Open Grid Forum: Data Format Description Language Working Group OGF DFDL Working Group Call, September 29 2010 Attendees Stephanie Fetzer (IBM) Steve Hanson (IBM) Alan Powell (IBM) Tim Kimber(IBM) Apologies Mike Beckerle (Oco) Suman Kalia (IBM) Bob McGrath (National Center for Supercomputing Applications) Alejandro Rodriguez (National Center for Supercomputing Applications) 1. Current Actions Updated Below 2. textNumberRoundingMode. 29/09: The interaction between textNumberRoundingMode and the rounding number in the numberPattern is not clearly described. It was agreed to make textNumberRoundingMode the controlling switch and add 'none' to the enumerations. 3. Syntax of assert/discriminator 29/09: Alan suggested that the value form of assert/discriminator be made the same as the element form of representation properties. Steve felt that they were not the same as format properties (eg they can have defaults) so should not have the same syntax. Agreed there will be a new property dfdl:testKind 'expression' 'pattern' Meeting closed, 16:35 Next call Wednesday 06 October 2010 15:00 UK (10:00 ET) Next action: 123 Actions raised at this meeting No Action 121 2. textNumberRoundingMode. 29/09: The interaction between textNumberRoundingMode and the rounding number in the numberPattern is not clearly described. It was agreed to make textNumberRoundingMode the controlling switch and add 'none' to the enumerations. Closed 122 Syntax of assert/discriminator 29/09: Alan suggested that the value form of assert/discriminator be made the same as the element form of representation properties. Steve felt that the assert attributes were not the same as format properties (eg they can have defaults) so should not have the same syntax. Agreed there will be a new property dfdl:testKind 'expression' 'pattern' Closed Current Actions: No Action 066 Investigate format for defining test cases 25/11:IBM to see if it is possible to publish its test case format. 04/12: no update ... 17/02: IBM is willing in principle to publish the test case format and some of the test cases. May need some time to build a 'compliance suite' 24/03: No progress 03/03: Discussions have been taking place on the subset of tests that will be provided. 10/03: work is progressing 17/03: work is progressing 31/03: work is progressing 14/04: And XML test case format has been defined and is being tested. 21/04. Schema for TDML defined. Need to define how this and the test cases will be made public 05/05: Work still progressing 12/05: Work still progressing 02/06: Work still progressing on technical and legal considerations ... 25/08: Will chase to allow Daffodil access to test cases. The WG should define how implementation confirm that they 'conform to DFDL v1' 01/09: IBM still progressing the legal aspect. Intends to publish 100 or so tests as soon as it can, ahead of a full compliance suite. 08/09: IBM still progressing 15/09: IBM still progressing, expect tests to be available within a few weeks 22/09: IBM still progressing, expect tests to be available within a few weeks 29/09:Test cases are being prepared. 085 ALL: publicise Public comments phase to ensure a good review.. 14/04: see minutes 21/04: Press release, OMG and other standards bodies. 05/05: Alan and Steve H have contacted other standards bodies. Will ask them to add comments on spec 15/05: still no public comments 02/06: No public comments 16/06: Public comments period has ended with no external comments. Alan had posted changes made in draft 041. Steve suggested send a note to the WG highlighting these changes. Steve also suggested requesting an extension as other IBM groups may review. We discussed whether this was necessary as changes will need to be made during the implementation phase anyway. Alan to ask OGF what the process is for changes post public comment. 23/06: Still no comments. Alan will contact OGF to understand the rest of the process. 30/06: Alan has emailed Joel asking what the process is now public comment period is over and can we update the published version with WG updates. No response yet. 07/07: No response. Alan will chase up 14/07: No response from Joel. Sent email to Greg Newby by no response. 21/07: Still no response. 04/08: Joel has responded that it is up to the WG to decide if the changes are significant enough to need additional review. Alan to contact David Martin and Erwin Laure for guidance if we split the specification. 11/08: Received a response from Joel that the WG can decide if a re- public review is necessary before becoming a 'proposed recommendation'. Alan responded that the WG agreed that a re-review was not necessary. The next stage is for OGF review committee to approve publication. 11/08: Specification is now 'awaiting author changes' before being submitted to the OGF technical committee for approval as a 'proposed specification'. Alan would like to have the updated specification complete by Sept 10th. The WG needs to complete all actions by then or decide that they do not need to be included in this phase of the process. 01/09: Alan and Steve have discussed and propose Sept 30th for completion of draft 43 and closure of all actions. 08/09: Target for completion September 30. 