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Minutes for OGF DFDL Working Group Call, May-20-2009
by Alan Powell 21 May '09

21 May '09

Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, May-20-2009 Meeting opened, 14:00 UK Attendees Steve Hanson (IBM) Mike Beckerle (Oco) Suman Kalia (IBM) Alan Powell (IBM) Apologies Dave Glick (drac) Agenda: 1. Go through actions. Updated below: 2. Codepage for text items in infoset. It is proposed that text values in the infoset should be ISO10646. Agreed 3. Annotations on Top Level element Highlighted usability problem that the top level element cannot inherit dfdl properties from scope as no complex type has be used yet. A reference to a defineFormat needs to on both the top element and its complex type. Suggested that could add a defineFormat property that used that defineFormat to set defaults for the schema but that would cause problems with include/import. Solutions seemed worse than the problem so will leave it as it is. 4 .Scoping of elements and Types MB has pointed out a problem with the current scoping rules and proposed that propoeties on an element should override those on its type. Discussion on whether an element was an instance of a simpleType or enclosed a simple type. For example if dfd:initiator on both element and simple type do you get one or two initiators.. Also discussed separating dfdl properties between element and type so that none were common. The need to be able to use XSD simple types directly made this impossible. Decided that an element is an instance of a simple type and that properties on the element override those on the simple type. Noted that this is different from complex type. Action: AP to document change to simple type scoping rules. 5. Scoping rules for assert/discriminator and other annotations The scoping rules for non-format annoations are not defined. AP to make a proposal 6. Need for the equivalent of WTX Restart Restart indicates where in the schema to restart parsing when unable to correctly parse content Could be viewed as an implementation decision. More investigation needed 7. Built-in Specifications Spec Section 23 Built-in Specifications TBD: this section gives the names, import URLs for, rep-property definition sets, property definitions, etc. for the built-in named format definitions The intention is that a small number of built-in specifications are provided for common format styles. 8. AOB Next call 27 May 14:00 UK Scheduled for 1 hour Meeting closed, 16:10 UK Actions raised at this meeting No Action 045 20/05 AP: Speculative Parsing 046 20/05 AP: Document changes to simple type scoping 047 20/05 AP: Scoping for non-format annotations 048 20/05: AP investigate Restart 049 20/05 AP Built-in specification description and schemas 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 026 SH: Envelopes and Payloads 08/04: Not discussed explicity, but recursive use of DFDL is tied up with this 22/04: Two aspects. Firstly compositional - do sufficient mechanisms exist to model an envelope with a payload that varies. Secondly markup syntax - this might be defined in the envelope. The second of these is very much tied up with the variable markup action 028, so will be considered there. SH to verify the composition aspect. 29/04: SH and AP working on proposal. related to Action 028 06/05: No progress 06/05: No progress 20/05: No Progress 027 SH: Property precedence tables 08/04: Not discussed 22/04: Two things missing from the existing precedence trees. Firstly, does not show alternates (eg, initiator v initiatorkind). Secondly, need a tree per concrete DFDL object (eg, element). SH to update. 29/04: No progress 06/05: SH is updating tables which will be ready for next call 13/05: SH emailed updated version. AP commented.. See minutes for issues and property changes. 