- dfdl-wg - lists.ogf.org

Fw: Omitted array occurrences
by Steve Hanson 26 Nov '09

26 Nov '09

As discussed on the call, here is some more in-line below in green and tagged SMH+. A couple of other things when writing this up. 1) I think separatorPolicy="required" is misleading and I'm sure contributed to Tim's questions about behaviour. Here we are using "required" to mean that all delimiters are needed, even when the data itself is not required. I think we should use "always". 2) I'd forgotten that there is also separatorPolicy="suppress". In this case, any missing element does not get a separator. The spec states this " implies the children of the sequence must have dfdl:initiator specified. " but it does not say whether the omission of an initiator is a schema definition error. Should it be? 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 25/11/2009 16:11 ----- From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org Date: 25/11/2009 12:37 Subject: Re: [DFDL-WG] Omitted array occurrences Tim, Alan - my thoughts on this in blue (SMH). 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: Alan Powell/UK/IBM@IBMGB To: Tim Kimber/UK/IBM@IBMGB Cc: dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Date: 19/11/2009 17:30 Subject: Re: [DFDL-WG] Omitted array occurrences Sent by: dfdl-wg-bounces(a)ogf.org Tim Comments below Need more discussion on this 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 From: Tim Kimber/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Date: 19/11/2009 12:07 Subject: [DFDL-WG] Omitted array occurrences What should the DFDL unparser do when some or all of the elements of an array are missing? I have found the following statements in v0.36 which seem relevant: Section 5.2.1 The minOccurs value is used: · to determine if an element declaration or reference is scalar or array · to determine the required minimum number of occurrences of an array both when parsing and unparsing Section 16.13 ( Note : this definition of 'required' is a repeat of the defintion in section 3 ) Definition: 'required' We define the term 'required' as follows: · A scalar element is required. · An element of a fixed-occurrence array is required. · An element of a variable-occurrence array is required if its index is less than or equal to the value of minOccurs. All other elements are not required. ... On unparsing, if an element is required, and is not part of the logical data and the element has a default value specified then it is used, otherwise it is a processing error. Section 17.3.1 : Sequence groups and separators re: the combination of separatorPolicy="suppressAtEnd" and sequenceKind="ordered": 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. Note suppressAtEnd can only be used when there is no clash with delimiters from the containing structure. My interpretation of the specification is: a) if separatorPolicy="require" then the unparser should output a separator for all missing required elements ( whether array members or not ) Is this an additional definition of a 'required' element? In which case the default value should be output. (interestingly because default is a schema property rather than a dfdl property you cannot set a default default.) SMH: The definition of 'required' relates to the data. Here we are talking about whether to output syntax. Strike 'required' from Tim's interpretation and you have the correct interpretation. b) if separatorPolicy="suppressAtEnd" then the unparser should output a separator for all non-trailing missing required elements Should set the default for any required element so it won't be missing. "On unparsing, if an element is required, and is not part of the logical data and the element has a default value specified then it is used, otherwise it is a processing error. " SMH: Tim's interpretation is not complete. The correct interpretation is "...then the unparser should output a separator for all missing elements in the sequence up to and including the last required element.". It is only optional elements beyond the last required element that benefit from this property. c) separators for missing elements must be output regardless of whether the element is required/optional, simple/complex, does/does not have a default value etc. I assume this because the term 'missing' is used rather than the very clearly-defined term 'required'. Missing just means not in the infoset and is orthogonal to optional/required. If you accept this is an additional definition of required then no. But it then forces you to set defaults for minOccurs=0 elements which will only be used in this circumstance. I'm not sure what the default for complex elements would be: all the children must have a default? . SMH: If c) is trying to say that once you have decided, via a) and b), that a separator is needed, then whether it is simple/complex, does/does not have a default, is irrelevant, then I agree. Reading between the lines, I also infer the following rules: d) if an array has maxOccurs="unbounded" and it is missing from the infoset then the unparser will not output any separators for the array e) if an array has maxOccurs!="unbounded" and it is missing from the infoset then the unparser will output a separator for each missing occurrence ( so it will output maxOccurs separators ). If minOccurs > 0 then use default. If minOccurs= 0 then output nothing. I don't think maxOccurs has any effect. SMH+: The behaviour when dealing with a repeating element (minOccurs, maxOccurs) is analogous to dealing with a sequence. You treat up to and including minOccurs as 'required', and anything beyond as 'optional'. Then you apply separatorPolicy property. So "suppressAtEnd" means you only output delimiters up to an including minOccurs, and "required" means you output delimiters up to and including maxOccurs. There's clearly a problem with the combination of maxOccurs="unbounded" and separatorPolicy="required" - this should be a schema definition error. SMH+: It is possible that some models are pretty ambiguous, and that we could be outputting something that is very difficult to parse. If it is possible to use the full DFDL armoury of parsing techniques (speculation, backtracking, data patterns, remodelling as choice and discriminators, etc) then that is a 1.0 limitation. f) if an element contains a child group, and none of the group members are present in the infoset, then the group is 'missing' and the unparser will output a separator for it. Not sure SMH: This is establishing 'missing' for a local group. Sounds right to me. The separator will be output according to a) and b). But because a local group is (1:1) in DFDL, in practice you will always get a separator. SMH+: If a local group needs to be optional it must be wrapped in a complex element. Suggested changes to the specification: - As a minimum, I think it would be useful for the specification to include a definition of 'missing'. 'Not in the infoset' SMH: That's fine for unparsing only. - DFDL does not allow min/maxOccurs on groups, so they implicitly have cardinality 1:1. Specification should specify the behaviour of the unparser when none of a group's members are present in the infoset. Agree. - The wording in 17.3.1 could be more accurate. I don't think the word 'optional' should be there ( if validation is off then the unparser will tolerate missing required elements -No. 'required' is not part of vaildation). I think the words 'trailing' and 'final' are intended to mean the same - we should standardize on 'trailing'. SMH: I agree the words could be improved. See my b) words above for example. 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg 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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OGF document approval process
by Alan Powell 26 Nov '09