15/09: as above 22/09: as above 29/09: Draft 43 will be published this week for WG review prior to submitting to OGF 111 Daffodil DFDL parser 11/08: Bob and Alejandro described the new implementation that they have developed. It is a new code base and is not based on the Deffudle prototype. It is written in scala and implements approximately 80% of the features in the public comments draft of DFDL V1. Alejandro will send a list of the features not implemented. We discussed the scenarios that motivated the development which was to extract data from various sources and transform into canonical formats. Bob offered to make Daffodil available for the WG to assess the functionality. IBM WG members will get approval the company to allow them to receive Daffodil. Bob raised the question that if Daffodil becomes the public implementation of DFDL then we will need to work out how that would be funded and managed. It would be helpful if IBM test cases were available to Daffodil. IBM will investigate 25/08: Alejandro had sent a list of the functions that he has implemented and Steve ahd responding indicating the extra functions he thought were essential. Since then Alejandro has implemented some of the missing functions, such as escape schemes, pre-defined variables, binary decimal numbers, etc, and will update his list. Bob is planning to make the parser available on the internet to allow testing. His organisation is being reorganised and he doesn't know what the priority of Daffodill will be so it is essential that we move quickly. It would help if IBM could indicate its support for Daffodil in some semi-formal way. 01/09: Alejandro updating Daffodil to include escape schemes, unordered sequences and ignoreCase. Daffodil being placed under formal source control in anticipation of external release. Bob has a start October deadline to create a report on what has been done for his sponsors. It would be great if we could get Daffodil on the web and have run some IBM tests so it could be highlighted at OGF 30 at end October. 08/09: Alejandro is marking up Spec draft 42 to indicate which features Daffodil implement. Bob expects Daffodil to be available on the web soon. 15/09: Alejandro had indicated in the specification which functions were implemented in Daffodill. Steve had reviewed and identified which function need to be implemented and which could be considered optional (see action 099). Alejandro is implementing the missing core functions. There was some discussion about the limitations on unordered groups. (stop value and expression not supported). It was agreed that it should be a schema definition error if dfdl:occursCountKind is 'stopValue' on any element within an unordered sequence and a floating element. 22/09: not discussed 29/09: not discussed 112 DFDL certification process 25/08: Discussed how to certify DFDL implementations. Alan to investigate if OGF have a defined process. 01/09: In progress, spec needs to state what conformance means, as part of this work 08/09: Discussed what needs to be said in the spec and agreed that details of a conformance test suite should be in another document. Alan to draft conformance section. 15/09: Alan had look at the conformance sections in XML and Schema specifications both of which indicate sections which must be implemented. None just say 'execute the test suite'. They talk in terms of conformance of document, schema and processors.. 22/09: no progress 22/09: Alan has added short Conformance and Optional Features sections to spec which was briefly discussed. Discussed naming for processors that don't implement optional features and those that implement all features. 114 OGF 30 25/08: OGF30 takes place on October 25-29 in Brussels. Should we have a WG session? 09/01: Given emergence of NCSA implementation and spec completion target of 30th Sept it makes sense to host a session at OGF 30. 08/09: Steve to request permission to go 15/09: Travel request has be submitted 22/09: DFDL session is scheduled at 11:00am Monday Oct 25th. Closed actions No Action 107 teston/testoff dfdl expression functions. Are these functions still needed. They were introduced to allow individual bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that use existence flags to see if they are still required. 04/08: Not discussed 11/08: Not discussed 25/08: Not discussed 01/09: Steve to progress by Sept 30th 08/09: Steve to progress by Sept 30th 15/09: The ISO 8583 standard has existence flags at the beginning that are encoded so cannot be defined as an array of bits. Therefore DFDL needs the ability to set individual bits within an unsigned int. However the functions, particualry SetOn/Off, as currently defined are not correct. SetOn returns a byte with the relevant bit set on. This must then be combined with other bytes which isn't very usable. Steve to circulate example of use and suggested improvements. 22/09: Steve had documented the why the functions were required to parse ISO 8583 messages. He had suggested the following improvements xs:boolean dfdl:testBit(xs:unsignedByte, xs:unsignedByte) Returns Boolean true if the bit number given by arg #2 is set on in the byte given by arg #1, otherwise returns Boolean false. xs:unsignedByte dfdl:setBits(xs:boolean+) Returns an byte being the value of the bit positions provided by the Boolean arguments, where true=1, false=0. The # of args must 8. Note that the bit numbering goes from left to right, in accordance with section 12.3.7.2 of the spec. The type was changed from unSignedLong to unSignedByte to avoid problems with padding when not enough bits are provided. 