20/05: Updated version circulated. Review before next call and be ready for vote. 028 SH: Variable markup 08/04: Discussed briefly at end of call, IBM to see whether there any use cases that require recursive use of DFDL. 15/04: Use case was distributed and will be discussed on next call. 22/04: The use case in question is EDI where the terminating markup for the payload segments is defined in the ISA envelope segment. The markup is modelled as an element of simple type where the allowable markup values are defined as enums on the type. But we need to handle two cases - firstly where the envelope is present, so the value used by the payload is taken from the envelope. Secondly where only the payload is present. Here we need a way of scanning for all the enum values, and adopting the one we actually find, when parsing. And using a default when unparsing. SH to explore use of a DFDL variable, where the variable has a default, but also has a type that is the same as the markup element - that way we get to use the enums without defining everything twice. 29/04: SH and AP working on proposal. 06/05: No progress 13/05: No progress 20/05: No Progress 029 MB: valueCalc (output length calculation) 08/04: Not discussed 22/04: Action allocated to MB, this is to complete the work started at the Hursley WG F2F meeting. 29/04: No progress 06/05: MB will have update for next call 13/05: MB will have update for next call 20/05: Some progress. will be circulated this week 032 DG: Investigate compatibility between DFDL infoset and XDM 08/04: No update 22/04: No update 29/04: No update 06/05: DG indicates will have update next week 13/05: see minutes 20/05: No Progress 033 AP/TK: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice. 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) 036 SH: Provide use case for floating component in a sequence 08/04: Raised 15/04: Use case sent and discussed. SH to do further investigation 22/04: IBM feedback from WTX team is that alternate suggested ways of modelling the EDI floating NTE segment have significant usability issues. The DFDL principle is that for a problem that can be expressed as two-layered, then two DFDL models are needed. The EDI NTE segment does not fall into this though, as its use is on a per sequence basis. Ongoing. 29/04: Agreed that need to be in V1. SH to make a proposal 06/05: No progress 20/05: SH has almost completed the proposal 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 038 MB: Submit response to OMG RFI for non-XML standardization 22/04: First step is for MB to mail the OGF Data Area chair to say that we want to submit 29/04: MB has been in contact with OMG and will sunbit dfdl. 06/05: MB has prepared response to OMG. Will send DFDL sepc v033 20/05: Response has been sent to OMG based on v034 039 SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. Close 042 MB: Complete variable specification. To include how properties such as encoding can be set externally. Must be a known variable name. 06/05: No progress 20/05: AP to make proposal 043 13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct? 20/05: SH No progress 044 13/05: Bidi 20/05: AP: will check what IBM products support. 045 20/05: AP: Speculative parsing Closed actions: 039 SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. SKK owner of dfdl schema and will update as properties change Closed 040 SH: LengthKind on complex objects. 29/04: All send comment before next call 06/05: See minutes. Agreed to remove lengthKind from sequence and choice. 20/05: Closed moved to workitem 041 AP: UnorderedInitiated 29/04: All: Review for next call 06/05: See minutes: Agreed to generalize to all sequences 20/05: Closed. Move to work item Work items: No Item target version status 003 Variables - ??, 2008 (Mike) 005 Improvements on property descriptions - ??, 2008 (All - split TBD) 006 Envelopes and Payloads (Steve) - Apr 30, 2008 007 (from draft 32) valueCalc (Mike) - ??, 2008 mostly complete 008 (from draft 32) Property precedence for writing (Steve) - under review 009 (from draft 32) Variable markup (Steve) - Mar 31, 2008 proposal needs writing up 011 (from draft 32) How speculative parsing works (combining choice and variable-occurence - currently these are separate) ??, 2008 (IBM) in progress 012 (from draft 32) Reordering the properties discussion: move representation earlier, improve flow of topics ??, 2008 (Alan) not started 027 Calendar schemes 034 032 Floating components 033 Changes from action 020 and 027 - renaming properties etc 035 Remove unorderedInitiated, add initiated content (a041) 036 Update dfdl schema with change properties (Suman) 037 Infoset text codepage 038 Improve length section 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: Applying DFDL annotations to elements
by Steve Hanson 20 May '09

