Re: [ubl] Proposed addition to 2.1 documented constraints - no schema location hints

["Roberto Cisternino" <roberto@javest.com>]

Hello Ken,

I have some comments,

> Hi folks,
>
> I'm preparing my training material for next week and something came
> to mind that I would like to consider for inclusion in UBL 2.1 along
> the lines of the additional document constraints.
>
> For example, we have in the additional document constraints section
> 6.3 that no UBL element can be empty.  There are two others.

It's good but not a good reason to block a B2B transaction.  Instead it is
more important to validate the existance of a mandatory information.

>
> I would like to add a new document constraint that schema location
> hints not be included in UBL documents, thus deprecating
> xsi:schemaLocation along the lines of:
>
>   <Invoice
>    xmlns:cbc="urn:oasis:names:...:CommonBasicComponents-2"
>    xmlns:cac="urn:oasis:names:...:CommonAggregateComponents-2"
>    xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"
>    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
>    xsi:schemaLocation="
>       urn:oasis:names:specification:ubl:schema:xsd:Invoice-2
>       u:/cd/artefacts/os-UBL-2.0/xsd/maindoc/UBL-Invoice-2.0.xsd
>    ">
>    .....
>
> Schema location hints are very platform and user specific.  Including
> such in an instance to a trading partner isn't invalid but could mess
> up that trading partner's processes that take advantage of such hints
> when available.  If their platform obliges them to edit out the
> attribute, then they are not dealing with untouched input instances.

>
> Per W3C Schema 2.6 all schema processors have this declaration
> built-in and thus the current UBL document constraint 6.1 is not
> violated when this attribute is present.
>
> But this introduces a new category of "additional document
> constraints" called something like "recommended additional document
> constraints" or "interoperability document constraints" because it
> cannot be mandated since it was not a rule for UBL 2.0.  Thus UBL 2.0
> instances may have it and we can't say in UBL 2.1 that a UBL 2.0
> instance is invalid.

I think it is up to XML engines to take advantage or not of XSI.
I think it is not useful to ask a software to test the existance or
non-existance of XSI as it is just a hint.

XSI should not confuse anyone when present.

Anyway I agree that today XSI is not so useful as we are required to use
XML Catalogs very often to resolve namespace URIs, and resolvers are a
stable concept into all XML Engines.

In fact when XML Instances are moved from one system to another we need to
resolve their namespaces in order to start a validation.

I think any actual xml engine should be able to validate the UBL structures.
So, in case we constraint the use of XSI, we should move this validation
into the 2nd phase.

>
> This isn't something we can say in the schemas, since a W3C Schema
> processor has these attributes built in.

right

>
> Having chosen the W3C Schema syntax to express the semantics of the
> document constraints has brought this in along as baggage ... if one
> were to create, say, a RELAX-NG model of the UBL schemas, that model
> would necessarily need to include in it a declaration of an optional
> xsi:schemaLocation to accommodate that it is implicitly allowed by
> our choice of schema expression.
>
> Therefore, I think we need a new section in the UBL documentation
> titled along the lines of "Interoperability Document Constraints"
> that documents recommended rules such as this that cannot be mandated
> (due to backward compatibility) but will improve interoperability
> between trading partners from UBL 2.1 and on.
>
> I'm curious to hear your thoughts on this.
>
> . . . . . . . . . . Ken

I agree to keep things in the right place and simple, however I am sure
that too many constraints will make people nervous.


>
> --
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-- 
* JAVEST by Roberto Cisternino
*
* Document Engineering Services Ltd. - Alliance Member
* UBL Italian Localization SubCommittee (ITLSC), co-Chair
* UBL Online Community editorial board member (ubl.xml.org)
* Italian UBL Advisor

  Roberto Cisternino

  mobile: +39 328 2148123
  skype:  roberto.cisternino.ubl-itlsc

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