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RE: Call for Review: XML-Signature XPath Filter 2.0

From: <DPawson@rnib.org.uk>
Date: Tue, 3 Sep 2002 10:10:10 +0100
Message-ID: <9B66BBD37D5DD411B8CE00508B69700F024A79FF@pborolocal.rnib.org.uk>
To: w3c-ac-members@w3.org
Cc: www-tag@w3.org

> Subject: Call for Review: XML-Signature XPath Filter 2.0 

From which:

<quote>
In the interest of simplifying the creation of efficient implementations,
the architecture of this transform is not based on evaluating an [XPath]
expression for every node of the XML parse tree (as defined by the [XPath]
data model). Instead, a sequence of XPath expressions are used to select the
roots of document subtrees - location sets, in the language of [XPointer] -
which are combined using set intersection, subtraction and union, and then
used to filter the input node-set. The principal differences from the XPath
transform are:

A sequence of XPath operations can be executed in a single transform,
allowing complex filters to be more-easily expressed and optimized. 
The XPath expressions are evaluated against the input document resulting in
a set of nodes, instead of being used as a boolean test against each node of
the input node-set. 
To increase efficiency, the expansion of a given node to include all nodes
having the given node as an ancestor is now implicit so it can be performed
by faster means than the evaluation of an XPath expression for each document
node. 
The resulting node-sets can be combined using the three fundamental set
operations (intersection, subtraction, and union), and then applied as a
filter against the input node-set, allowing operations such as signing an
entire document except for a specified subset, to be expressed more clearly
and efficiently. 
</quote>

I thought one of the architectural principles was re-use.
With xpath 2.0, most of these differences appear to be resolved.
Why can't a little more coordination ensure that xpath can be used
for signatures?

Regards DaveP.

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Received on Tuesday, 3 September 2002 05:10:32 GMT

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