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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XSchema Spec Section 2.2, Draft 1
 On Wed, 10 Jun 1998, Simon St.Laurent wrote: > Element declarations in XSchemas are made using the XSC:ElementDecl element > and its contents: We need to align this terminology with XML. We certainly are NOT declaring individual elements!. One way to fix this up would be to call these "Element Type Declarations". But philosophically, you have to ask yourself: "Are we really declaring element types?" This would be more right than what we have, but still not quite right, in my book. The word "type" implies a "type system", which we are probably not interested in. And the word "declaration" implies that this is the one and only place that the element type is "declared". That made sense in DTD-land, but in schema land, I think the terminology is a little out of whack. In my mind, the element type exists long before the XSchema processor sees it. And if a document has no XSchema the element types still conceptually exist. I suggest "element constraint declaration" and "attribute constraint declaration" with the GIs XSC:Element and XSC:Attribute. That implies that this is the one and only one declaration of this particular constraint -- which is a tautology. > <!ELEMENT XSC:ElementDecl (XSC:Doc?, (XSC:Ref | XSC:Choice | XSC:Seq | > XSC:Empty | XSC:Any | XSC:PCData | XSC:Mixed), XSC:AttDef*)> > <!-- id is the element name --> > <!ATTLIST XSC:ElementDecl XSC:id ID #REQUIRED > I don't have time to go into this in detail, but I would urge you to consider aligning the handling of content models with regular expression theory. For instance, consider allowing XSC:Any *anywhere* in a content model. This will go a long way towards the flexibility that people need when they ask for "inheritance." Because of the festering hole that is XML whitespace (if there is a clean solution, I don't know it), the situation with XSC:Mixed and XSC:Pcdata is more complicated. Will XSchema's be used to guide the ignoring of whitespace? If so, we should be constrained to the simple models XML allows. If not, we could mix in XSC:Pcdata and XSC:Mixed anywhere, as SGML does. I think that we should go for it: make the whole thing simple, orthogonal and consistent. This is an experimental language, right? If we can't try out potential over-simplifications here, then when can we try them out? > The XSC:id attribute identifies the name of the element, and is required. I don't think that ID/IDREF is going to be powerful enough for us, unfortunately. We will want to be allowed to reuse the same name for and element and an attribute, for instance. So the name need only be unique across a particular type. XML doesn't support this well, but a "linking schema" language could (in the future) or some future version of XSchema could support it directly. Michael Sperberg-McQueen described a nice syntax for describing these kinds of constraints once. I propose: XSC:name NAME -> required and must be unique among element constraint declarations. XSC:longname CDATA -> for use in XML editors, viewers and other places where a longer name might be appropriate. (e.g. never referenced, always just used for output) Paul Prescod xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...) 
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