26 Nov '09

After failing to get a response from both our area leads I have been in touch with the OGF editor who has pointed me at the OGF process document. http://www.ogf.org/documents/GFD.152.pdf. For recommendations such as DFDL there are two stages. Processing for Proposed Recommendation Documents Processing for Grid Recommendation Documents Note that to become an OGF Recommendation there must be an expert review written summarizing operational experience. "Typically, this will mean that at least two interoperable implementations should be demonstrated" Summary of Document Processing for Proposed Recommendation Documents A document may be returned to an earlier phase of the document process, if deemed necessary. Pre-submission check: Includes consensus within the OGF group, adherence to intellectual property guidelines, assignment of one or more corresponding authors, and group mailing list last call. At this point, OGF group chairs and the appropriate ADs should be informed of the intention to submit Submission: Suitably formatted document, with attention to required elements and intellectual property issues, is submitted to the OGF Editor. Initial Editor review: The OGF Editor reviews the document for completeness, general content, formatting, etc. The OGF Editor will typically confirm the pre-submission check with the AD, who will shepherd the document through the GFSG review. Initial GFSG review: Through the appropriate GFSG council, the GFSG will be given 15 days to read and comment on the document. At the end of that period, the AD will gain consensus from the GFSG as to whether the document is acceptable for advancement to Public Comment. Public Comment: The document enters a 60-day Public Comment, with notification to the OGF community and general public (i.e., through the OGF?s Web site and mailing lists). Review of comments: Authors/editors are asked to respond to Public Comments, and may elect to prepare a new version of the document. If substantial revisions are made, a further Public Comment will be sought. Final GFSG review: The same process as the initial GFSG review, with attention to Public Comments and any further changes to the document. Final Editor review: The OGF Editor will confirm the document is ready for publication. Publication: The OGF Editor will assign a GFD-R-P document number and inform the OGF community of the new document. Summary of Document Processing for Grid Recommendation Documents A document may be returned to an earlier phase of the document process, if deemed necessary. Passage of time: At least 6 months since publication as a GFD-R-P must pass. Process check: When document authors or other interested parties inform the OGF Editor of the desire to move the document to Grid Recommendation status, the Editor will check that requirements are met and seek consensus from the AD that the document is ready for advancement to Grid Recommendation. Document review: A written expert review, summarizing operational experience and documents published that reflect the readiness of the document to become a Grid Recommendation. Other parties may solicit this on behalf of the document authors. It may be submitted to the document authors, the AD, or directly to the OGF Editor. Final document preparation: If small changes are sought to the final document, the submitters must propose them in the form of a replacement document per the Errata process described herein. Public notice: The Editor will inform the OGF community of the intention to move the document to Grid Recommendation, including a summary of or link to the expert review. Final review: The AD will present the result of the review and all other evidence (such as Experimental documents) to the appropriate Council, with a recommendation for whether to change the status to a Grid Recommendation. The Council will be given 15 days to read and comment on the document. At the end of that period, the AD will gain consensus as to whether the document is acceptable for advancement. Republication: The OGF Editor will replace GFD-R-P with GFD-R in the document, and apply any other needed changes. The Editor will inform the OGF community of the new document. 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 25 Nov '09

