[DFDL-WG] DFDL pointer & offset proposal
Steve Hanson
smh at uk.ibm.com
Fri Jul 24 13:07:55 EDT 2020
"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 at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday
From: Mike Beckerle <mbeckerle.dfdl at gmail.com>
To: Steve Hanson <smh at uk.ibm.com>
Cc: Bradd Kadlecik <braddk at us.ibm.com>, DFDL-WG <dfdl-wg at 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 at 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 at 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 at ogf.org>, "dfdl-wg" <dfdl-wg-bounces at ogf.org>,
Mike Beckerle <mbeckerle.dfdl at 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 at us.ibm.com
2455 South Rd
Poughkeepsie, NY 12601-5400
United States
From: Steve Hanson/UK/IBM
To: Bradd Kadlecik/Poughkeepsie/IBM at IBMUS
Cc: DFDL-WG <dfdl-wg at ogf.org>, "dfdl-wg" <dfdl-wg-bounces at ogf.org>,
Mike Beckerle <mbeckerle.dfdl at 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 at 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 at ogf.org>, "dfdl-wg" <dfdl-wg-bounces at ogf.org>,
Mike Beckerle <mbeckerle.dfdl at 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 at 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
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