November 2009 - dfdl-wg - lists.ogf.org

postfix separators, terminators, finalTerminatorCanBeMissing
by Tim Kimber 20 Nov '09

20 Nov '09

I would like to explore the semantics of separators and terminators, and raise a question about consistency with regard to toleration of missing separators/terminators. Sorry for the barrage of questions lately - the implementation is uncovering some new angles. Relevant snippets from v0.36 of spec: Section 14.2 Text Markup The terminator region contains the terminator string. When a terminator is expected it is a processing error if one of the values is not found. However, if dfdl:finalTerminatorCanBeMissing is specified then it is not an error if the terminator is not found. ... When the finalTerminatorCanBeMissing property is true, then when an element is the last element in a sequence or array, then on input, it is not a parse error if the terminator is not found but end-of-parent or an enclosing delimiter is encountered instead. Section 17.3 Sequence groups with delimiters The separator region contains one of the strings specified by the dfdl:separator property. When this property has "" (empty string) as its value then the separator region is of length zero. ... ‘postfix’ means the separator occurs after each element. On parsing the separator after the last item is optional. On unparsing the final separator will always be written. Section 17.3.1 Sequence groups and separators re: ordered/suppressAtEnd : All separators must be found in the data except that when the sequence has trailing optional items, the separators are suppressed for any final missing items. My interpretation of the spec: a) If an element's parent group defines a separator, that separator might not appear after the element. Instead, the group might be terminated early by the group's own terminator, or by the separator/terminator of an enclosing element/group or by end-of-data. b) On the other hand, if an element defines a terminator, that terminator *must* appear after the element unless FTCBM="true" ( in which case the element and its parent group can be terminated early by enclosing markup or end of data ) c) separatorPosition="postfix" is not enforced rigidly. The input document can always be constructed as if separatorPosition="infix" and the parser will not complain. This allows early termination of a separated group by enclosing markup, as well as by end-of-data. d) The FTCBM flag allows the terminator of the final group member to be missing. This allows early termination of the group by enclosing markup or by end-of-data. I have reservations about these rules. - It seems overly lax to unconditionally allow 'postfix' to behave like 'infix'. The equivalent flexibility for a terminator requires FTCBM to be set to "true". - FTCBM is not as useful as it seems because it only applies to the final group member. If the final group member is optional, the user will be forced to use a postfix separator, and will then lose the control afforded by FTCBM. - DFDL needs to allow strict validation of postfix separators/terminators. I can't see a way to achieve that with the current rules ( see example below) Example: Lines are separated by <lf>. Lines have up to 3 fields. Fields can be empty. Fields are always terminated by a *. line:field1*field2*field3*<lf> line:field1*field2*<lf> line:field1**field3*<lf> With the current rules, this form of the second line line:field1*field2<lf> ...would also be allowed: ( assuming that the * is defined as a postfix separator with separatorPolicy="suppressAtEnd" ) Note that the missing * after field2 is silently tolerated because postfix separators are allowed to be omitted. To enforce the presence of the * after field2 it would have to be defined as a terminator on every field. But that would remove the flexibility afforded by the use of separators ( see third line ) A possible solution: - Strictly enforce separatorPosition="postfix". - Make terminators mandatory - Remove the FTCBM flag, and replace it with a flag which tolerates end-of-data where any separator/terminator was expected. The definition of end-of-data would include the end of a defined-length parent element, but would specifically exclude end-of-parent caused by enclosing markup ( because that would re-introduce the ambiguity which I'm trying to avoid ). These rules are considerably tighter than the existing ones, but I don't think they make anything impossible. I do think they make the meaning of the various settings a lot simpler. Terminators would be less 'optional' than before, but I suspect that the real-world scenarios would be catered for. Anyway - comments invited. ( invitation unnecessary, I suspect ) regards, Tim Kimber, Common Transformation Team, Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 246742 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

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Minutes for OGF DFDL Working Group Call, November-18-2009
by Alan Powell 19 Nov '09

