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I don't have strong opinions on the value of doing this, but the case I noted earlier of a backchannel emerged at least in part when the developers celebrated their freedom from DTDs. That freedom came for other reasons - complex document structures and customer expectations of XML Schema - but somebody noticed the other possibilities. Using DTDs to put this genie back in the bottle may create other problems. And alas, I don't remember who told me this story, but I'm pretty sure it was after a New York XML Special Interest Group meeting. Thanks, Simon On 9/22/10 10:21 AM, Costello, Roger L. wrote: > David Carlisle suggested validating an XML document against a DTD as a mechanism for detecting unused namespaces. I tried it. It works well. > > I created this DTD: > > <!ELEMENT Root (child)> > <!ATTLIST Root > xmlns CDATA #FIXED 'http://www.used.org'> > > <!ELEMENT child (#PCDATA)> > <!ATTLIST child > xmlns CDATA #FIXED 'http://www.used.org'> > > > This XML document contains no unused namespaces: > > ----------------------------------- > <Root xmlns="http://www.used.org"> > > <child>true</child> > > </Root> > ----------------------------------- > > It validates fine. > > > Then I added an unused namespace: > > ----------------------------------- > <Root xmlns="http://www.used.org" > xmlns:foo="blah"> > > <child>true</child> > > </Root> > ----------------------------------- > > Validation fails. Good! Validation detected the unused namespace. > > > Conversely, this XML Schema does not detect the unused namespace: > > <schema xmlns="http://www.w3.org/2001/XMLSchema" > targetNamespace="http://www.used.org" > elementFormDefault="qualified"> > > <element name="Root"> > <complexType> > <sequence> > <element name="child" type="boolean" /> > </sequence> > </complexType> > </element> > > </schema> > > Validation succeeds with or without the unused namespace. > > > Conclusion: it appears that one mechanism for detecting unused namespaces in an XML document is to validate it against a DTD. Can anyone think of a case where a DTD would not detect an unused namespace? -- Simon St.Laurent http://simonstl.com/
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