XML Processing Model WG

Meeting 20, 11 May 2006


See also: IRC log


Murray, Norm, Henry, Alessandro, Richard, Rui, Alex
Andrew, Michael, Paul


Accept this agenda?

-> http://www.w3.org/XML/XProc/2006/05/11-agenda.html


Accept minutes from the previous teleconference?

-> http://www.w3.org/XML/XProc/2006/05/04-minutes.html


Next meeting: 18 May 2006

Already regrets from: Andrew, Michael, Henry


Please register: http://www.w3.org/2002/09/wbs/38398/XProcFTF2/

Local arrangements: http://www.w3.org/XML/XProc/2006/08/02-04-f2f.html

Norm hopes we can nail down the transport next week.

Review of open action items

  1. A-19-01: Alex to send mail describing his ideas about variables.
    • Continued
  2. A-19-02: Norm to create an issue about the variable/parameter/input/output binding framework.
    • Completed
  3. A-18-01: Alex to create an issue about the possibility of functional components
    • Completed
  4. A-17-02: Murray to provide local arrangements info for August
    • Completed
  5. A-13-01: MSM to draft a complete table; ETA: 15 June 2006
    • Continued.

Issue 3089: What version/subset of XPath is used in conditionals?

-> http://www.w3.org/Bugs/Public/show_bug.cgi?id=3089

MoZ: are you trying to dial in and not getting through the bridge?

Norm: Three possibilities, 1) use someone else's streaming subset, 2) invent our own, 3) use full XPath and leave it as a QoI issue

Alex: Although I use a streaming subset, I think that's an optimization. I think we shouldn't have a subset.

Norm: I can find off-the-shelf full XPath 1.0 implementations, so I think that answer makes it easiest to get started
... Is there anyone that thinks we need to define a subset?

Henry: I'm uncomfortable, but I'm willing to leave it for CR.

Norm: That works for me.

Richard: Do we have a good idea of what circumstances these XPaths are used in

Norm: Off the top of my head, we've got: conditionals, peepholing

Richard: Also the "replacement" component
... It's possible that that's a component by itself.

Norm: so those wouldn't have to be the same.

Richard: I think I'm happy for it to be full XPath 1.0 and I can detect some streamable queries.

Proposal: We will use XPath 1.0 in our language

Alessandro: I think it will be interesting to have XPath 1.0 vs XPath 2.0 question

Alessandro: At least in the environment I am working in, off-the-shelf 2.0 implementations are easy to come by.

Norm: Do you have a use case in mind for pipeline conditionals?

Alessandro: Not off the top of my head

Alex: We could declare what version of XPath the pipeline uses and implementations can reject pipelines they can't support.

Richard: Isn't it the case that if you have XPath 2.0, you have to worry about whether the data has schema type and so on.
... I know that there are XSLT 2.0 implementations that don't support the schema stuff and can give different answers.
... If we introduce XPath 2.0 are we introducing new levels of conformance.

Norm: Yes, I think they would.
... This seems useful and interesting, but not necessary.

Norm observes, in response to Richard, that having XPath 2.0 would mean that the pipeline engine would have to be able to import schemas

Alessandro: In environments where 2.0 is available, requiring XPath 1.0 seems like a burden

Norm prefers a single choice for interoperability

Alex: By the time we become a recommendation, we have to have a cohesive store around XSLT 2.0, XPath 2.0, XQuery, etc.
... I don't think we can push that to V.next, we need to come out with a recommendation that works well with those technologies.

Norm: Wow. Ok.

Norm worries that dealing with those things in 1.0 makes our goal of finishing this year hopeless.

Alessandro: I agree that there's complexity, but I think we should try just a little bit harder to try to accommodate schemas and XPath 2.0
... It might be the case that we come to the conclusion that we can't do it in 1.0

Murray: I would tend to agree with Norm, let's do something we can accomplish in the timeframe we set out, even if it isn't' as grand and robust and wonderful as we might achieve in the fullness of time.
... We can move onto the next stage afterwards.

Norm: Can Alex/Alessandro make some proposals to see if you can convince us that using schemas, XPath 2.0, etc. is achievable in our timeframe?

Alessandro: yes

Alex: yes

Proposal: We will assume full XPath, not a streaming subset, in the language (unless and until we get pushback from implementors)


Issue 3198: Functional components?

-> http://www.w3.org/Bugs/Public/show_bug.cgi?id=3198

We've already made a decision about this, this issue is just for the future

Issue 3199: How do pipeline parameters, inputs, and outputs interact?

-> http://www.w3.org/Bugs/Public/show_bug.cgi?id=3199

We don't really have any clear ideas about exactly how these things fit together yet

Norm reviews Richard's ideas that started this

Richard: Fundamentally, it must be possible to get some output into a parameter.
... The simplest way to define a parameter is to give a literal value.
... The next way up would be to give an XPath and the output of some other component to apply it to. It would evaluate the expression and the result would be the value of the variable
... So the temporary file component could generate a document and the XPath expression could be "."
... This means that all these things are connected by plumbing.
... Other people have mentioned at various times mechanisms for having variables that are in scope, etc. But I think the simple method is a good starting point.

Norm: I had in mind setting variables in general being specified with XPaths (so that pipeline params could be composed from command line params (for example) and others.
... I was thinking of evaluating them all with an empty document node as the context.
... Extending that to allow them to specify an input document makes sense.
... Is that sufficient?

Henry: It ought to be possible in a pipeline definition to say that the value of some step parameter is referred to at the pipeline level

Scribe isn't sure that he recorded Henry correctly

Norm: Parameters could have two attributes: value and select for literal values and XPath expressions

Some discussion about how these things get connected together syntactically.

Richard: I think the 90% case is that variables are constants. It's reasonable for it to be slightly complicated.

<scribe> ACTION: Norm to write up his thoughts on parameters and inputs [recorded in http://www.w3.org/2006/05/11-xproc-minutes.html#action02]

Alex: This is related to the variables action that I have

Richard: It would be nice if this mechanism was extensible to being able to having different variables in scope in different parts of the pipeline.
... But it's not immediately clear to me how it is. But maybe it is.

Any other business?



Summary of Action Items

[NEW] ACTION: Norm to write up his thoughts on parameters and inputs [recorded in http://www.w3.org/2006/05/11-xproc-minutes.html#action02]
[End of minutes]

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$Date: 2006/05/25 16:28:16 $