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Subject: Proposed addition to 2.1 documented constraints - no schema location hints
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. 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. This isn't something we can say in the schemas, since a W3C Schema processor has these attributes built in. 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 -- Upcoming: hands-on code list, UBL, XSLT, XQuery and XSL-FO classes in Copenhagen Denmark and Washington DC USA, October/November 2009 Interested in other classes? http://www.CraneSoftwrights.com/o/i/ Crane Softwrights Ltd. http://www.CraneSoftwrights.com/o/ Training tools: Comprehensive interactive XSLT/XPath 1.0/2.0 video Video lesson: http://www.youtube.com/watch?v=PrNjJCh7Ppg&fmt=18 Video overview: http://www.youtube.com/watch?v=VTiodiij6gE&fmt=18 G. Ken Holman mailto:gkholman@CraneSoftwrights.com Male Cancer Awareness Nov'07 http://www.CraneSoftwrights.com/o/bc Legal business disclaimers: http://www.CraneSoftwrights.com/legal
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