It was noted on the call this week that there is an alternative to my zoned decimal overpunching proposal i) below.

I said:

- If it is an unsigned type then DFDL expects the rightmost byte to have a zone nibble when parsing, and outputs a zone nibble when unparsing.
- If it is a signed type then DFDL expects it to have a sign nibble when parsing, and outputs a sign nibble when unparsing.

But my unsigned type behaviour could be achieved by specifying a rep of text instead of zoned.  If that is the case, the alternative is to only allow zoned rep for signed decimal logical types.

Thoughts?

Regards

Steve Hanson
Programming Model Architect
WebSphere Message Brokers
Hursley, UK
Internet: smh@uk.ibm.com
Phone (+44)/(0) 1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 05/02/2009 10:17 -----
Steve Hanson/UK/IBM

28/01/2009 13:54

To
DFDL Working Group
cc
Subject
DFDL OGF WG call - Action 020Link




Action 020:
020
SH: Resolve packedDecimalSignCodes behaviour depends on NumberCheckPolicy
22/10: No progress
10/12: added how to decide to overpunch and sign position


a) Resolve packedDecimalSignCodes behaviour depends on NumberCheckPolicy

Add new property to section 15.4 Properties Specific to Number with Binary representation.
binaryNumberCheckPolicy Enum

Values are “strict” and “lax”.

Indicates how lenient to be when parsing binary numbers.

If ‘lax” then the parser tolerates all valid alternatives where such alternatives exist. Specifically, for binaryNumberRepresentation = 'packed' the sign nibble for positive, negative, unsigned and zero is allowed to be any of the valid respective values.

On unparsing, the specified value is always used.



Also suggest changing some of the other property names in 15.4:
"decimalVirtualPoint" -> "binaryDecimalVirtualPoint"
"packedDecimalSignCodes" -> "binaryPackedSignCodes"

And changing binaryNumberRepresentation enumeration:
"BCD" -> "bcd"

b) Zoned decimals: How to decide to overpunch and sign position

Spec assumes that overpunching of the rightmost character always takes place. IBM architecture allows no overpunching (ie, Fx instead of Cx/Dx) - this is supported by IBM MRM & WTX parsers. Additionally IBM MRM parser allows separate sign byte, and sign byte on left. Let's deal with these separately:
i) No overpunching.
The IBM architecture allows the rightmost byte to have a zone (Fx) or a sign (Cx/Dx) as the left nibble. I don't see why we can't base what to expect when parsing, and output when unparsing, on the logical xsd type.
- If it is an unsigned type then DFDL expects the rightmost byte to have a zone nibble when parsing, and outputs a zone nibble when unparsing.
- If it is a signed type then DFDL expects it to have a sign nibble when parsing, and outputs a sign nibble when unparsing.
For analogy with DFDL packed decimals, it seems at first glance that we should also extend the numberCheckPolicy 'lax' setting to treat a zone nibble as a +ve sign nibble for a signed type. However, IBM iSeries always outputs Fx to mean +ve but accepts both Fx & Cx on input. It is perhaps better therefore that DFDL always tolerates Fx when parsing a signed zoned decimal, otherwise iSeries users would always have to set numberCheckPolicy to 'lax', which might have other implications in the future.
ii) Separate sign byte.
I don't believe the IBM architecture allows this. I'm not sure where MRM got this from. I don't think DFDL needs to support it.
iii) Sign byte on left.
I don't believe the IBM architecture allows this. I'm not sure where MRM got this from. I don't think DFDL needs to support it.

Conclusion: No new DFDL properties needed, but words need adding to explain zoned parse/unparse behaviour better.

Also suggest changing property names:
"zonedDecimalSignStyle" -> "numberZonedSignStyle"
"zeroNumberRep" -> "numberZeroRep"

Should also make clear that any explicit negative pattern in numberPattern will be ignored if the xsd type is unsigned. (We could make this an error but it precludes creation of a textNumberFormat that works with both signed and unsigned types, plus pattern  "##0.0" implictly is equivalent to "##0.0;(##0.0)" ).

