From Tim: I remembered the reason why I thought this was a good idea. Consider the situation where someone is generating their DFDL schema from
From Tim: I remembered the reason why I thought this was a good idea. Consider the situation where someone is generating their DFDL schema from
From Tim: I remembered the reason why I thought this was a good idea. Consider the situation where someone is generating their DFDL schema from
Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, August 04-2010 Attendees Steve Hanson (IBM) Alan Powell (IBM) Stephanie Fetzer (IBM) Ella Belisario (IBM) Apologies Mike Beckerle (Oco) Suman Kalia (IBM) Tim Kimber(IBM) 1. Current Actions Updated Below 2. dfdl:hidden There has been some discussion on whether the 'hidden' global group should be indicated in some way. Option A: Leave the DFDL specification unchanged, in which case we must expose the internal DFDL constructs to the user of the DFDL editor. That means the following: - to make a group member hidden, a local group and a global group must be created to represent the hidden item. This is a refactoring operation. - to make the UI consistent, the global group needs to be exposed as a first-class modelling construct. That means that it appears along with local element/element ref/local group/group ref in any context where the user is dealing with group members. There are more details of what the editor needs to do in Steve's comments on the first note in this chain. Option B: Make one change to the DFDL specification, to make it possible for a DFDL editor to present dfdl:hidden as a simple flag on any group member The change is to put a DFDL annotation on the global sequence group that contains the hidden items. This would allow the DFDL editor to distinguish these global groups from the real ones that belong to the user's schema. This allows a hidden item to be represented by a pair of *internal* groups, both of which have a dfdl:annotation. One is local, and appears where the hidden item used to appear, The other is global and is referenced by the local one. They are created and deleted as pairs whenever an item is hidden or un-hidden. A lively discussion. The specification works as currently defined so discussed whether changes need to be made to make tooling easier. There shouldn't be 'conventions' in particular tooling as they must be able to properly deal with schema from other tools that would not obey those conventions. Steve stated that it is often dangerous to hide too much from users when they can see they underlying schema. To be continued. 3. dfdl:discriminator : the 'message' attribute meta-data. The model is large, and consists of many references to global structures. Each global structure ( e.g. an HL7 segment ) is identified in a particular way. Sometimes the segment is required, sometimes it is not. Sometimes it occurs as a child of a choice group, and sometimes not. Regardless, it is highly likely that the segment will be identified in the same way wherever it occurs. A natural decision for the modeler would be to create a dfdl:discriminator on all references to the segement, even if the ref is not under a point of uncertainty. It's harmless, and it carries no performance penalty. If we disallow the "message" attribute, it will force the modeler to put in extra logic to work out whether the ref is under a POI, and generate an assert/discriminator as appropriate. I'd be interested to know what Steph thinks about this - I think I've heard her say that she sometimes uses discriminators where an assert would have done the job, just to maintain consistency throughout the model. 04/08: not discussed. Meeting closed, 16:00 Next call Wednesday 11 August 2010 15:00 UK (10:00 ET) Next action: 110 Actions raised at this meeting No Action 108 dfdl:hidden There has been some discussion on whether the 'hidden' global group should be indicated in some way. 04/08: A lively discussion. The specification is works as currently defined so whether changes need to be made to make tooling easier. There shouldn't be 'conventions' in particular tooling as they must be able to properly deal with schema from other tools that would not obey those conventions. Steve stated that it is often dangerous to hide too much from users when they can see they underlying schema. To be continued. 109 dfdl:discriminator : the 'message' attribute meta-data. The model is large, and consists of many references to global structures. Each global structure ( e.g. an HL7 segment ) is identified in a particular way. Sometimes the segment is required, sometimes it is not. Sometimes it occurs as a child of a choice group, and sometimes not. Regardless, it is highly likely that the segment will be identified in the same way wherever it occurs. A natural decision for the modeler would be to create a dfdl:discriminator on all references to the segement, even if the ref is not under a point of uncertainty. It's harmless, and it carries no performance penalty. If we disallow the "message" attribute, it will force the modeler to put in extra logic to work out whether the ref is under a POI, and generate an assert/discriminator as appropriate. I'd be interested to know what Steph thinks about this - I think I've heard her say that she sometimes uses discriminators where an assert would have done the job, just to maintain consistency throughout the model. 