20 May '09

To apply DFDL annotations to a top-level element in a DFDL xsd, most modellers would use the dfdl:element dfdl:ref property to refer to a named dfdl:defineFormat block that set up the necessary defaults for all the DFDL properties. To avoid having to re-state the dfdl:ref property on every object that comprises the format, most modellers would also use the dfdl:complexType dfdl:ref property to scope the same dfdl:defineFormat block. The xsd would look like below. <xs:schema ...> <xs:annotation><xs:appinfo source=?http://www.ogf.org/dfdl/?> <dfdl:defineFormat name=?textFormat1"> <dfdl:format encoding="utf-8" separator="\n" representation=?text? lengthKind="delimited" /> </dfdl:defineFormat> </xs:appinfo></xs:annotation> ... <xs:element name="textDoc" dfdl:ref="textFormat1" dfdl:lengthKind="implicit"> <xs:complexType dfdl:ref="textFormat1"> <xs:sequence> ... </xs:sequence> </xs:complexType> </xs:element> ... </xs:schema> It's not possible to put DFDL defaults in scope for the whole format with a single dfdl:ref property. I think this is a side-effect of removing the dfdl:appliesTo property. If this is thought to be an issue, there are a couple of options: One is to say that a complex type can be the top-level object. This is the case with several XML based systems. It works with XML because the XML instance document provides the name of top level element in the infoset via its tag. This is not the case with DFDL where the name is commonly not carried with the format. So we'd have no name for the infoset. Another is to provide a new property on dfdl:defineFormat, which says this dfdl:defineFormat is the default for all top-level objects in the xsd. Any top-level object that remained silent as to its dfdl:ref would get the default applied. I'm not sure whether this makes the model too opaque though. No more so than the existing scoping rules, I suspect. Any other opinions or suggestions welcome. Regards Steve Hanson Programming Model Architect WebSphere Message Brokers 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

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Fw: DFDL: Action 027 - second rework of property precedence
by Steve Hanson 20 May '09

20 May '09

Alan, Mike Thanks for the feedback. Here is latest version that addresses all comments except where noted below. The biggest changes are: - Trimming & padding are now part of the 'extraction' & 'insertion' phases, and not conversion. - Complex element separated from simple element - Simple type / local element / global element distinctions called out - Repeat properties pulled forward into own phase Notes: 1) Mike - I agree that dfdl:inputValueCalc and dfdl:outputValueCalc should not be allowed in dfdl:format annotation (ie, scoping). Spec & xsds should be updated. 2) Mike - you say that escape schemes are needed when looking for initiators - we should discuss - I'm not sure this is a real requirement in practice - I've never come across this. 3) Mike - the DFDL parser/unparser is driven by model position - not by infoset position - you only get elements in the infoset. 4) Mike - I don't think that dfdl:initiatedContent is needed when unparsing. 5) Alan - encoding and byteOrder do apply for sequence, choice and any, because there could be markup involved. 6) Alan - lengthKind = 'pattern' - is this something that we should support on complex elements - assumed so for now. Regards Steve Hanson Programming Model Architect WebSphere Message Brokers Hursley, UK Internet: smh(a)uk.ibm.com Phone (+44)/(0) 1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 13/05/2009 10:25 ----- My markup on this attached - mostly using comment balloons on the side. Mike Beckerle | OGF DFDL WG Co-Chair | CTO | Oco, Inc. Tel: 781-810-2125 | 100 Fifth Ave., 4th Floor, Waltham MA 02451 | mbeckerle.dfdl(a)gmail.com Alan Powell/UK/IBM 11/05/2009 16:57 To Steve Hanson/UK/IBM@IBMGB cc dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Subject Re: [DFDL-WG] DFDL: Action 027 - rework of property precedence - plus issues arising Steve Comments I don't think the tables answer the precedence of padding, escaping and encoding that we had when discussing escape schemes. On parsing it should be remove padding, remove escape characters, apply encoding. On unparsing it is the reverse but the tables look the same. I think the difficulty is that escape scheme is used for identification and extraction but also during conversion. I don't think the core properties (inputvaluecalc, etc) apply to sequence, choice or any. xxxPadKind is checked before xxxPadCharacter, xxpadxxx Calendar-binary. binaryCalendarFormatRef is only used when binCalRep = packed or bcd 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: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Date: 08/05/2009 17:24 Subject: [DFDL-WG] DFDL: Action 027 - rework of property precedence - plus issues arising I've created a separate property precedence for each schema object that can carry non-scoping DFDL properties (attached for review). The following issues were noted: 1) Missing property dfdl:textBooleanJustification - similar properties exist for string, number and calendar types. 2) What is the rule when the same DFDL properties occur on a xs:simpleType and a xs:element that uses that type? Does this work a) like element/group references (ie, properties combined with element winning) or b) like complex element and its sequence (ie, element and simpleType are considered separate objects)? I don't think section 10 covers this case. 3) Should we allow the DFDL nil & default control properties on a simple type? xs:nillable and xs:default are element only attributes in xsd. Spec currently allows this. 4) Should we allow DFDL occurs properties on global elements? Whether something repeats is a particle thing. Spec currently allows this. (IBM's WTX and MRM don't allow this). 5) Missing work item to get BiDi properties into shape and incorporated into spec. Should these be grouped, like escape scheme, calendar scheme, etc? Do they apply to calendar and number types? 6) Should dfdl:integerBooleanXXXRep be renamed dfdl:binaryBooleanXXXRep ? 7) We might want to reconsider the name of the new flag dfdl:initiated - it could be read that the xs:sequence itself is initiated rather than its children. 8) Should dfdl:initiated also apply to xs:choice? 9) Draft 33 property precedence had dfdl:outputLengthCalc - but that is not in the spec anywhere else? Regards Steve Hanson Programming Model Architect WebSphere Message Brokers 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 [attachment "Property Precedence 034.doc" deleted by Alan Powell/UK/IBM] -- 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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Agenda for OGF WG call 20 May 2009
by Alan Powell 20 May '09

