[Haskell-cafe] Re: HXT Namespaces and XPath
mads_lindstroem at yahoo.dk
Wed Apr 7 06:27:42 EDT 2010
> Hi Mads,
> > Replying to myself:
> > > I think another example will clarify my point. The code:
> > >
> > > simpleXmlOne, simpleXmlTwo :: String
> > > simpleXmlOne = "<a:Foo xmlns:a=\"http://foo.org\"/>"
> > > simpleXmlTwo = "<b:Foo xmlns:b=\"http://foo.org\"/>"
> > >
> > > nsEnv :: [(String, String)]
> > > nsEnv = [ ("notFoo" , "http://notfoo.org") ]
> > >
> > > evalXPath :: String -> [XmlTree]
> > > evalXPath xml =
> > > runLA ( xread
> > > >>> propagateNamespaces
> > > >>> getXPathTreesWithNsEnv nsEnv "//a:Foo"
> this line contains the problem:
> getXPathTreesWithNsEnv assumes, that for all prefixes used in the XPath expr,
> the nsEnv contains an entry. Furthermore the default namespace
> can be given by an entry for the empty prefix "".
> So you'll only get reasonable results, when nsEnv contains at least an entry for "a", e.g.
> nsEnv = [ ("a", "http://x.y"), ... ]
> when you use the XPath expr "//a:Foo".
> You may argue, that in your example, an error should be raised by the XPath parser, instead
> of accepting "//a:Foo". But currently it's assumed, that getXPathTreesWithNsEnv is used
> only in an innocent way.
Yes, that was what I would have expected.
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