29/09: Syntax agreed. Some errors in existing function descriptions need fixing. Closed 118 2. Rules for 'missing' elements lengthKind='implicit' and xs:maxLength or xs:length is "0": element is missing lengthKind='implicit' and length is not "0": element is missing if it has an initiator AND emptyValueDelimiterPolicy excludes the initiator AND the initiator is not found in the data ( regardless of discriminators or initiatedContent ) lengthKind='explicit' and length is an expression : element is missing if the expression evaluates to zero. lengthKind='explicit' and length is "0": element is missing lengthKind='explicit' and length is not "0": element is missing if it has an initiator AND emptyValueDelimiterPolicy excludes the initiator AND the initiator is not found in the data ( regardless of discriminators or initiatedContent ) lengthKind='pattern' : element is missing if the length of the pattern match is zero lengthKind='prefixed' : element is missing if the prefixed length region parses as zero lengthKind='delimited' and delimiterPolicy='suppressed' and the end of the group has not been encountered : element is missing if it has an initiator AND emptyValueDelimiterPolicy excludes the initiator AND the initiator is not found in the data ( regardless of discriminators or initiatedContent ) lengthKind='delimited' and delimiterPolicy='suppressed' or 'suppressedAtEnd' and the end of the group has been encountered : element is missing lengthKind='delimited', all other cases : element is missing if its scanned length is zero lengthKind='endOfParent': element is missing if its scanned length is zero It is a schema definition error to specify emptyValueDelimiterPolicy 'initiator' for lengthKind 'explicit' or 'implicit'. 22/09: We discussed if these rules could be simplified to say an element is missing if it's initiator is missing or its content region is empty. Need further discussion. 22/09: Tim suggested simplifying the above rules with An element is missing 1. if it has an initiator AND emptyValueDelimiterPolicy excludes the initiator AND the initiator is not found in the data 2. else if the content region is empty Also: It is a schema definition error if a sequence has 'initiated content and one of its children has emptyValueDelimiterPolicy or nilValueInitiatorPolicy set to 'none' or 'terminator'. It is a schema definition error to specify emptyValueDelimiterPolicy 'initiator' or 'both' for lengthKind 'explicit' or 'implicit'. Closed 119 In passing we noted that the position of the prefix length relative to the initiator was not defined in the grammar and whether the prefix could have an initiator and terminator. Need further discussion 22/09: The prefix length region is between the initiator and the content region ( leftFraming prefixLengthRegion simple/complexContent) The simpleType for the length prefix can specify any dfdl property with the exception of lengthKind 'prefixed' and 'endOfParent' Closed Work items: No Item target version status 005 Improvements on property descriptions not started 012 Reordering the properties discussion: move representation earlier, improve flow of topics not started 036 Update dfdl schema with change properties ongoing 042 Mapping of the DFDL infoset to XDM none not required for V1 specification 070 Write DFDL primer 071 Write test cases. 083 Implement RFC2116 109 Add 'message' attribute to dfdl:discriminator 01/09: Closed: Conclusion was that this is genuinely useful, and has low implementation cost. Will add a 'message' attribute to dfdl:discriminator. 43 110 Clarify expression limitations for defineVariable, newVariableInstance and setVariable 01/09: Closed: Spec should distinguish newVariableInstance defaultValue from setVariable value. For newVariableInstance defaultValue, disallow downward references and references to self (must be usable from the point of declaration) For setVariable allow downward references and references to self, and always evaluate at end of component. (defineVariable defaultValue should be same as newVariableInstance) 43 113 Be specific about regular expression syntax 43 108 Updates to hidden mechanism 43 99 Updates to reflect subsetting and unparser optionality 43 112 Define what conformance to spec means 43 115 Clarify allowed lengths for signed binary integers 43 116 2. xs:minLength The spec currently states When an element declaration specifies a default value, and has type xs:string, then xs:minLength must be specified and must be 1 or greater. It is a schema definition error otherwise. The process for defaults and nils means this restriction is no longer needed. Agreed 43 117 3. Is UTF-16 a fixed width or variable width encoding Proposal -UCS2 is a fixed length encoding -UTF-16 is a variable width encoding. - A new property dfdl:UTF16Fixed 'yes ¦ no' treat UTF-16 as a fixed width encoding 15/09: Closed 43 118 2. Document that an empty sequence that is the content of complex type is ignored even when it has annotations It is a schema definition error if an empty sequence is the content of a complex type 43 099 Splitting the specification in simpler sections. 22/09: We reviewed the proposed list of optional features and approved. These will be documented by adding a section that lists these features rather than making them inline. It will be closely related to the conformance section.. Closed 43 101 Semantics of 'fixed' Proposal: - xs:fixed will not be used for parsing but only for validation and for providing a default value on unparsing. - A new dfdl function will be defined that applies only to simple element and tests whether the element exists including applying all the schema facets and other constraints. 