04/08: not discussed. Current Actions: No Action 066 Investigate format for defining test cases 25/11:IBM to see if it is possible to publish its test case format. 04/12: no update ... 17/02: IBM is willing in principle to publish the test case format and some of the test cases. May need some time to build a 'compliance suite' 24/03: No progress 03/03: Discussions have been taking place on the subset of tests that will be provided. 10/03: work is progressing 17/03: work is progressing 31/03: work is progressing 14/04: And XML test case format has been defined and is being tested. 21/04. Schema for TDML defined. Need to define how this and the test cases will be made public 05/05: Work still progressing 12/05: Work still progressing 02/06: Work still progressing on technical and legal considerations ... 21/07: work continues 04/08: work continues 085 ALL: publicize Public comments phase to ensure a good review.. 14/04: see minutes 21/04: Press release, OMG and other standards bodies. 05/05: Alan and Steve H have contacted other standards bodies. Will ask them to add comments on spec 15/05: still no public comments 02/06: No public comments 16/06: Public comments period has ended with no external comments. Alan had posted changes made in draft 041. Steve suggested send a note to the WG highlighting these changes. Steve also suggested requesting an extension as other IBM groups may review. We discussed whether this was necessary as changes will need to be made during the implementation phase anyway. Alan to ask OGF what the process is for changes post public comment. 23/06: Still no comments. Alan will contact OGF to understand the rest of the process. 30/06: Alan has emailed Joel asking what the process is now public comment period is over andcan we update the published version with WG updates. No response yet. 07/07: No response. Alan will chase up 14/07: No response from Joel. Sent email to Greg Newby by no response. 21/07: Still no response. 04/08: Joel has responded that it is up to the WG to decide if the changes are significant enough to need additional review. Alan to contact David Martin and Erwin Laure for guidance if we split the specification. 099 Splitting the specification in simpler sections. 07/07: Steve sent a proposal but not discussed. Alan will arrange a separate call. 14/07:Discussed Steve's proposal and Suman's and Alan's comments. Need to add choice, validation, facets. Also how does an implementation declare which subsets it supports. Suggested levels and/or profiles. Steve highlighted a problem when a DFDL schema from an implementation of just the core functions was moved to a full DFDL implementation what should happen about the missing properties. Does the full implementation need to be aware of subsets of functions? Should it raise a schema definition error for use of a function not in the subset. 21/07: no progress 04/08: Steve had updated proposed groups of function. (Subset_proposal_v2.ppt). We discussed whether its is better to have discrete sets of functions or expanding levels of function. Purpose of subsetting is: 1. Allow simpler implementations. (main purpose) 2. Simplify tooling 3. Simplify specification. Steve to contact previous members of WG to check if we have the correct subsets. 101 Semantics of 'fixed' 21/07: Discussed whether not matching the 'fixed' value should be a validation error or processing error. Decided that for consistency it should be a validation error. It would be useful however to avoid having to duplication of facet information in an assert which could become unwieldy for, say, a large enumeration. Suggestions - a parser option that 'converted all validation errors to porcessing errors' - a dfdl expression function that 'applied all facets' or 'applied specific facet' to a particular element. Stephanie will produce some examples of how this could be used.. 04/08: Stephanie had produced examples but they were not discussed due to lack of time 104 Expressions Discuss error behaviour when evaluating an expression in various contexts - All properties: wrong type returned : schema definition error exception when evaluating expression : schema definition error referenced variables/paths not available : schema definition error - Properties which allow a forward reference referenced variables/paths not available : no error. DFDL processor continues processing until the expression result is available, then acts on the result. 