[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: xsi:type and broken contracts
Paul Prescod <paul@p...> writes: > "Henry S. Thompson" wrote: > > > >... > > Um, no, the content model for dl in XHTML is (dt|dd)*, which will > > cover what your rules produce, and what they produce will look OK > > too. > > Let's not get hung up on the details of XHTML. There are many content > models of the form (x,y)+ out there. And anyhow, I can come up with > these examples all day. Well, yes and no. The reason the dt/dd example is interesting is precisely that it's an open question whether the behaviour of the original stylesheet with the new document is correct or incorrect. If you want to be conservative, the W3C XML Schema REC lets you be conservative, by 'block'ing the use of xsi:type and enforcing the use of _your_ schema, not anyone elses (see the other thread running at the moment). If you want to be liberal, and allow people to use your stuff with documents which include extensions, your stuff will always do what it should with the original material, and may or may not do anything interesting with the additional bits. I guess that's a better way of saying what I was trying to say before -- as long as you only rely on required bits, and don't work back from the end in your expressions, your stylesheets and other applications will always do the same thing with the unextended parts of instances which exploit xsi:type to extend or restrict their inputs as they would have without the extensions. What happens to the extensions themselves is anybody's guess. Just as no-one would allow a mission-critical system involving validation to do so against a client-supplied DTD (despite the fact that, as you point out in your companion message, XML 1.0 _requires_ it to do so to be a conformant validating parser), but would instead use their own, just so anyone writing a mission-critical application involving schema-validity assessment will do so against their own schema and either write it to 'block' the use xsi:type wrt extension, or ignore any other schema hints, so any attempt to use foreign types will fail (both of these strategies _are_ allowed by W3C XML Schema). Horses for courses, take your pick. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2002, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@c... URL: http://www.ltg.ed.ac.uk/~ht/ [mail really from me _always_ has this .sig -- mail without it is forged spam]
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