22/09: Discussed whether dfdl:checkConstaints should included exists function. It isn't obvious what the return code should be for elements that don't exist. checkConstarints will check that element does exist. 'true' means the element exists and is valid, 'false' means doesn't exist or exists but doesn't meet constraints. The parameter is a path to a simple or complex element. If complex and it exists return 'true' Closed 43 108 dfdl:hidden Global group approach Summary: Particle to hide can be a local element, element ref, local sequence, local choice or group ref Particle is removed from its parent into a dedicated global group of composition sequence and replaced in the parent by a new empty local sequence The new empty local sequence carries a dfdl:hiddenGroupRef property, other DFDL properties are not allowed Pros: Removal of all DFDL annotations and use of the resultant pure XSD results in same infoset Global group can be reused Cons: Making something hidden is a refactor operation Global group sequence needs DFDL properties setting correctly Alejandro had implemented extensions to the hidden function. 1. Allow hidden sequence to reference a global element. Decided against as Suman had identified some problems with namesapces. 2. Allow the reference global group to contain a choice in addition to a sequence. It was agreed this was a useful extension. 22/09: Closed 43 113 Regular Expressions. 15/09: Agreed that should just say that either JAva or PERL regular expressions can be used and for portability the common subset of functions should be used. 22/09: Closed 43 113b Regular Expressions for Assert/Discriminator. Allowed as alternative to expression on dfdl:assert and dfdl:discriminator Pattern may be specified as attribute or element value Attribute: new testPattern attribute Element value: braces ( ) indicate pattern instead of expression 15/09: Do not need the braces as expressions start with '{'. Need to state rules for where the patter matching starts in the data stream. 22/09: Closed 43 115 Clarify allowed lengths for signed integer types when rep is binary integer (ie, two's complement) 01/09: No technical reason to restrict lengths to 2^x bytes, could be odd, could be bits. But rare in practise so if we do relax, limit any core subset to 2^x bytes. 22/09: Agreed that there should be not restrictions on lengths. Closed 43 107 teston/testoff dfdl expression functions. 22/09: Steve had documented the why the functions were required to parse ISO 8583 messages. He had suggested the following improvements xs:boolean dfdl:testBit(xs:unsignedByte, xs:unsignedByte) Returns Boolean true if the bit number given by arg #2 is set on in the byte given by arg #1, otherwise returns Boolean false. xs:unsignedByte dfdl:setBits(xs:boolean+) Returns an byte being the value of the bit positions provided by the Boolean arguments, where true=1, false=0. The # of args must 8. Note that the bit numbering goes from left to right, in accordance with section 12.3.7.2 of the spec. The type was changed from unSignedLong to unSignedByte to avoid problems with padding when not enough bits are provided. 29/09: Syntax agreed. Some errors in existing function descriptions need fixing. Closed 118 2. Rules for 'missing' elements 22/09: Tim suggested simplifying the above rules with An element is missing 1. if it has an initiator AND emptyValueDelimiterPolicy excludes the initiator AND the initiator is not found in the data 2. else if the content region is empty Also: It is a schema definition error if a sequence has 'initiated content and one of its children has emptyValueDelimiterPolicy or nilValueInitiatorPolicy set to 'none' or 'terminator'. It is a schema definition error to specify emptyValueDelimiterPolicy 'initiator' or 'both' for lengthKind 'explicit' or 'implicit'. Closed 119 In passing we noted that the position of the prefix length relative to the initiator was not defined in the grammar and whether the prefix could have an initiator and terminator. Need further discussion 22/09: The prefix length region is between the initiator and the content region ( leftFraming prefixLengthRegion simple/complexContent) The simpleType for the length prefix can specify any dfdl property with the exception of lengthKind 'prefixed' and 'endOfParent' Closed 121 2. textNumberRoundingMode. 29/09: The interaction between textNumberRoundingMode and the rounding number in the numberPattern is not clearly described. It was agreed to make textNumberRoundingMode the controlling switch and add 'none' to the enumerations. 43 122 Syntax of assert/discriminator 29/09: Alan suggested that the value form of assert/discriminator be made the same as the element form of representation properties. Steve felt that the assert attributes were not the same as format properties (eg they can have defaults) so should not have the same syntax. Agreed there will be a new property dfdl:testKind 'expression' 'pattern' Regards Alan Powell Development - MQSeries, Message Broker, ESB IBM Software Group, Application and Integration Middleware Software ------------------------------------------------------------------------------------------------------------------------------------------- IBM MP211, Hursley Park Hursley, SO21 2JN United Kingdom Phone: +44-1962-815073 e-mail: alan_powell@uk.ibm.com Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU