[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XSchema Spec Section 2.4, Draft 2
John Cowan wrote: > > Chris Maden wrote: > =[Snip]= > > > <XSC:AttDef Name="one-of-these" Type="IDRef" Required="Yes" > > Enumeration="index biblio gloss"/> > > > > You can't do that with DTDs. The value for one-of-these must be > > specified, and it must be a legitimate IDREF, but it is constrained to > > one of the specific IDs listed. > > Forgive me, but I find this particular instance incomprehensible. > Why would you want to refer to only one of a specific set of IDs? > Is this the SGML v. DP culture gap in action? I spend my days building GUI screens to constrain input to hard-coded sets of IDs (radio buttons) or variable sets of IDs (combo-box, list box), partly so that I can guarantee the input will fit into databases which, in turn, compete for business on the power of their referential integrity support. This is key DP usability we're discussing here - in fact my reaction was "hey, there's a nice comprehensible example!" Admittedly I would have fleshed it out a bit - <XSC:AttDef Name="OrderNo" Type="IDRef" Required="Yes" Enumeration="Order00234 Order00235 Order00237"/> <XSC:AttDef Name="PartNo" Type="IDRef" Required="Yes" Enumeration="Widget Sprogget Fluggit"/> I'm still no expert on XML, but am I right in thinking that using only DTDs there would be no way of declaring that OrderNo may be "Order00234" but may not be "Widget", while PartNo may be "Sprogget" but may not be "Order00237"? I suspect that another DP type concern will be the extent to which the schema can be interpreted reliably at build time - when the design decisions are being made and agreed - as opposed to at run time, when the internal subset and parameter entities are instantiated... =[More Snips]= Francis. -- Francis Norton Old enough to remember free speech on the Internet? Catch http://www.oneworld.org/index_oc/issue298/frank.html while you still can. Or, indeed, if. 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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