20 May '09

Note: the call is scheduled for 2 hours Agenda: 1. Go through actions. 2. Codepage for text items in infoset. It is proposed that text values in the infoset should be ISO10646. 3. Annotations on Top Level element 4 .Scoping of elements and Types MB has pointed out a problem with the current scoping rules and proposed that propoeties on an element should override those on its type. 5. Scoping rules for assert/discriminator and other annotations 6. Need for the equivalent of WTX Restart Restart indicates where in the schema to restart parsing when unable to correctly parse content 7. Built-in Specifications Spec Section 23 Built-in Specifications TBD: this section gives the names, import URLs for, rep-property definition sets, property definitions, etc. for the built-in named format definitions 8. AOB 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. 026 SH: Envelopes and Payloads 08/04: Not discussed explicity, but recursive use of DFDL is tied up with this 22/04: Two aspects. Firstly compositional - do sufficient mechanisms exist to model an envelope with a payload that varies. Secondly markup syntax - this might be defined in the envelope. The second of these is very much tied up with the variable markup action 028, so will be considered there. SH to verify the composition aspect. 29/04: SH and AP working on proposal. related to Action 028 06/05: No progress 06/05: No progress 027 SH: Property precedence tables 08/04: Not discussed 22/04: Two things missing from the existing precedence trees. Firstly, does not show alternates (eg, initiator v initiatorkind). Secondly, need a tree per concrete DFDL object (eg, element). SH to update. 29/04: No progress 06/05: SH is updating tables which will be ready for next call 13/05: SH emailed updated version. AP commented.. See minutes to issues. 028 SH: Variable markup 08/04: Discussed briefly at end of call, IBM to see whether there any use cases that require recursive use of DFDL. 15/04: Use case was distributed and will be discussed on next call. 22/04: The use case in question is EDI where the terminating markup for the payload segments is defined in the ISA envelope segment. The markup is modelled as an element of simple type where the allowable markup values are defined as enums on the type. But we need to handle two cases - firstly where the envelope is present, so the value used by the payload is taken from the envelope. Secondly where only the payload is present. Here we need a way of scanning for all the enum values, and adopting the one we actually find, when parsing. And using a default when unparsing. SH to explore use of a DFDL variable, where the variable has a default, but also has a type that is the same as the markup element - that way we get to use the enums without defining everything twice. 29/04: SH and AP working on proposal. 06/05: No progress 13/05: No progress 029 MB: valueCalc (output length calculation) 08/04: Not discussed 22/04: Action allocated to MB, this is to complete the work started at the Hursley WG F2F meeting. 29/04: No progress 06/05: MB will have update for next call 13/05: MB will have update for next call 032 DG: Investigate compatibility between DFDL infoset and XDM 08/04: No update 22/04: No update 29/04: No update 06/05: DG indicates will have update next week 13/05: see minutes 033 AP/TK: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice. 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 036 SH: Provide use case for floating component in a sequence 08/04: Raised 15/04: Use case sent and discussed. SH to do further investigation 22/04: IBM feedback from WTX team is that alternate suggested ways of modelling the EDI floating NTE segment have significant usability issues. The DFDL principle is that for a problem that can be expressed as two-layered, then two DFDL models are needed. The EDI NTE segment does not fall into this though, as its use is on a per sequence basis. Ongoing. 29/04: Agreed that need to be in V1. SH to make a proposal 06/05: No progress 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. 038 MB: Submit response to OMG RFI for non-XML standardization 22/04: First step is for MB to mail the OGF Data Area chair to say that we want to submit 29/04: MB has been in contact with OMG and will sunbit dfdl. 06/05: MB has prepared response to OMG. Will send DFDL sepc v033 039 SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 040 SH: LengthKind on complex objects. 29/04: All send comment before next call 06/05: See minutes. Agreed to remove lengthKind from sequence and choice. 041 AP: UnorderedInitiated 29/04: All: Review for next call 06/05: See minutes: Agreed to generalize to all sequences 042 MB: Complete variable specification. To include how properties such as encoding can be set externally. Must be a known variable name. 06/05: No progress 043 13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct? 044 13/05: Bidi 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: Action 027 - rework of property precedence - plus issues arising
by Steve Hanson 19 May '09

19 May '09

I've created a separate property precedence for each schema object that can carry non-scoping DFDL properties (attached for review). The following issues were noted: 1) Missing property dfdl:textBooleanJustification - similar properties exist for string, number and calendar types. 2) What is the rule when the same DFDL properties occur on a xs:simpleType and a xs:element that uses that type? Does this work a) like element/group references (ie, properties combined with element winning) or b) like complex element and its sequence (ie, element and simpleType are considered separate objects)? I don't think section 10 covers this case. 3) Should we allow the DFDL nil & default control properties on a simple type? xs:nillable and xs:default are element only attributes in xsd. Spec currently allows this. 4) Should we allow DFDL occurs properties on global elements? Whether something repeats is a particle thing. Spec currently allows this. (IBM's WTX and MRM don't allow this). 5) Missing work item to get BiDi properties into shape and incorporated into spec. Should these be grouped, like escape scheme, calendar scheme, etc? Do they apply to calendar and number types? 6) Should dfdl:integerBooleanXXXRep be renamed dfdl:binaryBooleanXXXRep ? 7) We might want to reconsider the name of the new flag dfdl:initiated - it could be read that the xs:sequence itself is initiated rather than its children. 8) Should dfdl:initiated also apply to xs:choice? 9) Draft 33 property precedence had dfdl:outputLengthCalc - but that is not in the spec anywhere else? Regards Steve Hanson Programming Model Architect WebSphere Message Brokers 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

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Grammar issue - simple and complex asymetry
by Mike Beckerle 19 May '09

