"Actually, the target of the indirection is just like an element or model-group, except without alignment regions. Ugly to have to repeat the whole grammar for that. ". Correct, and I haven't. My changes are for the indirection value, not the target. We have to handle 'indirectionUnusedValue' and reflect that initiator & terminator do not apply. Regards Steve Hanson IBM Hybrid Integration, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 Note: I work Tuesday to Friday From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: Steve Hanson <smh@uk.ibm.com> Cc: Bradd Kadlecik <braddk@us.ibm.com>, DFDL-WG <dfdl-wg@ogf.org> Date: 24/07/2020 13:59 Subject: [EXTERNAL] Re: [DFDL-WG] DFDL pointer & offset proposal Actually, the target of the indirection is just like an element or model-group, except without alignment regions. Ugly to have to repeat the whole grammar for that. Perhaps we can get away with just documenting that the alignment regions must be zero length when target of an indirection? I did not try to put this modified grammar into my commented copy of the proposal (attached). The "connection" to the indirect pointer or offset is not something that the grammar can express. Attached * my review (with new comments that start with "V4:"), * my first cut of a DFDL schema for TIFF v6.0, * a copy of the TIFF v6.0 spec. I wasn't actually able to pull off TIFF. Comments in the schema discuss why, which is due to TIFF being a linked list, and I'm not able to terminate the chain. There's maybe a trick using negative offsets, but I don't want to consider that yet, as those are entirely problematic. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | www.owlcyberdefense.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Fri, Jul 24, 2020 at 7:03 AM Steve Hanson <smh@uk.ibm.com> wrote: Bradd, Mike - as discussed on WG call please review my version of the grammar for next call. The key issue is how to link the target of the indirection into the main grammar, as it is dis-contiguous. Regards Steve Hanson IBM Hybrid Integration, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 Note: I work Tuesday to Friday From: Bradd Kadlecik/Poughkeepsie/IBM To: Steve Hanson/UK/IBM Cc: DFDL-WG <dfdl-wg@ogf.org>, "dfdl-wg" <dfdl-wg-bounces@ogf.org>, Mike Beckerle <mbeckerle.dfdl@gmail.com> Date: 23/07/2020 14:52 Subject: Re: [EXTERNAL] Re: [DFDL-WG] DFDL pointer & offset proposal I incorporated some of your grammar changes but had a few modifications of my own we can discuss further in case I'm not understanding some of the subtleties. I think there may be a case for a nil value with indirection however as well. I've updated the document to include the changes as version 4. Regards, Bradd Kadlecik z/TPF Development Phone: 1-845-433-1573 E-mail: braddk@us.ibm.com 2455 South Rd Poughkeepsie, NY 12601-5400 United States From: Steve Hanson/UK/IBM To: Bradd Kadlecik/Poughkeepsie/IBM@IBMUS Cc: DFDL-WG <dfdl-wg@ogf.org>, "dfdl-wg" <dfdl-wg-bounces@ogf.org>, Mike Beckerle <mbeckerle.dfdl@gmail.com> Date: 07/10/2020 08:11 AM Subject: Re: [EXTERNAL] Re: [DFDL-WG] DFDL pointer & offset proposal I think 'indirect' in property names should be 'indirection', so I will assume that in what follows. I am not happy with 'indirectionEmptyValue' or 'indirectionMissingValue'. Both 'empty' and 'missing' are concepts with well-defined meanings in DFDL. How about 'indirectionInactiveValue' or better 'indirectionUnusedValue'? My stab at an updated grammar below (changes in blue). There is no concept of an empty indirection value or a nil indirection value, so we don't need those clauses. I also think we can simplify the EnclosedElement construct (changes in red ) Bradd I know you were struggling with how to link the target of the indirection into the main grammar, as it is dis-contiguous. I think we can achieve that by incorporating the target(s) into