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Subject: RE: [ubl-ndrsc] ur-schema necessitates xsi:type everywhere in instance
This isn't my understanding, or at least it is only one possible interpretation. I would take it as a given that it is unacceptable to require xsi:type on every element. This is hardly likely to encourage adoption of UBL. Hence, UBL document types should reference UBL types/element in their content models. If you want to use the ur-type of a type, you need to use the ur-type of the document type as well. In this way you put the onus on the ur-type users, which seems appropriate since they are likely to be the minority. Matt -----Original Message----- From: Burcham, Bill [mailto:Bill_Burcham@stercomm.com] Sent: Wednesday, February 05, 2003 3:40 PM To: 'Lisa-Aeon'; UBL-NDR Subject: [ubl-ndrsc] ur-schema necessitates xsi:type everywhere in instance One issue with ur-proposal that was not discussed was this issue (from a private message I produced on Monday -- also, see the attachment): ... I worked out a little example of the ur-type proposal a while back. I think I've forwarded it before, but to save you groveling about the list I've attached it again. I've made a namespace for ur-types and a dervied one for "UBL types". Then I made a third for a "third-party-restriction". A key issue we identified with Paella is as far as I can tell, still an issue with the latest ur-type proposal. If you look at a "vanilla" UBL instance document (ubl-doc.xml) you see it has to use xsi:type on every element. The same holds for a "customized" UBL instance document (third-party-restriction-doc.xml). The reason this happens is that every element declaration must be of an ur-type -- never a (derived) UBL type, or a (derived) customized type. It must be so since this is the means by which we are able, after the fact, to derive from the ur-type without the horrendous "cascade" back through all the referenceing content models (and the ones that reference those, and so on -- remember Barcelona). The fact that the instance documents must carry xsi:type everywhere means that schema validation is _not_ (on its own) enforcing a particular vocabulary -- I can really use an ur-type wherever I want to and the schema validator isn't going to squawk. If that's the case, then what, exactly is the value of the UBL namespace (i.e. the non-ur-types)? I mean, should we just ship the "everything is optional" ur-types and be done? Maybe I misunderstand the proposal. If so, could someone please correct my simple example and show me some new instance documents that don't require xsi:type everywhere? Barring that we should probably revisit our discussion from last March and decide whether that's ok, or whether we need to fix it somehow (and no, I don't have any ideas just now :-) One thing I have tried is to get the xsi:type attributes on the elements in ubl.xsd to _default_ to the UBL types somehow... But I fear I am not nearly the XSD wizard for that task -- heck I can hardly even describe it.
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