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Subject: RE: [xacml] xpath-expression datatype


On Fri, 27 Aug 2004, Anne Anderson wrote:

> existing functions.  Yet I think "string to be interpreted as an
> XPath expression" does not give implementers or policy writers
> sufficient type checking capability.  I can also see extension
> functions defined that would use an "xpath-expression" datatype,
> and those would not necessarily be for hierarchical resources.
>
> I suggest we extend the definition of the existing XPath-based
> functions in A.3.14 to accept EITHER "...#string" OR
> "...:xpath-expression", and indicate that "...#string" is
> deprecated.  And then leave the definition of the
> "...:xpath-expression" datatype in the core specification.  This
> does not break backwards compatibility.

That will break the type system.

> Another option would be to re-define the XPath-based functions in
> A.3.14 with new identifiers: urn:oasis:names:gc:xacml:2.0:...,
> and then change the definitions to use "...:xpath-expression".
> Then 2.0 implementations that are backwards compatible can
> continue to support the 1.0 versions, but the 2.0 versions can be
> strongly typed.

That would be the better way.

Still, there seems to be a desire to "build" these expressions on the fly.
So, you in order to use the string functions to make them, you would need
a type coercive function that takes a string type to an xpath expression
type. It's not a do nothing function either.  (This function would have
the added benefit of throwing an Indeterminate if what you built on the
fly was an invalid xpath expression).

Cheers,
-Polar

> Anne
> --
> Anne H. Anderson             Email: Anne.Anderson@Sun.COM
> Sun Microsystems Laboratories
> 1 Network Drive,UBUR02-311     Tel: 781/442-0928
> Burlington, MA 01803-0902 USA  Fax: 781/442-1692
>
>
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