Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, November-11-2009 Attendees Suman Kalia (IBM) Steve Hanson (IBM) Mike Beckerle (Oco) Peter Lambros (IBM) Steve Marting (Progeny) Stephanie Fetzer (IBM) Apologies Alan Powell (IBM) 1. 051 Scoping Rules Two issues discussed: a) Use of selectors Reviewed Suman's selectors examples. Agreement that the semantic was correctly captured and no further action needed. b) Default dfdl:format annotation Rejected proposal to wrap this in an unnamed dfdl:defineFormat. All dfdl:definexxx should be named. Action 51 closed. 2. 061 Refactor dfdl:textNumberFormat to remove dfdl:numberBase. Reviewed Alan's updated spec fragment. Looks good, a couple of comments: a) Suggestion to replace the enum 'text' from dfdl:textNumber Representation, as it is confusing because of dfdl:representation enum 'text'. Proposals were 'plain' or 'regular'. More welcomed. b) In dfdl:textNumberFormatRef, the clause should just say "Only applies when textNumberBase is '10' " for consistency with other text properties. Action 61 updated. 3. 059: External specification of encoding, byte order Reviewed Steve H's proposal. Agreed that DFDL xsd wins over context. Agreed that $encoding & $byteOrder would be built-in 'external' variables in DFDL namespace. $encoding should have default UTF-8 $byteOrder should have default big-endian Rejected formal spec statement that DFDL implementation can optionally override DFDL xsd Action 59 updated. 4. 045 Resolving points of uncertainty and parsing rules Continued discussion of semantics of discriminators and arrays, using Mike's example. The example has 3 levels of uncertainty. The following key points emerged during the web meeting. The use of timing="after" on a 'forward looking' dfdl:discriminator does not always work. Because it is evaluated at the end of parsing the hosting component, a failure might have occurred while parsing one of the children. The failure will cause backtracking, even though we might have parsed enough to evaluate the discriminator. The WTX equivalent (component rules on identifier fields) handles 'forward looking' by continually trying to evaluate the rule as it processes a component's children. Conceptually timing="during". Mike changed the discriminators so that they were decorated, eg, choiceDiscriminator, occurDiscriminator. This makes what the discriminator applies to more obvious. An equivalent alternative is to link the component and the discriminator using an id/idref, or an SCD. Mike will think more on this, and also whether other decorated discriminators are needed, eg, for unordered/floating sequences. Stephanie will supply equivalent WTX type tree for comparison. It was noted that there is a big semantic difference between DFDL discriminators and WTX component rules - if the former's expression evaluates to false then a processing error is raised. Not so with WTX, which will continue on. Action 45 updated. Action 33 closed and merged into 45. 5. Actions Updated below. Note closure of action 62 which was not discussed on the call - we have the name of an IBM technical writer to assist with spec completion. Next call 18 November 13:00 UK Meeting closed, 15:00 Next action: 064 Actions raised at this meeting No Action Current Actions: No Action 012 AP/SH: Update decimalCalendarScheme 10/9: Not allocated yet 17/9: No update 24/9: Add calendar binary formats to actions 22/10: No progress 16/1: proposal distributed and discussed. Will be redistributed 21/1: add locale, 04/02: changed from locale to specific properties 18/2: Need more investigation of ICU strict/lax behaviour. 08/04: Not discussed 22/04: AP to complete asap once the ICU strict/lax behaviour is understood. 29/04: No progress 06/05: No progress 13/05: Calendar has been added to latest spec version v034 but still a few details to clarify. 20/05: No Progress ... 09/06: No Progress (low priority) 17/06: SH to check ICU code for lax calendar behaviour 24/06: no progress ... 12/08: no progress 19/08: Inconsistencies are being found in ICU behaviour so Calendars need reviewing again. 