14:56:14 RRSAgent has joined #xproc 14:56:14 logging to http://www.w3.org/2009/10/22-xproc-irc 14:56:16 Zakim, this will be xproc 14:56:16 ok, Norm; I see XML_PMWG()11:00AM scheduled to start in 4 minutes 14:56:19 Meeting: XML Processing Model WG 14:56:19 Date: 22 Oct 2009 14:56:19 Agenda: http://www.w3.org/XML/XProc/2009/10/15-agenda 14:56:19 Meeting: 157 14:56:19 Chair: Norm 14:56:20 Scribe: Norm 14:56:22 ScribeNick: Norm 14:57:02 XML_PMWG()11:00AM has now started 14:57:04 +Norm 15:00:38 +MoZ 15:00:41 -MoZ 15:00:43 +MoZ 15:01:25 zakim, please call ht-781 15:01:46 ok, ht; the call is being made 15:01:50 +Ht 15:02:52 +[ArborText] 15:07:33 Zakim, who's on the phone? 15:07:33 On the phone I see Norm, MoZ, Ht, PGrosso 15:07:41 Present: Norm, Mohamed, Henry, Paul 15:07:46 Topic: Accept this agenda? 15:07:46 -> http://www.w3.org/XML/XProc/2009/10/22-agenda 15:07:50 Accepted. 15:08:24 Norm: Can we talk about the meaning of an unavailable binding on p:with-option and p:with-param? 15:08:31 Topic: Accept minutes from the previous meeting? 15:08:31 -> http://www.w3.org/XML/XProc/2009/10/15-minutes 15:08:36 Accepted. 15:08:40 Topic: Next meeting: telcon 31 Oct 2009 15:08:50 s/31 Oct/29 Oct/ 15:09:00 Paul gives regrets. 15:09:28 Norm: Telcon of 5 November is cancelled. 15:09:55 Topic: Telcon facilities at TPAC 15:09:58 Norm: Confirmed. 15:10:21 Topic: XProc versioning proposals 15:10:51 -> http://lists.w3.org/Archives/Public/public-xml-processing-model-comments/2009Oct/0074.html 15:11:13 Norm summarizes 15:11:37 Vojtech has joined #xproc 15:13:27 +Vojtech 15:13:51 Present: Norm, Mohamed, Henry, Paul, Vojtech 15:13:57 -> http://lists.w3.org/Archives/Public/public-xml-processing-model-comments/2009Oct/0074.html 15:15:07 Norm: Three clearly open questions: where is @version allowed, does use-when count inside a p:inline, do we do any static analysis on p:when/p:try blocks when they contain invalid steps. 15:15:31 Norm: Any other questions or comments? 15:15:41 Vojtech: What about the importing of the standard step library. 15:16:07 Norm: I think we should not allow importing of declarations for the builtin steps. 15:16:10 Henry: I think that's right. 15:16:23 Henry: On a larger scale, I'm uncomfortable with the upward percolating invalid story. 15:16:38 ...I worry that it isn't complete or correct. I would like to identify that aspect of this proposal as a feature at risk. 15:16:54 ...so that we can jettison it without going back to last call again again if we remove it. 15:18:28 Norm: I'm perfectly happy to do that, but I can't think of any static meaning for a subpipeline with an invalid step that will absolutely be executed. 15:18:58 Henry: Right. I think use-when is the only thing that will work and I want to be able to jettison all the invalid stuff without going back to last call. 15:19:07 Vojtech: I agree with Henry, I thnk the results are going to be unpredictable. 15:19:10 s/thnk/think/ 15:19:35 Norm: Ok. I'm happy with that. Or we could just pull it all out now. 15:19:57 Vojtech: There's still this story about the unknown ports. You have steps that you recognize but they have unknown ports. 15:20:07 ...We could say you have to use use-when there, or we could keep the new story about defaults. 15:20:56 Henry: The motivation for doing our best here came from Jeni. 15:21:02 Norm: Jeni is happy with the proposal: http://twitter.com/JeniT/status/4898625357 15:21:29 More discussion. 15:22:51 Norm mumbles about some folks wanting to be able to use pipelines without changing them. 15:23:11 Norm uses the "messages" output port on p:xslt as an example. 15:23:40 Henry: That use case is interesting becauase it doesn't need a p:choose. You don't get the messages, but maybe you're willing to live with that. 15:23:54 ...I can just about see that. But I think as far as the steps I've never heard of story, that's never going to work. 15:23:59 ...There's never going to be a graceful fallback. 15:24:56 ...If we're not going to do the whole thing, I think the new ports case is worth keeping, but lose all the "upward percolation" of invalid p:* steps. 15:25:15 s/becauase/because/ 15:25:32 Vojtech: If the processor sees an unknown step from the p: namespace, I think you just can't know what it means. I would force the pipeline author to use use-when in that case. 15:25:47 ...But if the pipeline contains only known steps with new ports, then I think the simple defaulting story can be made to work there. 15:26:07 ...It's not hard to implement and it's predictable. 15:26:25 Norm: Does anyone want to argue for the more complicated story on this call right now. 15:28:45 Henry: I think the fact that you can't tell if the first child of a p:declare-step is a new step or some sort of new name for p:variable makes it very hard to decide what to do. 15:28:56 Vojtech: There may be unknown elements that effect the dependency graph. 15:29:40 Norm: Ok. I'm willing to concede that use-when and the more complicated invalidation store are two ways to do the same thing. 