XML Processing Model WG

6 Apr 2006


See also: IRC log


Alessandro, Andrew, Henry, Mohamed, Norm, Rui
Erik, Jeni, Michael, Richard, Paul


Accept this agenda?

-> http://www.w3.org/XML/XProc/2006/04/06-agenda.html


Accept minutes from the previous teleconference?

-> http://lists.w3.org/Archives/Public/public-xml-processing-model-wg/2006Mar/0069.html


Next meeting: 13 Apr telcon

Any regrets?

No regrets given

Publication status

Norm submitted the transition request and got approval.

Norm submitted the publication request dated 11 Apr 2006

-> http://www.w3.org/XML/XProc/docs/WD-xproc-requirements-20060411/

Face-to-face meeting: 2-4 August 2006, north of Toronto

Norm proposes: who can commit to attending?

Rui: unsure; Norm: yes; Alessandro: unsure (also for Erik); Henry: yes; Mohamed: unsure, but probably; Andrew: no; Paul: yes; Henry says Alex, Michael, Jeni say yes; Richard: unsure

Tally: 7=yes; 5=unsure; 1=no

Proposed: we will meet in Toronto on the dates specified.


Henry points out that formally we can't decide to do this, all we can do is ask the CG to allow us. No one seriously expects the CG to say anything but "yes"

<scribe> ACTION: Norm to get this into the CG calendar [recorded in http://www.w3.org/2006/04/06-xproc-minutes.html#action01]

Starting a working draft

The chair asks if we have a volunteer editor.

Norm volunteers.

Norm warns that editing, chairing, and taking minutes may prove too much for one person. He suggests that Henry, Michael, and perhaps others may get called upon to take minutes.

Norm wonders if rotating the minute taking is the right thing.

Richard's proposal

-> http://www.cogsci.ed.ac.uk/~richard/pipeline.html

Norm wonders if it makes sense to consider Jeni's proposal of passing URIs instead of documents around.

Henry doesn't think passing filenames (URIs) around is really going to work.

Henry: Jeni's story could be read either way (as passing filenames or using filenames)
... I'm still interested in thinking about this in terms of giving local names to things (inputs/outputs) and using those names to refer to them.

Norm: With respect to giving names to local things, did you mean inputs and outputs

Henry: Yes, but I also mean static resources/secondary inputs/whatever you want to call them.
... In the pure piped ontology which Richard offered at the f2f, there is a qualitative difference between an XSLT component that has one pipe coming in and one going out and a parameter which is the name of a static stylesheet and an XSLT component that has two pipes coming in and one going out.

Norm: My proposal, to unify these, is to allow a shortcut for a "read-from-URI" component that attaches to the stylesheet input pipe.
... Do you see any problem with that approach?

Henry: No, but I'm still swinging back and forth between thinking of the pipeline runtime as a resource manager and the pure dataflow model.

Norm: I tend to swing back and forth as well. I hope that we don't have to pick one.
... The resource manager view has the problem of dealing with a pipe that contains a sequence of otherwise anonymous docments.

Henry: Local names are just conveniences. They are single documents or doucment streams as appropriate.
... The only interesting case is when you use a non-local name.
... In MT pipe, the convention is if you use a #-ed name, it just plugs together. If however it's a primary input/output connection and you give it a non-#'d name, then you get the single document if it's one or the last document if it's a sequence.
... There's no clear answer to the question of what does the label mean if a sequence of documents is addresed by a lable in the resource-manager view.

Norm ponders the idea of a resource manager that handles a collection

Norm suggests the fragment question as a next reasonable point to discuss

Norm describes the situation as an interoperability issue (since some implementations might not even notice and others might fall over)

Henry: It's entirely reasonable for some implementations to fall over if you pass anything other than real XML "Document"s .

Norm expresses a view that either the pipeline author has to fix it, or the pipeline engine has to fix it.

Norm: I suggest for V1 that we say it's the pipeline author's problem

Henry: works for me

Norm wonders if the rest of the group agrees

Rui: I believe that just documents is good enough for me.

No one objects.

Proposal: only XML 1.x documents (proper Documents in the XML sense) pass between components; if you need to pass something else in your pipeline, the pipeline author has to wrap and unwrap as necessary.


<scribe> ACTION: Norm to begin summarizing the points of consensus [recorded in http://www.w3.org/2006/04/06-xproc-minutes.html#action02]

Conditionals and sub-pipelines

Norm: Richard proposed a single standard conditional that takes a document and an XPath, is that enough?

Norm wonders if the WG thinks that's all we need

Henry: If you need something really complicated, you can write an arbitrarily complicated computation that produces a document.
... And then switch on that conditional.

Proposal: The pipeline conditional component is XPath expression over document. If you need more, build a document and use that?


What about XPath 1 vs. XPath 2?

Murray: We could put the statement in terms of the available processor.

Norm suggests that won't work

Henry: Several possibilities:
... 1. Use a convention for naming XPath expressions that are the values of attributes; xpath=, xpath1=, or xpath2=
... A question we have to address is, are we going to subset XPath in order to guarantee that it isn't hard to do this.
... I think we should subset.

Henry proposes that the XPath expressions that you can use in conditionals to being ones that are streamable

<MoZ> ht, what about attribute minxpathversion="1.0" to parse

Henry: bearing in mind again that if you need the full power of XPath, then you can use an XSLT processor to build a document ove rwhich a streaming test will succeed.

Alessandro: We can say that the expression is going to be XPath 1 or 2 and the engine can analyze the expression and stream if it wants to. Otherwise, it can just run a full XPath engine

Norm asks if Alessandro is opposed to the subset

Alessandro: Yes

Henry: The problem I have is that it puts a huge burden on the implementor for functionality that we've already determined most users won't ever use

Norm: My concern is inventing the subset. Do you think the XML Schema schema subset is appropriate.

Henry: Not quite.
... The thing that's missing is [@foo]

Norm: So the tradeoff is inventing a subset or using an off the shelf processor. Or is the problem really the analysis for streaming?

Henry: The analysis is hard. Can we float a trial balloon and examine the possibility of using that in V1?
... Two issues for V.next are, should we accept any XPath or should we require people to detect a certain class as streamable

Norm: Why detect? Non streaming will always work.

Henry: One of the crucial things about a viewport is that the XPath expression be streamable because that's how you deal with documents that are too large to read into memory.
... Conditionals are not the only place where XPath expressions are going to turn up.
... It seems plausible to try to tell a consistent story.

Norm: I agree, I don't want XPaths on different components to have a different flavor.

Henry: Maybe the regex for detecting the streaming subset isn't too hard.

Norm ponders the plausibility of using a regex

Henry: I think a regex could detect the the Schema subset

Norm objects to the idea of *requiring* a processor to support streaming

Norm proposes that we take the XPath 1/2/subset question to email

Any other business?

Alessandro: Did we have a conversation about setting up bugzilla

Norm: Yes

-> http://www.w3.org/Bugs/Public/

<Alessandro> Excellent

Norm will make the XPath question an issue as an example

Summary of Action Items

[NEW] ACTION: Norm to begin summarizing the points of consensus [recorded in http://www.w3.org/2006/04/06-xproc-minutes.html#action02]
[NEW] ACTION: Norm to get this into the CG calendar [recorded in http://www.w3.org/2006/04/06-xproc-minutes.html#action01]
[End of minutes]

Minutes formatted by David Booth's scribe.perl version 1.127 (CVS log)
$Date: 2006/04/13 16:10:34 $