In the WG call today for action 174 we decided to make both 'endOfParent' and the expression language optional, giving:

Feature	Detection
Text representation for types other than String	dfdl:representation="text" for Number, Calendar or Boolean types
Delimiters	dfdl:separator <> "" or dfdl:initiator <> "" or dfdl:terminator <> "" or dfdl:lengthKind="delimited"
BCD calendars	dfdl:binaryCalendarRep="bcd"
Multiple schemas	xs:include or xs:import in xsd
Named Formats	dfdl:defineFormat or dfdl:ref
Choices	xs:choice in xsd **
Arrays where size not known in advance	dfdl:occursCountKind 'implicit', 'parsed', 'stopValue' **
Expressions	Use of an expression in any property value
End of parent	dfdl:lengthKind ="endOfParent"

Errata will be added.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: Suman Kalia <kalia@ca.ibm.com>
Cc: dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org, Steve Hanson/UK/IBM@IBMGB
Date: 28/05/2012 02:07
Subject: Re: [DFDL-WG] Action 174: Making DFDL implementations easier

I tend to agree that really restricted path expressions seem easier to me than variables both conceptually and implementation wise.

On May 27, 2012 8:34 PM, "Suman Kalia" <kalia@ca.ibm.com> wrote:
I wonder if variables will make the implementation simpler; set only once semantics, scoping and namespace rules etc will be equally difficult to implement. With XPath tools and runtime support freely and easily available, I might be inclined towards using expressions instead of variables.. It would be worth checking with other implementers and get their opinion..

Suman Kalia
IBM Canada Lab
WMB Toolkit Architect and Development Lead
Tel: 905-413-3923 T/L 313-3923
Email: kalia@ca.ibm.com

For info on Message broker
http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html

From: Steve Hanson <smh@uk.ibm.com>
To: dfdl-wg@ogf.org,
Date: 05/25/2012 12:41 PM
Subject: Re: [DFDL-WG] Action 174: Making DFDL implementations easier
Sent by: dfdl-wg-bounces@ogf.org

Interesting, but there's a problem - variables are currently an optional feature! You could swap variables for paths, which is what I think Mike proposed in an earlier mail?

exprSubset = / | / exprList
atom = . | .. | identifier
exprList = atom | atom / exprList

That's essentially equivalent to what MRM provides for its 'repeat reference' and 'length reference' properties.

It doesn't handle things like an array count being 0 based, where you need the ability to add 1 to the result. And you can't do a simple comparison, which would make it easy to add choices and discriminators to an implementation. The trouble is that once you add in operators and literals you've pulled in a lot of the language.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Tim Kimber/UK/IBM
To: Mike Beckerle <mbeckerle.dfdl@gmail.com>
Cc: dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org, Steve Hanson/UK/IBM@IBMGB
Date: 25/05/2012 14:29
Subject: Re: [DFDL-WG] Action 174: Making DFDL implementations easier

My current thinking is:
- Minimum expression language is a simple variable reference. e.g. {$myLength} or {$myParentStructureLength}.
- That would require the ability to declare DFDL variables, set them, read them and put them into and out of scope. And restore their value after backtracking if backtracking is supported in the implementation.
This would make all the XPath functions optional, and would also make it unnecessary to use an XPath query engine.

regards,

Tim Kimber, Common Transformation Team,
Hursley, UK
Internet: kimbert@uk.ibm.com
Tel. 01962-816742
Internal tel. 246742

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: Steve Hanson/UK/IBM@IBMGB
Cc: Tim Kimber/UK/IBM@IBMGB, dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org
Date: 25/05/2012 13:58
Subject: Re: [DFDL-WG] Action 174: Making DFDL implementations easier

But the expression language is highly restricted in the subset.

On Fri, May 25, 2012 at 7:59 AM, Steve Hanson <smh@uk.ibm.com> wrote:
Tim

I tend to agree with endOfParent as optional.

Expression language was kept in the core to handle occursCountKind 'expression' which is also in the core. The examples of binary data we have seen from NSA and ESA both have occurs counts in the data, in the same way as COBOL does. When you have untagged binary data, it's typically the way to provide an array size. It was felt that dropping this from the core did left us with too little capability.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

From: Tim Kimber/UK/IBM
To: Steve Hanson/UK/IBM@IBMGB
Cc: dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org
Date: 25/05/2012 10:07
Subject: Re: [DFDL-WG] Action 174: Making DFDL implementations easier

1) I would make endOfParent an optional feature - there are not many formats that require it.

3) There are many formats that do not require the expression language - it is only required when a property value or an assert/discriminator needs to query already-parsed data. On that basis, I think the entire expression language feature should be optional.

regards,

Tim Kimber, Common Transformation Team,
Hursley, UK
Internet: kimbert@uk.ibm.com
Tel. 01962-816742
Internal tel. 246742

From: Steve Hanson/UK/IBM@IBMGB
To: dfdl-wg@ogf.org
Date: 25/05/2012 00:08
Subject: [DFDL-WG] Action 174: Making DFDL implementations easier
Sent by: dfdl-wg-bounces@ogf.org

Agreed on list, just need to answer questions 1) and 3) below.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 23/05/2012 18:21 -----

From: Steve Hanson/UK/IBM
To: dfdl-wg@ogf.org
Date: 15/05/2012 09:55
Subject: Making DFDL implementations easier

Please see below for a proposal to make an additional set of DFDL features optional. The goal is to make it considerably easier to create a minimal conforming DFDL processor for binary data.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 11/05/2012 12:50 -----

Feature	Detection
Text representation for types other than String	dfdl:representation="text" for Number, Calendar or Boolean types
Delimiters	dfdl:separator <> "" or dfdl:initiator <> "" or dfdl:terminator <> "" or dfdl:lengthKind="delimited"
BCD calendars	dfdl:binaryCalendarRep="bcd"
Multiple schemas	xs:include or xs:import in xsd
Named Formats	dfdl:defineFormat or dfdl:ref
Choices	xs:choice in xsd **
Arrays where size not known in advance	dfdl:occursCountKind 'implicit', 'parsed', 'stopValue' **
Advanced expressions	Advanced features of the DFDL expression language (tbd)

** Including one of these features mean that speculative parsing is needed.

Remaining questions:

1) What about lengthKind 'endOfParent' ?
2) Is leaving out choices too restrictive?
3) Expression language subset

The result is that a minimal conformant DFDL implementation just needs to support the following annotations and properties, and does not need speculative parsing.

dfdl:element
dfdl:sequence
dfdl:format

byteOrder
encoding
utf16width
alignment
alignmentUnits (bytes)
fillByte
leadingSkip
trailingSkip
lengthKind (explicit, implicit)
length
lengthUnits (bytes, characters)
representation (binary)
textPadKind
textTrimKind
textStringJustification
textStringPadCharacter
truncateSpecifiedLengthString
decimalSigned
binaryNumberRep
binaryVirtualDecimalPoint
binaryFloatRep (ieee)
binaryBooleanTrueRep
binaryBooleanFalseRep
binaryCalendarRep (binarySeconds, binaryMilliseconds)
binaryCalendarEpoch
sequenceKind (ordered)
occursCountKind (fixed, expression)
occursCount

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848

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

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 -- dfdl-wg mailing list
dfdl-wg@ogf.org
https://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

--
dfdl-wg mailing list
dfdl-wg@ogf.org
https://www.ogf.org/mailman/listinfo/dfdl-wg

--
Mike Beckerle | OGF DFDL WG Co-Chair
Tel: 781-330-0412

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-- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg

--
dfdl-wg mailing list
dfdl-wg@ogf.org
https://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