Regards

Steve Hanson
Programming Model Architect
WebSphere Message Brokers
Hursley, UK
Internet: smh@uk.ibm.com
Phone (+44)/(0) 1962-815848


Alan Powell/UK/IBM@IBMGB
Sent by: dfdl-wg-bounces@ogf.org

23/01/2009 13:36

To
dfdl-wg@ogf.org
cc
Subject
[DFDL-WG] DFDL: Minutes from OGF WG call, 21 January 2009






Open Grid Forum: Data Format Description Language Working Group

Weekly Working Group Conference Call
14:00 GMT, 21 January 2009


Attendees
Alan Powell (IBM)
Mike Beckerle(Oco)

Apologies
Steve Hanson (IBM)


1. XSD 1.1
Deferred to next call

2. Calendar formats
Discussed updated (v4) supplement emailed by AP

Agreed millisec/secSinceEpoc cannot be implied by length of logical data so need seperate enumerations. Observed that these options were really combination of 3 properties  binary, length and sec/millisec.  Suggested renaming to binarySeconds and binaryMilliseconds

Packed calendars: decided that need to be able to specify at least the packedDecimalSignCodes property rather than assuming a default so reference will be added to calendar description

Locale needs to be specified  for numberformats and calendarFormats (didn't identify any other areas) as it modifies the behaviour of ICU. Decided to add  locale to numberFormat and CalendarFormat

3. Escape Schemes

Agreed need for multiple escape delimiter pairs but not nested.
Need an escape for escape character even though in most cases this will be the same character, eg /n //, There are some formats that have a different escape, eg /n &/. Only need single escape characters and one level of escape characters.
Discussed how to deal with comments of the form   /*  comment */  where the escape delimiters  are also the initiator and terminator of the field. Semantic needed is 'only look for field terminator not any parent terminator or any other syntax elements'. May fall out naturally from the speculative parsing rules. Need further discussion.

4. AOB
Next call 28 January 14:00

Meeting closed, 15:00 GMT

Actions raised at this meeting
No
Action
031

Current Actions:
No
Action
012
AP/SH: Update decimalCalendarScheme
10/9: Not allocated yet
17/9: No update
24/9: Add calendar binary formats to actions
22/10: No progress
16/1: proposal distributed and discussed. Will be redistributed
21/1: add locale,
020
SH: Resolve packedDecimalSignCodes behaviour depends on NumberCheckPolicy
22/10: No progress
10/12: added how to decide to overpunch and sign position
023
MB: Review Schema 1.1
024
String XML type
025
Escape schemes
21/1: discussed requirements
026
SH: Envelopes and Payloads
027
Property precedence tables
028
Variable markup
029
 valueCalc (output length calculation)
030
AP: confirm with WTX that can drop duration
21/6: WTX confirm that they do not have a duration type so do not need it in dfdl. Will drop from spec. Closed

Closed actions:
030
AP: confirm with WTX that can drop duration
21/6: WTX confirm that they do not have a duration type so do not need it in dfdl. Will drop from spec. Closed

034 Work items:
No
Item
001
String XML type (Ian P) - Apr 30, 2008
002
Escape schemes (Ian P) - Apr 30, 2008
003
Variables - ??, 2008 (Mike)
005
Improvements on property descriptions - ??, 2008 (All - split TBD)
006
Envelopes and Payloads (Steve) - Apr 30, 2008
007
(from draft 32) valueCalc (Mike) - ??, 2008   mostly
complete
008
(from draft 32) Property precedence for writing (Steve) - under review
009
(from draft 32) Variable markup (Steve) - Mar 31, 2008   proposal needs writing up
010
(from draft 32) Assertions, discriminators and choice, including discussion of timing option (Suman) - Mar 31, 2008 * in progress *
011
(from draft 32) How speculative parsing works (combining choice and variable-occurence - currently these are separate) ??, 2008 (IBM)  in progress
012
(from draft 32) Reordering the properties discussion: move representation earlier, improve flow of topics ??, 2008 (Alan) * not started *
025
Augmented infoset and unparsing (Alan)   added but needs work

complete - specification updated



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


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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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