19 May '09

The draft 034 grammar productions do not allow for a separate prefix/suffix for a simple type as distinguished from the element having that type. Draft 034 does allow for an element of complex type to have a separate prefix and suffix for the element itself and another one for the sequence or choice inside it. I've come to believe this is a mistake and I suggest a fix below. Right now the grammar is: Element = SimpleElement | ComplexElement SimpleElement = Prefix SimpleContent Suffix SimpleContent = StringText // terminal. No more prefixes/suffixes ComplexElement = Prefix ComplexContent Suffix ComplexContent = Sequence | Choice Sequence = Prefix SequenceContent Suffix Choice = Prefix ChoiceContent Suffix So, if I do: <complexType dfdl:initiator="[" dfdl:terminator="]"> ... <element name="y"> <complexType> <sequence dfdl:separator="," > <element name="x" type="int"/> <element name="z" type="int"/> </sequence> </complexType> </element> ... </complexType> I have two prefix opportunities. I can flatten the productions above to: ComplexElement = Prefix Prefix SequenceContent Suffix Suffix An instance of this type would look like [[[5],[6]]]. That is, for complex types, there are separate prefix and suffix regions for the element, and for the model-group which makes up its content. The first [ initiates element y. The second [ initiates the sequence The third [ initiates element x. This same behavior is not true for simple types: <complexType dfdl:initiator="[" dfdl:terminator="]"> ... <element name="y" > <simpleType> <restriction base="int"/> </simpleType> </element> ... </complexType> This can only mean [5]. The grammar, as formulated in draft 034, does not allow for more than one prefix or suffix. The [ is the initiator of element y. I believe we should fix this as follows. New grammar: Element = SimpleElement | ComplexElement SimpleElement = Prefix SimpleContent Suffix SimpleContent = StringText ComplexElement = ComplexContent // Note: no more surrounding prefix suffix. ComplexContent = Sequence | Choice Sequence = Prefix SequenceContent Suffix Choice = Prefix ChoiceContent Suffix The above grammar arranges for an element of complex type and its model group to both taken together specify a single prefix and suffix. Revisiting our example (just repeating it here): <complexType dfdl:initiator="[" dfdl:terminator="]"> ... <element name="y"> <complexType> <sequence dfdl:separator="," > <element name="x" type="int"/> <element name="z" type="int"/> </sequence> </complexType> </element> ... </complexType> An instance now would look like [[5],[6]] The first [ is the initiator of element y, which is the same as the initiator of the sequence that is its type. The second [ is the initiator of element x. (which is the same as the initiator of the int that is its type) I believe this is more sensible, as it makes the behavior of simple and complex types more similar. It begs the question of how one combines conflicting properties on an element with the properties on the type, and even the model group inside the type in the complex case. Because all these properties are describing the same syntax fields in the grammar. That's a separate topic in a subsequent email.

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elements and combining properties with their types
by Mike Beckerle 19 May '09

19 May '09

I spent some real time thinking about this issue today. Attached is a memo on the subject which is big enough that I didn't want to just make it an email body. Summary: I think current 034 semantics are broken and should be fixed along the lines of the element - overrides - type principle. The example in the scoping section is not right. But the issue has some depth to it. E.g., I think the grammar productions are broken currently and we need to fix those also. See attached. ...mike Mike Beckerle | OGF DFDL WG Co-Chair | CTO | Oco, Inc. Tel: 781-810-2125 | 100 Fifth Ave., 4th Floor, Waltham MA 02451 | <mailto:mbeckerle.dfdl@gmail.com> mbeckerle.dfdl(a)gmail.com

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More schema work - I got inspired!
by Mike Beckerle 16 May '09

16 May '09

Suman et al, I got inspired by your XML Schema for DFDL annotations. 1) I fixed a few things in it. It is attached. I renamed it with suffix to make it "...033-1.xsd" You can diff it against yours to find the changes. Some are: no 'all' groups. Added dfdl:simpleType (which I think we forgot, but we need.) took separator props off element and simple type, a few other cleanups. These are a start on the version 034 changes. Then I really got going.... 2) I created an XML Schema for the DFDL subset of XML Schema There is this XML Schema for XML Schema around. I subsetted it to match the DFDL spec. If you use this and your DFDL annotation schema together, under Eclipse, it's really quite a reasonably electric DFDL environment. I have a test file that uses all the annotations I could think of. So I've attached 3 files: DFDL_v1_033-1.xsd - updated DFDL annotations schema DFDLSubsetOfXMLSchema_v1_034.xsd - schema for DFDL subset of XSD strictDFDLChecking.xml - example The example is a bit tricky with the namespace prefixes - it defines the "xsd" prefix to be the DFDLSubset schema, not the ordinary XSD schema. Anyway, I hope this contribution is helpful. It was kind of fun to do. ...mike P.S., somewhere in the various archive files is a stylesheet that turns short-form annotations on DFDL schemas into the longer form annotations. I can dig this out if it is of interest. Mike Beckerle | OGF DFDL WG Co-Chair | CTO | Oco, Inc. Tel: 781-810-2125 | 100 Fifth Ave., 4th Floor, Waltham MA 02451 | <mailto:mbeckerle.dfdl@gmail.com> mbeckerle.dfdl(a)gmail.com