21/07: Steve stated the current definition that returning the incorrect type was a schema definition error and everything else was a processing error. 04/08: Not discussed 107 teston/testoff dfdl expression functions. Are these functions still needed. They were introduced to allow individual bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that use existence flags to see if they are still required. 04/08: Not discussed 108 dfdl:hidden There has been some discussion on whether the 'hidden' global group should be indicated in some way. 04/08: A lively discussion. The specification is works as currently defined so whether changes need to be made to make tooling easier. There shouldn't be 'conventions' in particular tooling as they must be able to properly deal with schema from other tools that would not obey those conventions. Steve stated that it is often dangerous to hide too much from users when they can see they underlying schema. To be continued. 109 dfdl:discriminator : the 'message' attribute meta-data. The model is large, and consists of many references to global structures. Each global structure ( e.g. an HL7 segment ) is identified in a particular way. Sometimes the segment is required, sometimes it is not. Sometimes it occurs as a child of a choice group, and sometimes not. Regardless, it is highly likely that the segment will be identified in the same way wherever it occurs. A natural decision for the modeler would be to create a dfdl:discriminator on all references to the segement, even if the ref is not under a point of uncertainty. It's harmless, and it carries no performance penalty. If we disallow the "message" attribute, it will force the modeler to put in extra logic to work out whether the ref is under a POI, and generate an assert/discriminator as appropriate. I'd be interested to know what Steph thinks about this - I think I've heard her say that she sometimes uses discriminators where an assert would have done the job, just to maintain consistency throughout the model. 04/08: not discussed. Closed actions No Action 086 AP: Nils and Defaults during unparsing - update table 31/03: TK to documetn use cases for parsing 14/04: Investigate new property to control empty string behaviour. 21/04: After investigation a new property is not required. New rules developed and tables updated. Need examples of complexTypes to confirm tables apply. Review Nils, defaulting spec section. 05/05: Discussed defaulting complex elements. Tables updated but need to add terminator. SH; to confirm WMD behaviour when infoset item has no value on unparsing Need to describe defaulting choices. 15/05: More discussion. Alan updating sections 26/05: Discussed draft updates. Stephanie to confirm asserts do not make an element required. Alan will update draft.. All: review rest of draft. 02/06: Alan updated description. Please review. Discussed Stephanie's example using discriminators. Decided no changes needed. 16/05: went through Steves comments. Steve to update draft. 23/06: Steve's updates to the rules discussed. See minutes. Rest of document needs updating. 30/06: Discussed Alans updates. Some corrections. Alan will send out updated copy for review before next call. 07/07: Discussed Alan updates and Tim and Steve's comments. Still some corrections and updates. 14/07: Discussed Alan updates (v9) Still some corrections and updates. 21/07: Discussed Draft 10. Shouldn't mention input/outputValueCalc in this section. Mention defaulting in calculated values section. Move details of nilValue from nilKind property. 04/08: Draft v11.1 was included in Spec Draft v42. Minor corrections. Closed. 102 Clarify the specification of error reporting from a DFDL processor - section 2.3 needs to be updated 21/07: Section is not clear. Alan will update. 04/08: Sections updated in draft 42. Closed 103 Asserts and discriminators - specify the scope of forward references. Must be downward-only. The expression must be resolvable by the time the component on which it is positioned goes out of scope - otherwise it is a processing error. 21/07: Agreed 04/08: Updated in draft 42. Closed Work items: No Item target version status 005 Improvements on property descriptions not started 012 Reordering the properties discussion: move representation earlier, improve flow of topics not started 036 Update dfdl schema with change properties ongoing 042 Mapping of the DFDL infoset to XDM none not required for V1 specification 070 Write DFDL primer 071 Write test cases. 083 Implement RFC2116 Regards Alan Powell Development - MQSeries, Message Broker, ESB IBM Software Group, Application and Integration Middleware Software ------------------------------------------------------------------------------------------------------------------------------------------- IBM MP211, Hursley Park Hursley, SO21 2JN United Kingdom Phone: +44-1962-815073 e-mail: alan_powell@uk.ibm.com Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU