xpath filter

[Martin Bjorklund <mbj@tail-f.com>]

Hi,

I know that this has been up on the list before, but I never saw any
replies.  The question is how to handle namespaces with the xpath
capability.  Consider the example in 8.9.5.1:

         <filter type="xpath"> <!-- get the user named fred -->
           top/users/user[name="fred"]
         </filter>

If the box supports multiple namespaces, which namespace does top
belong to?  You could argue that this is a filter, so it should return
results from all namespaces which match the filter.  But what if you
want to explicitly match a certain namespace?

The XPath specification says that an xpath expression is evaluated
with respect to a context
(http://www.w3.org/TR/xpath#section-Introduction).  A context
contains, amongst other things, the set of namespace declarations in
scope for the expression (a mapping from prefixes to namespace URIs).

As one example, XSLT defines the context in
http://www.w3.org/TR/xslt#section-Expressions.  It defines the
namespace declarations as:
  
  the set of namespace declarations are those in scope on the element
  which has the attribute in which the expression occurs; this
  includes the implicit declaration of the prefix xml required by the
  the XML Namespaces Recommendation [XML Names]; the default namespace
  (as declared by xmlns) is not part of this set


I suggest that NETCONF uses a similar definition, so that one can
write a filter such as:

  <filter type="xpath" xmlns:d="http://www.example.com/Datamodel";>
     d:top/d:users/d:user[name="fred"]
  </filter>

Also, I think that the XPath Core functions should be sufficient for
NETCONF compliance; this is also not defined in the current draft.


/martin

--
to unsubscribe send a message to netconf-request@ops.ietf.org with
the word 'unsubscribe' in a single line as the message text body.
archive: <http://ops.ietf.org/lists/netconf/>