On Wed, Jun 17, 2009 at 6:37 AM, Alan Powell <alan_powell@uk.ibm.com> wrote:

Mike

I think you have prefix/postfix separator in the wrong place

You definition has  LeadingAlignment Initiator Prefixseparator and it should be Prefixseparator  LeadingAlignment Initiator so

LeftSequenceFraming = Prefix PrefixSeparator should be LeftSequenceFraming = PrefixSeparator Prefix

Similarly for postfix.


Also I don't think ChoiceUnresolvableItem = OpaqueTypeContent is correct.
Unresolveable choice content is the same as resolvable choice content as you need to be able to work out the length of the choices (which must be the same).  


I have change AlignmentPad to AlignmentFill as the pad character is not used during alignment

Small stylistic comment: Should LeftPadding be just Padding and RightPadorFill be just PadorFill?


Alan Powell

MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
Notes Id: Alan Powell/UK/IBM     email: alan_powell@uk.ibm.com  
Tel: +44 (0)1962 815073                  Fax: +44 (0)1962 816898

From:	Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:	Steve Hanson/UK/IBM@IBMGB, Alan Powell/UK/IBM@IBMGB
Date:	11/06/2009 03:23
Subject:	please review revised DFDL grammar

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I'll take this to the broader group once you guys have had a look at this.

Please review this revised grammar table. I've tried to include the necessary pieces to handle padding on left and padding or fill on right, and in a manner consistent with our most recent policies where dfdl:length for complex types can only be on the element itself, not any model group.

I am uncertain if this grammar has enough features to capture everything about say, CalendarTypeContent. E.g., are there no properties about framing that are special to calendars? This grammar suggests that padding/fill is all handled outside the content for calendars, as for all simple types.

I also added prefix/postfix separators back in. (We excised them a while back, but I'm pretty sure decided to put them back in.)

The issue about proper interpretation of leading and trailing skip bytes is outstanding still.

There are no changes to the simple content grammar. I'm including it here for making this message self-contained.

I believe that the blowout pictures in the grammar section are to some degree outliving their usefulness. They are in essence equivalent to this grammar. By arranging the grammar to use the terms left framing, right framing, and content, I believe the information about what start of content is, vs. start of item can be defined without most of the pictures. I think the one which defines item start, content start, content end, and item end is useful. The others not so useful.

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First we present the simple content types.

Production	See Section(s)
SimpleContent = NumberTypeContent | StringTypeContent | CalendarTypeContent | BooleanTypeContent | OpaqueTypeContent
NumberTypeContent = TextNumber | BinaryIntegerNumber | BinaryFloatNumber	TBD
StringTypeContent = TextString	TBD
CalendarTypeContent = TextCalendar | BinaryIntegerCalendar	TBD
BooleanTypeContent = TextBoolean | BinaryIntegerBoolean	TBD
OpaqueTypeContent =  BinaryOpaque	TBD

 

There are additional NumberTypeContent terminals specified in the DFDL specification supplements (for bcd, zoned and packed decimal).

These simple types are the basic data content pieces found in DFDL-described data sources.

The rest of this grammar describes how these basic pieces are composed into arrays and more complex types.

 

Productions
Document = Element
Element = SimpleElement | ComplexElement SimpleElement =  LeftSimpleFraming SimpleContent RightFraming ComplexElement = LeftComplexFraming ComplexContent RightFraming LeftSimpleFraming = Prefix LeftPadding LeftComplexFraming = Prefix RightFraming = RightPadOrFill  Suffix
ComplexContent = Sequence | Choice
Sequence = LeftSequenceFraming SequenceContent RightSequenceFraming SequenceContent = [ SequenceItem [ Separator SequenceItem ]* ]   SequenceItem = Element | Array | ComplexContent LeftSequenceFraming = Prefix PrefixSeparator RightSequenceFraming = PostfixSeparator Suffix
Choice = LeftChoiceFraming ChoiceContent RightChoiceFraming ChoiceContent = ChoiceResolvableItem | ChoiceUnresolvableItem[MJB1]  ChoiceResolvableItem = Element | Array | ComplexContent ChoiceUnresolvableItem = OpaqueTypeContent[MJB2]  LeftChoiceFraming = Prefix RightChoiceFraming = Suffix
Array = [ Element [ Separator Element ]*  [ Separator StopValue] ] StopValue = SimpleElement
Prefix = LeadingAlignment Initiator Suffix = Terminator TrailingAlignment
LeadingAlignment = LeadingSkipBytes AlignmentPad TrailingAlignment = TrailingSkipBytes

 

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