Re: Help - any/anyAttribute - notNamespace, notQName
Other than the points I shared below, I think using assertions to meet the validation objectives that can be accomplished by notNamespace and/or notQName for example, is not good in a sense that assertion evaluations require an XDM tree in memory (building this tree is an overhead for the XML schema validator -- both processing and memory footprint). Therefore my recommendation is not to use XML schema assertions, if the XML instance objectives can be achieved by notNamespace and/or notQName. On Fri, Dec 17, 2010 at 1:37 PM, Mukul Gandhi <email@example.com> wrote: > Hi Ram, > Â Â It seems you're referring to XML Schema 1.1 assertions. The > definitions cited in your examples are *not* syntactically correct > (xs:assert could not be a child of xs:any). > > XML Schema assertions are defined at a level of complexTypes (and also > as facets on simpleType's). For e.g something like: > > <xs:complexType name="MYTYPE"> > Â Â <xs:sequence> > Â Â Â Â <xs:any /> > Â Â </xs:sequence> > Â Â <xs:assert test="not(namespace-uri() = 'http://www.example.org')" /> > </xs:complexType> > > But here are the issues I see with using assertions on xs:any wild-card: > 1. For xs:any (i.e with the wild-card "strict" mode) the element > instance will be validated by the element particle in scope of the > validation episode. Therefore any constraint on the wild-card via > assertions (for e.g a namespace constraint that you've specified) may > conflict with the targetNamespace of the element particle. Since > affect of assertions is a boolean and to the element particle > constraint in this case, I think using assertions for wild-card strict > mode is a poor XML schema design. > 2. For xs:any with "lax" mode, I see assertions to have few valid uses > but only if there is no element particle available to validate the > corresponding element instance. Again if an element particle is > available in scope to validate the XML information item, then effect > of assertions is a boolean and to the element particle constraint, > which to my opinion is not a good design. > 3. For xs:any with "skip" mode, I do not see any good uses of XML > schema assertions. In case of Xerces for xs:any wild-card "skip" mode, > the corresponding element information items are not available in the > XDM tree on which assertions operate, therefore assertions are not > much useful for wild-card "skip" mode. > > To my opinion, using the XML schema component attribute instructions > notNamespace and notQName is a better idea to have constraints on > namespace and Qname's of information items (the elements and > attributes) instead of using schema assertions. > > I think assertions would be more useful when bound to wild-card > instructions, for e.g to place constraints on aspects of child tree > (like how many children, white space constraints etc) of the root > element information item. -- Regards, Mukul Gandhi
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