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Re: with-option and other XPath Expressions - Prevent streaming from being possible (??)

From: David A. Lee <dlee@calldei.com>
Date: Fri, 5 Dec 2008 10:08:55 -0500
Message-ID: <89D54B62AC464F8394458D2F19CB5BED@calldei.com>
To: "Norman Walsh" <ndw@nwalsh.com>, "XProc Dev" <xproc-dev@w3.org>

Re:

>> DAL
> And this one sticky point could be what makes it impossible (or so
> extremely difficult that it wont ever be done) to have xproc ever work
> in a streaming mode in the majority of cases.
>> JW
I don't follow. How does splitting an input break streaming? The
splitter can stream, the downstream processes can stream, it's all
good. Just start a thread for each component and off you go...
-------

Splitting doesnt break streaming.  If the next stage in the streams dont 
depend on each other.

But evaluating an xpath in with-option does break streaming (to my mind).
This is because the options must be collected before the step can be 
executed.
Hence the stream needs to be split then the xpath expression evaluated 
(consuming its leg of the stream)
and the results of that evaulation fed into the step BEFORE the step can 
start.
Thats what breaks streaming.

Its possible I'm misunderanding this ... but if so could you explain how any 
parser could
execute a step in parallel before gathering and evaulating the option values 
(hence having to
read the entirety of the input).


As for objecting earlier ... If I'd started earlier I would have :)
But alas I'm late to the game.  Hoping not TOO late ...

-David Lee
Received on Friday, 5 December 2008 15:09:42 GMT

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