http://www.cafeconleche.org/ | +----------------------------------+---------------------------------+
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