Re: ietf-xml-use Non-sub: Re

[noah_mendelsohn@xxxxxxxxxx]

OK, let's try this again...

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Noah Mendelsohn                              Voice: 1-617-693-4036
IBM Corporation                                Fax: 1-617-693-8676
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----- Forwarded by Noah Mendelsohn/Cambridge/IBM on 12/12/2002 07:33 PM 
-----


Paul Hoffman / IMC <phoffman@xxxxxxx>
12/11/2002 06:02 PM

 
        To:     noah_mendelsohn@xxxxxxxxxx
        cc: 
        Subject:        Re: ietf-xml-use Non-sub: Re


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>  >From owner-ietf-xml-use Wed Dec 11 11:20:47 2002
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>To: Scott Lawrence <lawrence@xxxxxxxxxxxxx>
>Cc: ietf-xml-use@xxxxxxx, "Larry Masinter" <LMM@xxxxxxx>, www-tag@xxxxxx
>Subject: Re: XMLP WG Response on "SOAP and the Internal Subset"
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>Scott Lawrence writes:
>
>>>  Supporting entity substitutions other than the required minimum would
>>>  have had a fairly large effect on code size and complexity.  The
>>>  largest and most troublsome effect was on the buffer management - the
>>>  minimum required entities are all larger than the text that they turn
>>>  into internally, so they just collapse the data within the existing
>>>  buffer(s), but that's not true in the general case.
>
>Thanks Scott.  Turns out, this was among the optimizations we at IBM had
>noticed, and was among the ones I had in mind when preparing input to the
>XMLP workgroup response.  So, that's at least two independent
>organizations doing implementations with similar insights and intuitions
>regarding the tradeoffs involved in supporting entities.
>
>BTW:  several have asked whether there would have been a cost to allowing
>entities in the case where the instance did not in fact use entities.
>Well, as you say, there's often a cost in code footprint, unless you have
>a way of acquiring the code dynamically.  Unless you're very careful,
>there's also potentially a cost in terms of levels of indirection to the
>various potentially discontinguous buffers, unless you're willing to 
build
>two versions of your code and switch to the "no buffer management" 
version
>when you discover that there are indeed no entity definitions.  That also
>involves more testing cost for the alternate paths, etc.  Regarding those
>who have asked for specific performance numbers, I can't say that we in
>IBM have built controlled implementations, one with and one without just
>the internal subset optimizations.    As I said in my earlier note, one
>tends to make combinations of optimizations together.  Our experience is
>that in combination it is possible to use such techniques to get very
>significant improvements over what would be typical of full function
>parsers.
>
>------------------------------------------------------------------
>Noah Mendelsohn                              Voice: 1-617-693-4036
>IBM Corporation                                Fax: 1-617-693-8676
>One Rogers Street
>Cambridge, MA 02142
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