25 Nov '09

I'd like to record what was discussed and raise another point which Alan pointed out after meeting, Discussions in the meeting - dfdl:lengthKind applies only to the element on which it is specified. It has no effect whatever on the parsing of child elements/groups. - there may be some value in tolerating simple elements of type xs:string with dfdl:representation="binary". Might be useful for schemas where dfdl:representation="binary" throughout. - Currently, the position of the WG is that parsers should *always* scan to extract the text representation if there is any terminating markup in scope. Even if lengthKind='explicit'. - TK proposed the scheme outlined in his previous email, in which dfdl:lengthKind alone specifies how the parser should extract the text representation. If lengthKind="explicit", scanning is switched off and dfdl:length is used. If lengthKind="delimited" the text rep is extracted by scanning and length is ignored. - A refinement was discussed whereby dfdl:length would be checked after a scan has been performed if dfdl:lengthKind="delimited". This would make the modeling of some common formats simpler, and avoid the need for a dfdl:assert to enforce the length constraint. - MB raised the possibility that we could actually disallow dfdl:length if lengthKind='delimited'. This is the most conservative position, but general opinion was that it would be too restrictive. There still might be some value in disallowing dfdl:length for other lengthKinds. Discussions after the meeting - Alan pointed out that lengthKind="explicit" does not necessarily mean that the length of the field is fixed. dfdl:length might be specified as a DFDL expression. A common reason for doing that would be to obtain the element's length from an earlier integer field. As currently specified, if there was any markup in scope, the text rep would be extracted by scanning. Restatement of my position after today's meeting: I'm now even more convinced that dfdl:lengthKind="explicit" should switch off scanning. Here's why: a) The enumerations of lengthKind are explicit, implicit, prefixed, delimited, pattern, endOfParent. The presence of 'delimited' in that list means that in some users' minds, the other enumerations are going to be interpreted as *alternatives* to 'delimited'. b) If there's markup in scope, scanning cannot be switched off by any means. Not even by setting lengthKind='explicit' AND obtaining dfdl:length from a previous integer field. I think that's very counter-intuitive. 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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Omitted array occurrences
by Tim Kimber 25 Nov '09