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Minutes from OGF DFDL Working Group Call, May-14-2009
by Alan Powell 14 May '09

14 May '09

Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, May-14-2009 Meeting opened, 14:00 UK Attendees Steve Hanson (IBM) Mike Beckerle (Oco) Suman Kalia (IBM) Alan Powell (IBM) Dave Glick (drac) Apologies Agenda: 1. Go through actions. Action 027 Property precedence tables 1) Missing property dfdl:textBooleanJustification --added 2) What is the rule when the same DFDL properties occur on a xs:simpleType and a xs:element that uses that type? Does this work a) like element/group references (ie, properties combined with element winning) or b) like complex element and its sequence (ie, element and simpleType are considered separate objects)? I don't think section 10 covers this case. 3) Should we allow the DFDL nil & default control properties on a simple type? Only on element 4) Should we allow DFDL occurs properties on global elements? - No. 5) Missing work item to get BiDi properties into shape and incorporated into spec. Should these be grouped, like escape scheme, calendar scheme, etc? Do they apply to calendar and number types? - Action created 6) Should dfdl:integerBooleanXXXRep be renamed dfdl:binaryBooleanXXXRep ? - agreed 7) We might want to reconsider the name of the new flag dfdl:initiated - it could be read that the xs:sequence itself is initiated rather than its children. - renamed initiatedContent 8) Should dfdl:initiated also apply to xs:choice? - yes 9) Draft 33 property precedence had dfdl:outputLengthCalc - was removed. Action 028 Dfdl infoset and XDM Discussed DG document. SH commented that document tried to make the dfdl infoset be XDM rather than be compatible with XDM. DFDL does not need all the complexity in XDM. Need a mapping between dfdl infoset and XDM to make sure there are no uneccessary differences. This needs to consider character sets, validation (types for unvalidated data) and arrays 2. Check Work items - add incorporate DG comments on 033 3. Annotations on Top Level element Not discussed: Please review before next call 4. Scoping rules for assert/discriminator and other annotations Not discussed: Please review before next call 5. Comments latest version (034) Not discussed: Please review before next call 6. AOB Next call 13 May 14:00 UK Note: Scheduled for 2 hours Meeting closed, 15:10 UK Actions raised at this meeting No Action 043 13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct? 044 13/05: Bidi 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. 026 SH: Envelopes and Payloads 08/04: Not discussed explicity, but recursive use of DFDL is tied up with this 22/04: Two aspects. Firstly compositional - do sufficient mechanisms exist to model an envelope with a payload that varies. Secondly markup syntax - this might be defined in the envelope. The second of these is very much tied up with the variable markup action 028, so will be considered there. SH to verify the composition aspect. 29/04: SH and AP working on proposal. related to Action 028 06/05: No progress 06/05: No progress 027 SH: Property precedence tables 08/04: Not discussed 22/04: Two things missing from the existing precedence trees. Firstly, does not show alternates (eg, initiator v initiatorkind). Secondly, need a tree per concrete DFDL object (eg, element). SH to update. 29/04: No progress 06/05: SH is updating tables which will be ready for next call 13/05: SH emailed updated version. AP commented.. See minutes to issues. 028 SH: Variable markup 08/04: Discussed briefly at end of call, IBM to see whether there any use cases that require recursive use of DFDL. 15/04: Use case was distributed and will be discussed on next call. 22/04: The use case in question is EDI where the terminating markup for the payload segments is defined in the ISA envelope segment. The markup is modelled as an element of simple type where the allowable markup values are defined as enums on the type. But we need to handle two cases - firstly where the envelope is present, so the value used by the payload is taken from the envelope. Secondly where only the payload is present. Here we need a way of scanning for all the enum values, and adopting the one we actually find, when parsing. And using a default when unparsing. SH to explore use of a DFDL variable, where the variable has a default, but also has a type that is the same as the markup element - that way we get to use the enums without defining everything twice. 29/04: SH and AP working on proposal. 