15:30:49 ...so maybe we should just do the simpler thing. You *have* to change the pipeline in some way, so you might as well change it in the way that's completely predictable. 15:31:22 Norm: So the proposal on the table now is the one I made, modified to remove the "upwards percolating" invalid story for unknown step types. 15:31:30 Vojtech: For unknown XProc elements. 15:31:48 Norm: Is anyone unhappy with that change? 15:32:25 Mohamed: I think I still have to go through. My former proposal was to try to get rid of use-when. My understanding is that use-when is pretty hard for users to understand. 15:32:49 ...So I think I just cannot agree without knowing what we're going to say about use-when. 15:33:03 Henry: In almost any case, the outcome of this discussion is going to be a new draft. 15:34:52 Mohamed: My idea is that the use-when should not be used everywhere. It should have another name. And it should only be used on when or try/catch. 15:35:04 ...A use-when is way more poweful than the problem we have to solve. 15:35:58 Norm: We could do that, but I'm not sure it's necessary. 15:37:11 Mohamed: I think we should just say that if the attribute "must-understand" is provided on p:when, then this branch shouldn't be analyzed in V.x. It's use-when but it's less powerful and solves just the use case we have. 15:38:02 Vojtech: One problem with this story is, suppose in V2 we introduce a new element for an option or something and that one you can't put in a p:choose. You can do that only with steps. 15:38:49 Henry: If we go back to the original observation that we're trying to handle the unexpected, a simple, general mechanism is probably the best approach. 15:39:28 ...The other thing is, there's a lot to be said for leveraging experts understanding of difficult material and use-when is already there. 15:39:57 Norm: I think that's a good point. 15:41:13 Vojtech: What I like about the use-when proposal is that it's something that will be valid in new versions. 15:41:46 ...We could ask on xproc-dev 15:43:05 Mohamed: I want to have an explicit mechanism, but I think use-when is a real nightmare for tools that help users build their pipeline. 15:43:47 Henry: I don't have much experience with use-when in XSLT, but the semantics seem quite clear to me. 15:44:01 ...It's the opposite of XInclude, "this tree isn't here." 15:44:26 ...I can see where some some complexity might arise in XSLT with templates and literal constructors, but we don't have that problem. 15:45:38 Mohamed: My problem is that we can make pipelines that will have completely different connections depending on the version of XProc that you're using: consider putting use-when on a p:pipe inside a p:source. 15:46:05 Norm: I think Mohamed's point is that you can nest two effectively completely different pipelines in the same file. 15:47:20 Vojtech: It's true that use-when is a tool for forwards-compatibility, but it's also a much more general tool: you can use it to make pipelines that are compatible across different implementatins. I don't know if that's good or bad. 15:48:39 Norm: I appreciate that Mohamed has reservations, but I don't hear consensus moving away from use-when on this call. 15:49:15 Norm: I'd like to say that the consensus of the wG seems to be that they want to see a draft with use-when, so let's try to move forward that way. 15:49:56 Norm: So let's close the open questions. Where is a version attribute allowed? 15:50:48 Norm: Proposal: On p:pipeline, p:library, and p:declare-step. No where else. And required on the document element of a pipeline document. 15:51:10 Norm: I can live with that. 15:51:20 Accepted. 15:51:30 Norm: Second question: what are the semantics of use-when inside a p:inline? 15:52:05 Norm: Proposal: it's treated just like any other attribute and has no special semantics. 15:52:55 Vojtech: So take the http-request step, suppose we add something to the c:request element. 15:53:10 Norm: You wouldn't be able to do that all in p:inline, you'd have to build it up in some explicit way. 15:53:36 Accepted. 15:54:02 Norm: We're throwing out the whole backwards-chaining invalidation story, so the last question no longer applies. 15:54:46 Vojtech: We already decided that importing the standard library is not allowed. 15:54:49 Norm: Yes 15:54:54 Norm: Anyone object to that? 15:54:56 None heard. 15:55:06 ACTION: Editor to write this up as a new draft. 15:55:51 Topic: Any other business? 15:56:31 None heard. 15:56:38 Adjourned. 15:56:39 -Ht 15:56:40 -Norm 15:56:40 -PGrosso 15:56:41 -Vojtech 15:56:45 -MoZ 15:56:46 XML_PMWG()11:00AM has ended 15:56:47 Attendees were Norm, MoZ, Ht, PGrosso, Vojtech 15:56:48 PGrosso has left #xproc 15:56:51 RRSAgent, set logs world-visible 15:56:56 RRSAgent, draft minutes 15:56:56 I have made the request to generate http://www.w3.org/2009/10/22-xproc-minutes.html Norm 17:13:57 Zakim has left #xproc