- From: John Boyer <JBoyer@PureEdge.com>
- Date: Wed, 20 Mar 2002 10:35:20 -0800
- To: "merlin" <merlin@baltimore.ie>, <reagle@w3.org>
- Cc: "Christian Geuer-Pollmann" <geuer-pollmann@nue.et-inf.uni-siegen.de>, "TAMURA Kent" <kent@trl.ibm.co.jp>, <w3c-ietf-xmldsig@w3.org>
Hi Joseph and Merlin, <joseph> ... though there is still some confusion: Christian asking about what exactly Merlin is proposing [1], and my confusion about multiple transforms operating on the *original* document, not their preceding transforms output [2]. So before we have a call or resort to a poll I'd recommend we gather our thoughts and first reflect these changed in the document. Then we can further discuss as needed. </joseph> <merlin> To answer 2, in case it's not clear from my last message (which hopefully addresses 1), the XPath expression is evaluated in the context of the input document and then the result is applied to the input node set. </merlin> <jb> Yes, and I would further assert that the set operation transforms *are* operating over the output result of the preceding transform in a natural way, esp. given that we want to avoid running lots of XPath expressions. An Xpath evaluation context takes one node. If we want to run the Xpath over each node of the input, then use Xpath filter 1.0. Otherwise, we run one Xpath over the document from which the input node-set is drawn, then we perform a set operation between the Xpath result and the input node-set. Also, I think the fact that Xpath has a union operator has tricked us into believing that we don't need union as a third set operation. I think it's easy to implement and useful, e.g. Christian's examples can be solved if we add union as a third operation. I also think we should do it for the sake of completeness. </jb> <merlin> I think, as an aside, that a sequence of XPath, XPath filter and Enveloped signature transforms can thus be reordered without altering the resulting node set. </merlin> <jb> This is a neat property, but I don't think it a necessity, esp. not compared to having a union operation, which would eliminate the property. Thanks, John Boyer </jb>
Received on Wednesday, 20 March 2002 13:35:53 UTC