26/08: Specific three character short time zones may not be maintained during round tripping when there is more than one short form for a time zone offset. Because dates and datetimes in the infoset only maintain a time zone offset so on unparsing it isn't possible to say which short form will be selected for a particular offset when there is more than one possible. Need to document. 09/09: no progress ... 14/10: no progress 21/10: Will produce a list of known issues. 28/10: Discussed ICU farctional seconds behaviour. SF to send latest understanding. 04/11: no progress 11/11: no update 037 All: Approach for XML Schema 1.0 UPA checks. 22/04: Several non-XML models, when expressed in their most obvious DFDL Schema form, would fail XML Schema 1.0 Unique Particle Attribution checks that police model ambiguity. And even re-jigging the model sometimes fails to fix this. Note this is equally applicable to XMl Schema 1.1 and 1.0. While the DFDL parser/unparser can happily resolve the ambiguities, the issue is one of definition. If an XSD editor that implements UPA checks is used to create DFDL Schema, then errors will be flagged. DFDL may have to adopt the position that: a)DFDL parser/unparser will not implement some/all UPA checks (exact checks tbd) b) XML Schema editors that implement UPA checks will not be suitable for all DFDL models c) If DFDL annotations are removed, the resulting pure XSD will not always be valid (ie, the equivalent XML is ambiguous and can't be modelled by XML Schema 1.0) Ongoing in case another solution can be found. 29/04: Will ask DG and S Gao for opinion before closing 06/05: Discussed S Gao email and suggestions. Decided need to review all XML UPA rules and decide which apply to dfdl. 20/05: SH or SKK to investigate 27/05: No Progress 03/06: The concern is that some dfdl schemas will fail UPA check when validation is turned on or when editted using tooling that enforces UPA checks. Renaming fields will resolve some/most issues. Need documentation that describes issue and best practice. 17/06: no change 24/06: no change 01/07: no progress ... 12/08: No Progress (lower priority) 19/08: Clarify that this action is to go through the XML UPA checks to assess impact on dfdl schemas and advice best practice. Name clashes is just one example. SH or SKK 26/08: No Progress (lower priority) 09/09: no progress ... 04/11: no progress 11/11: Steve has started to look at this. He has requested a 'consumable' definition of the UPA rules from the XSD WG members. Even non-normative Appendix H in the XSD 1.0 spec is hard to consume. 045 20/05 AP: Speculative Parsing 27/05: Psuedo code has been circulated. Review for next call 03/06: Comments received and will be incorporated 09/06: Progress but not discussed 17/06: Discussed briefly 24/06: No Progress 01/07: No Progress 15/07: No progress. MB not happy with the way the algorithm is documented, need to find a better way. 29/07: No Progress 05/08: No Progress. Will document behaviour as a set of rules. 12/08: No Progress ... 16/09: no progress 30/09: AP distributed proposal and others commented. Brief discussion AP to incorporate update and reissue 07/10: Updated proposal was discussed.Comments will be incorporated into the next version. 14/10: Alan to update proposal to include array scenario where minOccurs > 0 21/10: Updated proposal reviewed 28/10: Updated proposal reviewed see minutes 04/11: Discussed semantics of disciminators on arrays. MB to produce examples 11/11: Absorbing action 033 into 045. Maybe decorated discrminator kinds are needed after all. MB and SF to continue with examples. 049 20/05 AP Built-in specification description and schemas 03/06: not discussed 24/06: No Progress 24/06: No Progress (hope to get these from test cases) 15/07: No progress. Once available, the examples in the spec should use the dfdl:defineFormat annotations they provide. ... 14/10: no progress 21/10: Discussed the real need for this being in the specification. It seemed that the main value is it define a schema location for downloading 'known' defaults from the web. 28/10: no progress 04/11: no progress 11/11: no update 056 MB Resolve lengthUnits=bits including fillbytes 12/08: No Progress ... 