Cart
|
[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Flexible Schemas (was RE: The task to be solved by RDDL)
 > > And I'm not talking about exotic, rare and proprietary schemas. To begin > > with, some examples are all XHTML documents that have modules in other > > namespaces, like RDDL and WAP 2.0. There are DTDs and schemas for those > > language, but RDDL is not fit to handle them. > > As I said in my previous message, I don't see this as a problem with RDDL. As I've said three of four times now, show me the algorithm that will find the URL of the RDDL document for this document : http://www.rddl.org/. This is a FONDAMENTAL problem with RDDL. > Instead I think it suggests that our approach to writing *schemas* isn't > flexible enough to deal with documents containing an arbitrary mix of > namespaces. I should state up front I don't have any answers here, > I'm just interested in a general discussion. > > The majority of schemas that I've seen assume a fixed set of > elements. These elements may come from zero, one or more namespaces. > The schema is "closed". They're designed to validate a particular > class of documents. > > Some schemas are "open", i.e. they allow "unknown" elements to be > used in the document, and these usually in fairly fixed places (cf: XSD > ANY, XHTML DTD Modularization). However these schemas still seem > to be designed to validate _documents_. They validate the document, > and ignore sections of it, or as with modularization defer to other > schema/dtd modules. > > Yet the scenario you're discussing is one which seems like it could > become increasingly common: we have a mixed namespace document > for which there is no schema. You're asking, how can I validate > these documents? Is there a heuristic for combining together several > schemas to achieve this goal? In fact there are schemas for RDDL and WAP 2.0, DTD are provided for both examples. Nothing prevents a schema from manipulating names from different namespaces. However, the scenario I'm discussing is a scenario where the document has not a single namespace, breaking the false but too often believed assumption that a namespace name is equivalent to a DOCTYPE specification. Regarding "open" schema, that is to say schema that are meant to be extended or inherited, there is indeed a problem. I think namespaces are part of the solution, but are in no way THE solution. > To do this you need to define schemas not only to be open, but also > to be easily fragmented so that portions of it can be applied. I can > imagine doing this with a schematron schema (only apply certain rules/patterns), > but not with a DTD. I also assume there's a way to do this with RELAX NG > and XSD. You then need to apply these fragments to the document to > validate it. Yeah, I think that in opened schemas, partial validation of "patterns" are required, instead of global validation of whole documents. This can be done with the current schema languages, though, even DTDs. I tried to write down some thoughts about it there : http://nicolas.lehuen.com/Articles/Programming/Ideas/fog0000000033.html > > I don't see schemas being written with this use in mind, nor do I see > validators that allow this flexible application of schemas. > > I may be showing a lack of understanding here, I don't mind > looking a fool :) Does anyone else see this as an issue, or is it > not a problem? Am I misunderstanding something? > > RDDL only enters this picture as a way to associate a schema, or > fragment thereof with a Namespace URL. Doing something with those > fragments, assuming they're available is something for the validator. Schemas can be associated to namespace (one or many namespaces), but the contrary is, IMHO, a bad idea. I am sorry, but I don't see how to solve this problem without relying on the concept of document or element type. I'll try to expand on this in the article mentionned above. Regards, Nicolas > Cheers, > > L. > > -- > Leigh Dodds, Research Group, Ingenta | "Pluralitas non est ponenda > http://weblogs.userland.com/eclectic | sine necessitate" > http://www.xml.com/pub/xmldeviant | -- William of Ockham > > 
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! 
Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|
|||||||||