19 Nov '09

Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, November-18-2009 Attendees Suman Kalia (IBM) Steve Hanson (IBM) Mike Beckerle (Oco) Alan Powell (IBM) Steve Marting (Progeny) Stephanie Fetzer (IBM) Tim Kimber(IBM) Apologies Peter Lambros (IBM) 1.051 Scoping Rules Reviewed of draft 8. Comments made by Suman and Stephanie will be incorporated. Action Closed 2.061 Refactor dfdl:textNumberFormat to remove dfdl:numberBase. Reviewed updated spec fragment and approved. Action Closed 3.059: External specification of encoding, byte order This was largely agreed on last week's call but additional discussion about whether additional properties should have predefined variables. Agreed to add dfdl:binaryFloatRepresentation and dfdl:OutputNewLine. Action closed 4.045 Resolving points of uncertainty - Disciminators Continue discussion of semantics of discriminators and arrays Stephanie took us through Mike's example implemented in WTX and number of points emerged. WTX discriminators (component rules) only resolve an immediate parent. If one instance on an array is found then the array is said to be found even if minOccurs are not found. An explicit discriminator would be needed to enforce minOccurs. There was also a discussion of the forward referencing permitted which is only to children. SF agreed to get documentation about WTX discrimination. 5.045 Resolving points of uncertainty - parsing rules Tim and Alan had sent emails about the rules for scanning or skipping of text fields during parsing. Tim pointed out there there was not way to force skipping of text fields and it was agreed that this was an omission. Tim suggested that lengthKind should be used to specify whether to scan or skip and that dfdl:length shuold be examined when lengthKind=delimited to decide if it is a fixed/known length delimited field. There was not agreement and we ran out of time. To be continued. Action 65 raised 8.OGF28 Call for papers Mike and/or Steve will make a request to a WG presentation Meeting closed, 15:10 Next call 25 November 13:00 UK Next action: 066 Actions raised at this meeting No Action 064 MB/SH Request WG presentation at OGF 28 065 Resolve parsing rules for various lengthKinds 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 18/11: 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. 18/11: no update 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. 18/11: Went through WTX implementation of example. SF to gather more documentation about WTX discriminator rules. 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 18/11: 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 18/11: 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? 18/11: added dfdl:binaryFloatRepresentation and dfdl:OutputNewLine. Action Closed 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. 18/11: Approved latest draft subject to minor comments from SF and SKK. Closed 063 Write DFDL primer and test cases. 11/11: no update 064 MB/SH Request WG presentation at OGF 28 065 Resolve parsing rules for various lengthKinds Closed actions No Action 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. 18/11: Approved draft 8 059 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? 18/11: added dfdl:binaryFloatRepresentation and dfdl:OutputNewLine. Action Closed - work item 064 061 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. 18/11: Approved latest draft subject to minor comments from SF and SKK. Closed - workitem 065 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 037 064 Define how encoding, byteorder and floating point format externally 037 065 Refactor dfdl:textNumberFormat to remove dfdl:numberBase. 037 066 document scope of selectors 037 Alan Powell MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England Notes Id: Alan Powell/UK/IBM email: alan_powell(a)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

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discriminator examples for discussion
by Mike Beckerle 18 Nov '09

18 Nov '09

Attached are two files. One is a DFDL schema that uses discriminators. The other is a test case file. I'd like to review the issues with discriminators on our call tomorrow by walking through these examples. To do this we will absolutely have to have screen sharing going on so I can point at things. So I have setup a "gotomeeting" which is a low impact web screen sharing thingy. If you've not used gotomeeting before, there is a brief download required, so you might want to get this out of the way before our call. https://www2.gotomeeting.com/join/319038563 Meeting ID: 319-038-563

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Agenda for OGF DFDL WG call 18 November 2009 - 13:00 UK (8:00 ET)
by Alan Powell 17 Nov '09

17 Nov '09

051 Scoping Rules Quick review of draft 8 (see e-mail) 061 Refactor dfdl:textNumberFormat to remove dfdl:numberBase. Review Alan's updated spec fragment (see e-mail) 059: External specification of encoding, byte order Update from Steve 045 Resolving points of uncertainty - Disciminators Continue discussion of semantics of discriminators and arrays 045 Resolving points of uncertainty - parsing rules Discuss emails from Tim and Alan Go through remaining actions Test suite for DFDL Discuss Mike's e-mail and what IBM is doing as part of its implementation work OGF28 Call for papers Plan to finish DFDL v1 How to track spec issues. Updated straw man schedule Activity Schedule Who Resolve Action items - 23 Nov 2009 WG Write up work items 16 Nov - 4 Dec 2009 AP Restructure and complete specification 23 Nov - 4 Dec 2009 AP WG review 7 Dec - 18 Dec 2009 WG Incorporate review comments 4 Jan - 29 Jan 2010 AP + OGF Editor Review / Incorporate changes 1 Feb - 1 Mar 2010 OGF OGF Public Comment period (60 days) 1 Mar - 30 Apr 2010 OGF OGF 28 Munich 15-19 March 2010 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 Alan Powell MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England Notes Id: Alan Powell/UK/IBM email: alan_powell(a)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

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How to determine the length of an element which has text representation
by Tim Kimber 17 Nov '09

17 Nov '09

The current version of the specification ( v0.36) does not clearly specify how an element which has a specified length should be parsed. - Section 14.3, when describing dfd:length says "Only used when lengthKind is ’explicit’ " - The precedence rules say that when lengthKind="delimited", no other properties are consulted - Section 17.3.2 has a comment saying that it is incorrect. The comment contains a couple of rather ambiguous statements about what the behaviour should be. Alan proposes that the behaviour should be as follows: - When dfdlLength has a value, the length of the field must always conform to that value. - When there is terminating markup in scope ( terminators or separators ) the parser always uses them. - If a text field has a defined dfdl:length AND there is terminating markup in scope, then the parser should first scan to find the actual length, then check the actual length against dfdl:length and raise a processing error if they do not match. I favour the following alternative rules - dfdl:lengthKind always determines the method that the parser will use to the find the length of the element - if lengthKind='explicit' or 'implicit' or 'prefixed' then the length is extracted without scanning. - if lengthKind='delimited' then the length is extracted by scanning and no check is performed against dfdl:length The alternative rules have the following advantages: - they provide a way of switching off scanning within the scope of a delimited structure. The proposed rules do not. - they are easier to implement ( parser doesn't have to keep track of whether there is any terminating markup in scope - lengthKind always provides the rule ) - they are slightly easier to explain to users for the same reason They do have the following drawbacks: - dfdl:length is completely ignored when lengthKind='delimited'. It is not even used to validate the extracted length. Some users might not like this. - there are known scenarios ( e.g. SWIFT 52B ) where it is necessary to check the length of a delimited field in order to choose the correct branch of a choice. Checking dfdl:length would make it easy to do that. re: the ignoring of dfdl:length, we *could* make a rule that the length is checked after the delimited scan has been performed. But then it would be necessary to ensure that dfdl:length was un-set for the far more usual case where the length is not important. I think the control of backtracking in the 52B scenario is an edge case. In most cases where delimited fields have a known length we can safely leave the length checking to the schema validator, or perhaps to a more functional complex validation layer. For 52B, the user will have to create a dfdl:assert to trigger the required processing error when the length is incorect. regards, Tim Kimber, Common Transformation Team, Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 246742 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

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Action 061 Refactor dfdl:textNumberFormat to remove dfdl:numberBase.
by Alan Powell 13 Nov '09

13 Nov '09

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. Updates made 'text' becomes 'standard' Alan Powell MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England Notes Id: Alan Powell/UK/IBM email: alan_powell(a)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

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Scoping V8
by Alan Powell 13 Nov '09

13 Nov '09

Although the scoping action was closed on the last call some updates to the proposal were needed after the discussion between Steve and I . The main update is to change the emphasis from scoping annotations to scoping 'representation properties'. This is because 1) the non-representation properties (ref and selector) are not defaulted or combined and 2) the same property may come from different annotations. I have also clarified the scoping of refs to escapeSchemes etc. Alan Powell MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England Notes Id: Alan Powell/UK/IBM email: alan_powell(a)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

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Minutes for OGF DFDL Working Group Call, November-11-2009
by Alan Powell 12 Nov '09

12 Nov '09

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(a)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

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Re: [DFDL-WG] Action 059: External specification of encoding, byte order
by Steve Hanson 12 Nov '09

12 Nov '09

As discussed on the call: For case 1) the DFDL xsd always wins, and the context is ignored. If the user wants to use the encoding/byte order from the context, then he must be explicit about this and use case 2) above Will adopt suggestion a). One question - are there any other DFDL properties like dfdl:encoding and dfdl:byteOrder that are commonly provided by context? How about dfdl:binaryFloatRepresentation, or dfdl:outputNewLine? Will not adopt suggestion b). Regards Steve Hanson Programming Model Architect, WebSphere Message Brokers, OGF DFDL WG Co-Chair, Hursley, UK, Internet: smh(a)uk.ibm.com, Phone (+44)/(0) 1962-815848 From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org Date: 05/11/2009 14:30 Subject: Action 059: External specification of encoding, byte order DFDL schemas can either: 1) specify fixed encoding(s)/byte order(s) for the data being described, 2) specify that the encoding/byte order is provided by the 'context' that invokes the DFDL processor (using the dfdl:defineVariable 'external' facility). ** For case 1), DFDL is faced with a problem. Namely what happens when the 'context' provides an encoding/byte order for the data, but the DFDL xsd specifies a different encoding/byte order. I think DFDL must make a statement about this situation, as there are several common scenarios where this could occur (HTTP, MIME, MQ). It is worth looking at the precedent set by XML in this regards. The analogous problem for XML is where the XML document itself specifies a different encoding (using the ?xml declaration) to the context. The recommendations for XML are stated in the appendix below - there is no universal rule. It is more complicated with DFDL though. A DFDL xsd can set up the encoding(s)/byte order(s) to use in several different places. Which of those would the context override? All of them? Just the one associated with the top-level structure? My conclusion is therefore that for case 1) the DFDL xsd always wins, and the context is ignored. If the user wants to use the encoding/byte order from the context, then he must be explicit about this and use case 2) above. There are two things that we could allow to be a bit more flexible: a) Pre-define $encoding and $byteOrder variables in the DFDL namespace. These would implictly have 'external' = 'true' and perhaps a 'defaultValue' as well. This simplifies the coding of a DFDL xsd for case 2). b) State that it is an implementation decision to provide an option to use a context encoding/byte order for case 1) instead of the ones in the DFDL xsd. In such a case, the context MUST override all encodings/byte orders in the system of xsds used by the DFDL processor. (In practice this is invariably a single encoding/byte order). . ** (Might be more than encoding & byte order - for example MQ also allows float format to be provided by context) Appendix: XML The equivalent situation for XML is where the XML document specifies its own encoding via the ?xml declaration, and the context also provides the encoding. There is no single rule, in summary: - Basicaly if there is a higher level protocol, then that defines the rules. - Eg, for MIME content-type text/xml, the context encoding is used. If this is omitted, the xml is assumed to be US-ASCII. The ?xml declaration encoding is not used. - Eg, for MIME content-type application/xml, the context encoding is used If this is omitted, the ?xml declaration encoding is used. - For files (where there is no context encoding) use of the ?xml declaration encoding is recommended. Note that in Message Broker, we always use the context encoding, as it should always be present. We never use the ?xml declaration. W3C XML 1.0 spec section F.2 Priorities in the Presence of External Encoding Information The second possible case occurs when the XML entity is accompanied by encoding information, as in some file systems and some network protocols. When multiple sources of information are available, their relative priority and the preferred method of handling conflict should be specified as part of the higher-level protocol used to deliver XML. In particular, please refer to [IETF RFC 3023] or its successor, which defines the text/xml and application/xml MIME types and provides some useful guidance. In the interests of interoperability, however, the following rule is recommended. If an XML entity is in a file, the Byte-Order Mark and encoding declaration are used (if present) to determine the character encoding. IETF RFC 3023 3.6 Summary The following list applies to text/xml, text/xml-external-parsed- entity, and XML-based media types under the top-level type "text" that define the charset parameter according to this specification: o Charset parameter is strongly recommended. o If the charset parameter is not specified, the default is "us- ascii". The default of "iso-8859-1" in HTTP is explicitly overridden. o No error handling provisions. o An encoding declaration, if present, is irrelevant, but when saving a received resource as a file, the correct encoding declaration SHOULD be inserted. The next list applies to application/xml, application/xml-external- parsed-entity, application/xml-dtd, and XML-based media types under top-level types other than "text" that define the charset parameter according to this specification: o Charset parameter is strongly recommended, and if present, it takes precedence. o If the charset parameter is omitted, conforming XML processors MUST follow the requirements in section 4.3.3 of [XML]. Regards Steve Hanson Programming Model Architect, WebSphere Message Brokers, OGF DFDL WG Co-Chair, Hursley, UK, Internet: smh(a)uk.ibm.com, Phone (+44)/(0) 1962-815848 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 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

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Fw: DFDL: Default dfdl:format annotation
by Steve Hanson 11 Nov '09

11 Nov '09

As discussed on the WG call, it is clearer if the use of dfdl:defineXXXX is associated with a named re-usable annotation, and that a 'normal' unnamed DFDL annotation puts properties into use. With that in mind, when dfdl:format is used directly as an annotation on the xs:schema, it is putting properties into use. I therefore withdraw the proposal below. Regards Steve Hanson Programming Model Architect, WebSphere Message Brokers, OGF DFDL WG Co-Chair, Hursley, UK, Internet: smh(a)uk.ibm.com, Phone (+44)/(0) 1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 11/11/2009 17:48 ----- From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org Date: 11/11/2009 11:15 Subject: DFDL: Default dfdl:format annotation Alan and I were discussing this on Friday. We think that the 'default' dfdl:format would be better off contained within a dfdl:defineFormat annotation with no name, zero or one of which may exist in any given xsd. We think it makes things easier to document, specifically that dfdl:format now only appears in one place - as a child of dfdl:defineFormat, and that the term 'unnamed dfdl:defineFormat annotation' may be used to describe this annotation unambiguously. <dfdl:defineFormat> <dfdl:format ........ /> </dfdl:defineFormat> I'd like to add this to the first agenda item for today's call. Regards Steve Hanson Programming Model Architect, WebSphere Message Brokers, OGF DFDL WG Co-Chair, Hursley, UK, Internet: smh(a)uk.ibm.com, Phone (+44)/(0) 1962-815848 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 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

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