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Re: A simple test of XPath filter performance

From: merlin <merlin@baltimore.ie>
Date: Mon, 13 May 2002 20:21:05 +0100
To: "John Boyer" <JBoyer@pureedge.com>
Cc: w3c-ietf-xmldsig@w3.org
Message-Id: <20020513192105.33F0F4431D@yog-sothoth.ie.baltimore.com>

Hi John,

I hesitate to give actual performance figures because the
only machine I have for testing is a live server that
has just 256M of memory and is running .5G into swap,
so may be unrepresentative; however, a 'warm' signing
application (java, linux, 500MHz athlon) performs a
full 1024-bit DSA XML signature generation over your
XFDL example in 160ms (enveloped signature followed by
or @sid='CHECK17' or @sid='FIELD47' or @sid='BUTTON2' or
@sid='FIELD48'] | /XFDL/page/triggeritem[not(@sid)]").


>Hi Merlin,
>Yes it should be an enveloped signature.  
>Our software automatically adds an XFDL type signature element and
>populates with all of the information you see in the signed leave
>request form.  It also automatically omits the 'mimedata' element that
>contains the results of the signature.  So, there will be some
>differences, but it does look like your output  has no meaningful
>differences.  The main question is how long it took for the signature to
>be created.  My hope is that it was very fast; the ideal would be to
>match or beat the performance of the current PureEdge software, which
>means less than half a second on a 500MHz intel machine for filtering,
>c14n, hashing/cryptography, and signature element completion.
>As for the triggeritem, it does not appear in the sample because we are
>simulating a piece of future work that must be done to the form.  So,
>you should be able to change "<page sid="PAGE1">" to "<page
>sid="PAGE1"><triggeritem>SubmitButton</triggeritem>" without breaking
>the signature.
>However, note that I did make an error in the suggested filter
>expression.  Internally, our document tree representation has the
>triggeritem as a grandchild of the page (because it puts all page global
>options into an implicit page global item).  In the actual markup,
>though, the triggeritem is a child of the page, distinguishable from
>regular items like 'button' and 'field' by the fact that triggeritem has
>no scope identifier attribute (i.e. it has no 'sid').  The correct XPath
>Filter 2.0 transform should be:
><XPath xmlns="http://www.w3.org/2002/04/xmldsig-filter2"
>        /XFDL/page[@sid="PAGE1"]/*[@sid="CHECK16" or @sid="CHECK17" or
>@sid="FIELD47" or @sid="BUTTON2" or @sid="FIELD48"] |
>        /XFDL/page/triggeritem[not(attribute::sid)]
>Note, however, that this change of filter should make this example
>*faster* than what can be achieved with the current PureEdge software,
>which treats the triggeritem filter as mostly a grandchild test (i.e. it
>eliminates triggeritem elements with no sid from the page child level
>*and* it eliminates triggeritem grandchildren of the page element).  To
>truly simulate what the PureEdge software does, the following transform
>would be required:
><XPath xmlns="http://www.w3.org/2002/04/xmldsig-filter2"
>        /XFDL/page[@sid="PAGE1"]/*[@sid="CHECK16" or @sid="CHECK17" or
>@sid="FIELD47" or @sid="BUTTON2" or @sid="FIELD48"] |
>        /XFDL/page/triggeritem[not(attribute::sid) |
>I mention this only to illustrate that there is no magical,
>hyper-optimized code behind the PureEdge software's processing of the
>'signoptions' filter. It is essentially a subtree subtract filter that
>visits a lot of nodes.
>John Boyer
>-----Original Message-----
>From: merlin [mailto:merlin@baltimore.ie]
>Sent: Wednesday, May 08, 2002 10:36 AM
>To: John Boyer
>Cc: w3c-ietf-xmldsig@w3.org
>Subject: Re: A simple test of XPath filter performance 
>Hi John,
>I attach a tgz file with signatures that covers the spec
>examples and your XFDL document. The XFDL signature is
>just stuck in the middle and has:
>  URI=""
>    enveloped-signature
>    subtract /XFDL/page[@sid="PAGE1"]/*[@sid="CHECK16" or @sid="CHECK17"
>or @sid="FIELD47" or @sid="BUTTON2" or @sid="FIELD48"] |
>Is this the manner of signature desired? Is the triggeritem
>a child of page/*? Should it be an enveloped signature or
>subtract /XFDL/page/dsig:Signature?
>[Christian: your examples work fine for me]

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Received on Monday, 13 May 2002 15:21:08 UTC

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