06/05: No progress 13/05: No progress 029 MB: valueCalc (output length calculation) 08/04: Not discussed 22/04: Action allocated to MB, this is to complete the work started at the Hursley WG F2F meeting. 29/04: No progress 06/05: MB will have update for next call 13/05: MB will have update for next call 032 DG: Investigate compatibility between DFDL infoset and XDM 08/04: No update 22/04: No update 29/04: No update 06/05: DG indicates will have update next week 13/05: see minutes 033 AP/TK: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice. 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 036 SH: Provide use case for floating component in a sequence 08/04: Raised 15/04: Use case sent and discussed. SH to do further investigation 22/04: IBM feedback from WTX team is that alternate suggested ways of modelling the EDI floating NTE segment have significant usability issues. The DFDL principle is that for a problem that can be expressed as two-layered, then two DFDL models are needed. The EDI NTE segment does not fall into this though, as its use is on a per sequence basis. Ongoing. 29/04: Agreed that need to be in V1. SH to make a proposal 06/05: No progress 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. 038 MB: Submit response to OMG RFI for non-XML standardization 22/04: First step is for MB to mail the OGF Data Area chair to say that we want to submit 29/04: MB has been in contact with OMG and will sunbit dfdl. 06/05: MB has prepared response to OMG. Will send DFDL sepc v033 039 SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 040 SH: LengthKind on complex objects. 29/04: All send comment before next call 06/05: See minutes. Agreed to remove lengthKind from sequence and choice. 041 AP: UnorderedInitiated 29/04: All: Review for next call 06/05: See minutes: Agreed to generalize to all sequences 042 MB: Complete variable specification. To include how properties such as encoding can be set externally. Must be a known variable name. 06/05: No progress 043 13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct? 044 13/05: Bidi Closed actions: 020 SH: Resolve packedDecimalSignCodes behaviour depends on NumberCheckPolicy 22/10: No progress 10/12: added how to decide to overpunch and sign position 11/02: proposal largely agreed. SH to make minor changes 18/02: AP to document unsigned type behaviour 25/02: no progress 08/04: Not discussed 22/04: SH to complete last remaining issue, which is the behaviour when logical type is signed/unsigned and the physical type is unsigned/signed. 29/04: SH had identified a problem with definition values and types in the infoset and will email proposal. DG to be asked to accelerate action 032 to see if helps 06/05: No progress 13/05: Original problem has been resolved and added to v034. CLOSED Will open new action for signed/unsigned types in the infoset. Work items: No Item target version status 001 String XML type (Ian P) - Apr 30, 2008 deferred 002 Escape schemes (Ian P) - Apr 30, 2008 034 003 Variables - ??, 2008 (Mike) 005 Improvements on property descriptions - ??, 2008 (All - split TBD) 006 Envelopes and Payloads (Steve) - Apr 30, 2008 007 (from draft 32) valueCalc (Mike) - ??, 2008 mostly complete 008 (from draft 32) Property precedence for writing (Steve) - under review 009 (from draft 32) Variable markup (Steve) - Mar 31, 2008 proposal needs writing up 010 (from draft 32) Assertions, discriminators and choice, including discussion of timing option (Suman) - Mar 31, 2008 (A033) 034 in progress 011 (from draft 32) How speculative parsing works (combining choice and variable-occurence - currently these are separate) ??, 2008 (IBM) in progress 012 (from draft 32) Reordering the properties discussion: move representation earlier, improve flow of topics ??, 2008 (Alan) not started 025 Augmented infoset and unparsing (Alan) 034 added but needs work 026 Remove duration 034 027 Calendar schemes 034 028 Validation ranges (A035) 034 029 Decimals (A020) - document unsigned type behaviour - packedDecimalSignCodes behaviour depends on NumberCheckPolicy 034 030 Remove redundant properties, fix examples. (A036) 034 031 Specialized annotations 034 032 Floating components 033 Changes from action 020 - renaming properties 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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DFDL Specification V1 draft 034 available
by Alan Powell 14 May '09

14 May '09

Draft 34 of the OGF DFDL Specification v1 is available at https://forge.gridforum.org/sf/go/doc15632?nav=1 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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