Re: A simple test of XPath filter performance

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
xpath-filter-subtract("/XFDL/page[@sid='PAGE1']/*[@sid='CHECK16'
or @sid='CHECK17' or @sid='FIELD47' or @sid='BUTTON2' or
@sid='FIELD48'] | /XFDL/page/triggeritem[not(@sid)]").

Merlin

r/JBoyer@pureedge.com/2002.05.08/11:59:26
>
>
>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"
>Filter="subtract">
>        /XFDL/page[@sid="PAGE1"]/*[@sid="CHECK16" or @sid="CHECK17" or
>@sid="FIELD47" or @sid="BUTTON2" or @sid="FIELD48"] |
>        /XFDL/page/triggeritem[not(attribute::sid)]
></XPath>
>
>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"
>Filter="subtract">
>        /XFDL/page[@sid="PAGE1"]/*[@sid="CHECK16" or @sid="CHECK17" or
>@sid="FIELD47" or @sid="BUTTON2" or @sid="FIELD48"] |
>        /XFDL/page/triggeritem[not(attribute::sid) |
>/XFDL/page/*/triggeritem]
></XPath>
>
>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.
>
>Thanks,
>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"] |
>/XFDL/page/*/triggeritem
>
>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]
>
>Merlin


-----------------------------------------------------------------------------
The information contained in this message is confidential and is intended
for the addressee(s) only.  If you have received this message in error or
there are any problems please notify the originator immediately.  The 
unauthorised use, disclosure, copying or alteration of this message is 
strictly forbidden. Baltimore Technologies plc will not be liable for
direct, special, indirect or consequential damages arising from alteration
of the contents of this message by a third party or as a result of any 
virus being passed on.

This footnote confirms that this email message has been swept for Content
Security threats, including computer viruses.
http://www.baltimore.com

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