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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Re: determining ID-ness in XML
 ># 1 is minimal-impact. Can it be sold? I.e., if you > want the "name" attr to be an ID, then you need the following > at the top of the file with a line for each element type > that "name" can appear on: > > <!DOCTYPE rootType [ > <!ATTLIST element1 name ID #IMPLIED> > <!ATTLIST element2 name ID #IMPLIED> > ... etc... > ]> > > I'm not sure it's going to be easy to get the community to > buy into this. There are a couple of technical problems with this soluion: a) Since it relies on XML 1.0 DTDs, it doesn't work properly with namespaces b) Since it requires all the declarations up front, it doesn't work well for streaming output > The namespace approach(es) have the huge advantage of making > an important semantic aspect of XML documents self- > documenting. In fact, on the Web, I might argue that the > lack of a clear self-documenting way of establishing the > semantics of '#whatever' in a URI reference is a nearly > fatal architectural flaw. I completely agree this is a serious problem. > Hm.... the one problem is that if you're dealing with XHTML > or SVG, which already *have* ID elements defined normatively > as part of the language, you have to say what happens when > there's a conflict, e.g. suppose you have > > <html:div id="p3"> ... </div> > <html:div xml:id="p3"> ... </div> The problem that xml:id is not completely solving the problem, at least as I see it. A complete solution would allow me to declare in the instance that such and such an attribute is an ID attribute, whereas xml:id only allows me to say what the ID of an element is. Just as with default attributes, I can normalize my instance to add default attributes and get rid of the DTD dependency, so with ID attributes I ought to be able to apply some normalization process that makes the ID information in the DTD (or maybe schema) explicit in the instance. Overall xml:id is pretty intrusive, especially at this stage in the development of XML: it requires all the gazillions of existing XML vocabularies that wish to take advantage of DTD-less ID's to switch from whatever attribute name they are using at the moment to xml:id. This can be mitigated to some extent by allowing both an ID attribute and an xml:id attribute simultaneously provided they have the same value. An alternative would be to have an attribute that declares the name of the attribute that is an ID attribute, say xml:idatt. To make this useable, xml:idatt would be inherited. In the typical case where all elements use the same attribute name for an ID, this means that a user has only to add something like xml:idatt="id" or xml:idatt="rdf:ID" to their root element and everything works. You would also need to allow xml:idatt="" to disable inheritance. James 
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