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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: dynamically generated XML Schema?! Re: R: [xml-d
 Hi Michael > > That's actually four levels already: unicode encoding, XML well-formedness, > schema validity, and application validity. And yes, you often need multiple > levels. > The first 2 levels you mentioned are not configurable. I had lumped the first 3 stages you have mentioned into one. Schema validity is the right technical term to use, my humble apologies. > But that doesn't stop you wanting individual levels to be configurable. A > very simple example, when I validate new documents I want to check that the > date is today. That kind of thing is very easily achieved by a configurable > schema. With all due respect, this is a trivial example becaue the today context is implicit. However, I must add that the angle where your idea comes from is brilliant ! Honestly, I have not thought of this before, but isn't this not a complex solution to a simple problem ? If I have to do this validation at the schema level, I would have to factor Today either as a regular expression or into its facets, taking into consideration 8601 constrains and time zones. If this is done at the application validity (2nd stage) phase, it would probably only entail a simple comparison to a Today constant. I have not taken this path before to discuss in exact implementation details, so I may be wrong. The scenario is however vastly different if we are in a workflow app, external context aside, we cannot assume some state without first looking into the document right ? > Equally, the application-level validation is often done using XSLT > stylesheets, and people often transform stylesheets for the same reason: you > need things to be configurable at that level too. > Sure, my point is that the logical stuffs should be kept here and not moved into the Schema validity space through dynamic schemas. I suspect, even if XML Schema evolved to provide conditional validation in the distant future, we still cannot completely escape the application-level validation layer. The XML Schema must still be emphsized as a means to enforce an agreed vocabulary and not become dependent on application/system semantics. The trick is therefore to strike the correct balance by putting each validation requirement into the correct layer. best rgds, Kuan Hui 
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