[ubl-ndrsc] ur-schema necessitates xsi:type everywhere in instance

Title: Message 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

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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 thin g 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.
Attachment: ur-example.zip Description: Binary data