RE: [xacml] Namespaces and xpaths

["Daniel Engovatov" <dengovatov@bea.com>]

It seems that our XPath binding is underspecified - we need to define
the in scope namespaces resolution (things that XQuery does in its
prologue) and define the content node (".")
Minimal list that we need to define is in appendix D of the XPath 2.0
document: http://www.w3.org/TR/xpath20/#id-impl-defined-items, Section
F.1 and F.2 in XDM document:
http://www.w3.org/TR/xpath-datamodel/#implementation-defined and
Appendix F in F&O spec: http://www.w3.org/TR/xquery-operators/#impl-def

That is a fairly long list that may require its own mini-spec.   I have
filed a work item on this, so I guess I would own the list.

Daniel;


-----Original Message-----
From: Erik Rissanen [mailto:mirty@sics.se] 
Sent: Thursday, March 29, 2007 5:31 AM
To: xacml@lists.oasis-open.org
Subject: [xacml] Namespaces and xpaths

All,

I have a question about namespaces and xpath expressions. There are a
few standard xpath functions in XACML 2.0 in section A.3.15. These
functions take strings as parameters, where the strings are to be
interpreted as xpath expressions.

How is resolving of namespace prefixes in these strings/expressions
done? The specification doesn't say anything about this. (Or I didn't
find it.)

Is the xpath function going to trace back its input to the xml document
from where the string came from? This doesn't seem possible in general.
Or does it find the <Apply> element from where the invocation came, and
use only those declarations? But this is confusing since the string may
originate from somewhere else.

Maybe we need an xpath expression data type to embed the namespace
associations with the expression? I think such a type would be valuable
also if users create new xpath related functions.

If we define such a data type, we could also define a cast from a
string, in which case no namespaces will be defined.

Similarly, there is no text about namespace resolving in the text about
<AttributeSelector>, but here it seems obvious that the xpath matching
must use the namespaces in effect at the <AttributeSelector> element.
But maybe some text would be good anyway?

Regards,
Erik


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