28/10: no progress 04/11: MB to look at lengthUnits = bits 11/11: no update 059 9/9: SH Define how encoding, byteorder and floating point format externally 16/09: no progress 07/10: no progress 14/10: no progress 21/10: SH to investigate 28/10: no progress 04/11: no progress 11/11: SH proposal accepted. One open issue - what is the full list of built-in variables? 061 AP Refactor dfdl:textNumberFormat to remove dfdl:numberBase. 14/10: Base 2, 8, 16 numbers are invariably integers without formatting, use of pattern etc is overkill 21/10: no progress 28/10: no progress 04/11: no progress 11/11: Reviewed AP proposal, some comments to incorporate. 063 Write DFDL primer and test cases. 11/11: no update Closed actions No Action 033 MB: Need for scope indicator on discriminator 08/04: In progress within IBM 22/04: Waiting for TK to return from leave to complete. 29/04: TK has sent examples shown need for discriminators beyond choice. Agreed. MB to respond to TK 06/05: Discussed suggestion of adding type indicator to discriminator. MB to provide examples. 15/03: Semantic documented in v034. MB to provide examples of need for scope indicator on discriminator 20/05: MB to provide examples of need for scope indicator on discriminator (but lower priority than action 029) 27/05: No Progress (lower priority) .... 07/10: no progress 14/10: Action re-titled and assigned to Mike B 21/10: no progress 28/10: no progress 04/11: Mike to produce examples for choices with variable occurrence arrays. 11/11: Closed. Incorporated into action 045. 051 Scoping rules. MB: to document change to scoping rules to satisfy implementation concerns 17/06: MB and SH proposals discussed. Needs further discussion 24/06: AP to update presentation with latest proosal 24/06: AP had updated presentation. MB to review 08/07: Discussed at length. Simple types will now take annotations. Variables will be used for parameters. 15/07: No further progress. Needs final write up. 29/07: No Progress 05/08: No Progress 12/08: No Progress 19/08: AP will document new syntax rules. 26/08: No Progress 09/09: AP has documented new scoping rules. Not discussed 16/09: Not disussed. AP to update element reference examples 30/09: Significant dissatisfaction with proposed new rules. New proposal developed during call. AP to document. 07/10: New proposal was refined. Details in minutes. 14/10: Discussed at length. Details in minutes. 21/10: Discussed at length. Details in minutes. 04/11: defineFormat can only contain one active format block, Drop baseFormat, SKK to produce examples for selectors. 04/11: Further discussion see minutes. SKK to produce examples of selectors. 11/11: Closed. No open questions. Incorporate into spec via work item 051. 062 SH investigate technical writer support. 28/10: SH had contacted S Gao to understand the W3 process and support. 04/11: no progress 11/11: Closed. SH has the name of an IBM technical writer who can help with spec preparation - Mark Tibbits. Work items: No Item target version status 005 Improvements on property descriptions not started 011 How speculative parsing works (combining choice and variable-occurence - currently these are separate) (from action 045) awaiting completion of actions 045 012 Reordering the properties discussion: move representation earlier, improve flow of topics not started 033 Numeric data - what physical reps are allowed for what logical types (from action 020) 037 ensure all behaviour documented 036 Update dfdl schema with change properties ongoing 038 Improve length section including bit handling some improvement in 036 042 Mapping of the DFDL infoset to XDM none not required for V1 specification 051 Revised scoping rules (from action 051) 037 058 textPadCharacter %#rxx limitation and split to textxxxxPadCharacter 037 059 limit terminatorCanBeMissing to last element in schema. Ignore elsewhere. 037 060 New empty string semantic for dfdl:binaryBooleanTrueRep 037 061 Change maxOccurs violations from processing error to validation error (if not 'fixed') 037 062 Drop calendarUseZForUTC. describe zU, IU and TU symbols 037 063 DefineFormat can contain only one active format. Drop baseFormat 037 Alan Powell MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England Notes Id: Alan Powell/UK/IBM email: alan_powell@uk.ibm.com Tel: +44 (0)1962 815073 Fax: +44 (0)1962 816898 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