the Document as a whole. If we think that the concept of an indirection can only ever happen inside a complex type, then we could move IndirectionRep from SimpleElement/ComplexElement to EnclosedElement. I don't think it is worth getting more specific with IndirectElement. Specifically, it has no LeadingAlignment or TrailingAlignment, but to reflect that requires duplicating most of the rest of the grammar. You have not disallowed lengthKind 'prefixed' for the 'indirectionType', so that is included in the grammar. Productions Document = DocumentElement IndirectElement* DocumentElement = SimpleElement | ComplexElement SimpleElement = SimpleLiteralNilElementRep | SimpleEmptyElementRep | SimpleNormalRep | IndirectionRep SimpleEnclosedElement = SimpleElement | AbsentElementRep ComplexElement = ComplexLiteralNilElementRep | ComplexNormalRep | ComplexEmptyElementRep | IndirectionRep ComplexEnclosedElement = ComplexElement | AbsentElementRep EnclosedElement = SimpleElement | ComplexElement | AbsentElementRep IndirectElement = SimpleElement | ComplexElement AbsentElementRep = Absent IndirectionRep = IndirectionLeftFraming PrefixLength IndirectionContent IndirectionRightFraming IndirectionLeftFraming = LeadingAlignment IndirectionRightFraming = TrailingAlignment IndirectionContent = LeftPadding [ IndirectionValue | IndirectionUnusedValue ] RightPadOrFill IndirectionValue = SimpleValue SimpleEmptyElementRep = EmptyElementLeftFraming EmptyElementRightFraming ComplexEmptyElementRep = EmptyElementLeftFraming EmptyElementRightFraming EmptyElementLeftFraming = LeadingAlignment EmptyElementInitiator PrefixLength EmptyElementRightFraming = EmptyElementTerminator TrailingAlignment SimpleLiteralNilElementRep = NilElementLeftFraming [NilLiteralCharacters | NilElementLiteralContent] NilElementRightFraming ComplexLiteralNilElementRep = NilElementLeftFraming NilLiteralValue NilElementRightFraming NilElementLeftFraming = LeadingAlignment NilElementInitiator PrefixLength NilElementRightFraming = NilElementTerminator TrailingAlignment NilElementLiteralContent = LeftPadding NilLiteralValue RightPadOrFill SimpleNormalRep = LeftFraming PrefixLength SimpleContent RightFraming ComplexNormalRep = LeftFraming PrefixLength ComplexContent ElementUnused RightFraming LeftFraming = LeadingAlignment Initiator RightFraming = Terminator TrailingAlignment PrefixLength = SimpleContent | PrefixPrefixLength SimpleContent PrefixPrefixLength = SimpleContent SimpleContent = LeftPadding [ NilLogicalValue | SimpleValue ] RightPadOrFill ComplexContent = Sequence | Choice Sequence = LeftFraming SequenceContent RightFraming SequenceContent = [ PrefixSeparator EnclosedContent [ Separator EnclosedContent ]* PostfixSeparator ] Choice = LeftFraming ChoiceContent RightFraming ChoiceContent = [ EnclosedContent ] ChoiceUnused EnclosedContent = [ EnclosedElement | Array | Sequence | Choice ] Array = [ EnclosedElement [ Separator EnclosedElement ]* [ Separator StopValue] ] StopValue = SimpleElement LeadingAlignment = LeadingSkip AlignmentFill TrailingAlignment = TrailingSkip RightPadOrFill = RightPadding | RightFill | RightPadding RightFill Regards Steve Hanson IBM Hybrid Integration, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 Note: I work Tuesday to Friday From: Bradd Kadlecik/Poughkeepsie/IBM To: Steve Hanson/UK/IBM Cc: DFDL-WG <dfdl-wg@ogf.org>, "dfdl-wg" <dfdl-wg-bounces@ogf.org>, Mike Beckerle <mbeckerle.dfdl@gmail.com> Date: 09/07/2020 15:09 Subject: Re: [EXTERNAL] Re: [DFDL-WG] DFDL pointer & offset proposal I have updated the document proposal with proposed DFDL grammar changes: [attachment "DFDL_Indirection_v3.docx" deleted by Bradd Kadlecik/Poughkeepsie/IBM] Regards, Bradd Kadlecik z/TPF Development Phone: 1-845-433-1573 E-mail: braddk@us.ibm.com 2455 South Rd Poughkeepsie, NY 12601-5400 United States 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