25 Nov '09

What should the DFDL unparser do when some or all of the elements of an array are missing? I have found the following statements in v0.36 which seem relevant: Section 5.2.1 The minOccurs value is used: · to determine if an element declaration or reference is scalar or array · to determine the required minimum number of occurrences of an array both when parsing and unparsing Section 16.13 ( Note : this definition of 'required' is a repeat of the defintion in section 3 ) Definition: 'required' We define the term 'required' as follows: · A scalar element is required. · An element of a fixed-occurrence array is required. · An element of a variable-occurrence array is required if its index is less than or equal to the value of minOccurs. All other elements are not required. ... On unparsing, if an element is required, and is not part of the logical data and the element has a default value specified then it is used, otherwise it is a processing error. Section 17.3.1 : Sequence groups and separators re: the combination of separatorPolicy="suppressAtEnd" and sequenceKind="ordered": 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. Note suppressAtEnd can only be used when there is no clash with delimiters from the containing structure. My interpretation of the specification is: a) if separatorPolicy="require" then the unparser should output a separator for all missing required elements ( whether array members or not ) b) if separatorPolicy="suppressAtEnd" then the unparser should output a separator for all non-trailing missing required elements c) separators for missing elements must be output regardless of whether the element is required/optional, simple/complex, does/does not have a default value etc. I assume this because the term 'missing' is used rather than the very clearly-defined term 'required'. Reading between the lines, I also infer the following rules: d) if an array has maxOccurs="unbounded" and it is missing from the infoset then the unparser will not output any separators for the array e) if an array has maxOccurs!="unbounded" and it is missing from the infoset then the unparser will output a separator for each missing occurrence ( so it will output maxOccurs separators ). f) if an element contains a child group, and none of the group members are present in the infoset, then the group is 'missing' and the unparser will output a separator for it. Suggested changes to the specification: - As a minimum, I think it would be useful for the specification to include a definition of 'missing'. - DFDL does not allow min/maxOccurs on groups, so they implicitly have cardinality 1:1. Specification should specify the behaviour of the unparser when none of a group's members are present in the infoset. - The wording in 17.3.1 could be more accurate. I don't think the word 'optional' should be there ( if validation is off then the unparser will tolerate missing required elements ). I think the words 'trailing' and 'final' are intended to mean the same - we should standardize on 'trailing'. 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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Fw: Agenda for OGF DFDL WG call 25 November 2009 - 13:00UK (8:00 ET)
by Alan Powell 24 Nov '09

24 Nov '09

With current actions attached 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 ----- Forwarded by Alan Powell/UK/IBM on 24/11/2009 17:18 ----- From: Alan Powell/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Date: 24/11/2009 17:05 Subject: [DFDL-WG] Agenda for OGF DFDL WG call 25 November 2009 - 13:00UK (8:00 ET) 1. 045 Resolving points of uncertainty - Disciminators Continue discussion of semantics of discriminators and arrays. See email from Alan 2. 045 - parsing rules for determining length Continue discussion on how to 'turn off scanning' for text elements. 3. SeparatorPolicy=require and defaulting arrays and sequences Tim has asked for clarification of the rules for when elements are missing and separator policy is required. See email 4. Clarification of postfix separators, terminators,finalTerminatorCanBeMissing see email from Tim 5. Go through remaining actions 6. Test suite for DFDL Discuss Mike's e-mail and what IBM is doing as part of its implementation work 7. OGF28 Call for papers 8. 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 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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg 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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Agenda for OGF DFDL WG call 25 November 2009 - 13:00UK (8:00 ET)
by Alan Powell 24 Nov '09

24 Nov '09

045 Resolving points of uncertainty - Disciminators Continue discussion of semantics of discriminators and arrays. See email from Alan 045 - parsing rules for determining length Continue discussion on how to 'turn off scanning' for text elements. SeparatorPolicy=require and defaulting arrays and sequences Tim has asked for clarification of the rules for when elements are missing and separator policy is required. See email Clarification of postfix separators, terminators,finalTerminatorCanBeMissing see email from Tim 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 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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DFDL Discriminators discussion
by Alan Powell 24 Nov '09

24 Nov '09

Following on from Stephanie's WTX example on last weeks call I think that restricting discriminator to resolving their parents provides the level of control that we need. I have updated Mike's example with this syntax Note I have flattened the schema as I find that easier to read and 'enhanced' some the the dfdl properties. To illustrate the flexibility if 'L' had a test="{ fn:exists( . ) }" discriminator then if an L record had been found then the parse would fail rather than backtracking to Blob. 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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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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