[DFDL-WG] Minutes for OGF DFDL Working Group Call, March 17-2010

Thu Mar 18 11:56:54 CDT 2010

Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, March 17-2010

Attendees
Suman Kalia (IBM) 
Steve Hanson (IBM) 
Alan Powell (IBM) 
Steve Marting (Progeny) 
Stephanie Fetzer (IBM)
Mike Beckerle (Oco)

Apologies
Tim Kimber(IBM) 

Steve H reported on the DFDL presentation at OGF 28
Overall OGF registered attendees thought to be around 250. 

Number at DFDL session: 7.  Apart from Erwin (Data AD), DFDL was new to 
everyone. 

Notes from session (from minutes taken by Erwin Laure based on questions 
asked): 
Validation on input and output? Means conforming to the schema defined 
(e.g. integer between 0 and 100). dfdl assert could be used for asserting 
correctness of the data. Further complex validation would be via an 
external step (eg, Schematron invocation). 
Using DFDL to model data structures generated by OO code, particularly use 
of inheritance? Could be a use case for allowing complex type inheritance 
in DFDL in the future. 
Data often comes with units, infoset would want to reflect this? Could be 
achieved using expressions, dfdl:inputValueCalc and dfdl:hidden to apply a 
scaling factor based on units. 
What's the efficiency of DFDL? Particularly, can tests be turned off for 
fast read/write? The spec defines the behavior of the parser but not how 
to implement it. For instance, validation is not mandatory. 
Open source reference implementation would be good to have. (Lots of 
nodding). 
Scientific floating point data compresses badly. Knowing data structure 
can allow a more intelligent compression. DFDL is not intending to do 
transformations but that could be done on top. 
Encryption/compression could also be a use case for multi-layers, or for 
additional functions in the expression language. 
Need to reach out to DAIS-WG and DR-WG for (public) comments and to see 
whether DFDL will be actively used by those groups. Open source 
implementation would obviously help here. 
Comment on the spec: Should be a proposed recommendation (GFD-P-R) not 
informational (GFD-I).

Draft 040 has been submitted to OGF and will be reviewed by the technical 
committee on March 30th. It is expected to go out for public comment in 
early April.

There needs to be some publicity to ensure that enough comments are made.
Mike suggested a press release from his company with IBM comment.  Action 
raised
May be able to get IBM representatives on other standards bodies such as 
ACCORD. OMG, to interest their members,
Should contact all the contributors to the WG to ask them to review.
Mike will update the information he sent in response to an RFI from OMG

1 Process for dealing with internal issues during Public comment phase.
The public comments process will be used to make updates

2. Nils and Defaults during unparsing 
The table 17 in section 13.16.2 was corrected in draft 40 but here are 
still some ambiguities, for example when nil is the default. 
Logical Value
nilValueInitiatorPolicy
Has default value specified
missingValueInitiatorPolicy
initiator region contains
content region contains
Nil 
(implies nillable)
prohibited
don't care 
don't care 
empty
representation of nil based on nilKind, nilValue, etc.
required
initiator string
"" (empty string) 
Note that this implies that the element type is xs:string
don't care
prohibited
empty
empty string
required
initiator string 
a non-nil non-empty-string value
don't care
don't care
initiator string
The representation of the logical value
Not supplied
don?t care
Yes 
(non-empty sting)
don't care
Initiator string 
The representation of the default value.
Yes 
(empty string)
prohibited
empty
empty
required
initiator string
empty

Alan will go update the table.

3 dfdl:choiceKind 

The main issues  are: 
a) The calculation of the length of the longest branch is not obvious. 
b) The length units to use - the dfdl:lengthUnits property does not exist 
on a choice 
c) The name could be better 

Proposal is therefore to retain the property but to: 
i) State the conditions that must apply to use this property, and enforce 
them in the validator => schema definition error otherwise 
ii) Decouple the choice from its parent by calculating the length of each 
branch based solely on the properties of the branches components, 
irrespective of any parent dfdl:lengthKind 

Alan document the problem. Name change agreed.

4 DFDL time functions 

fn:timezone-from-dateTime 
Returns the timezone from an xs:dateTime value.

fn:timezone-from-date 
Returns the timezone from an xs:date value.

fn:timezone-from-time 
Returns the timezone from an xs:time value.

Function
Meaning
fn:adjust-dateTime-to-timezone 
Adjusts an xs:dateTime value to a specific timezone, or to no timezone at 
all. 
fn:adjust-date-to-timezone 
Adjusts an xs:date value to a specific timezone, or to no timezone at all. 

fn:adjust-time-to-timezone 
Adjusts an xs:time value to a specific timezone, or to no timezone at all.

All return an xs:duration. Do we need these functions? 
As there is no known use case for these functions they will be dropped.

Meeting closed, 14:10

Next call  Wednesday 17 March January 2010  13:00 UK  (9:00 ET)
Call will be for one hour only
NOTE: East coast is 4 hours behind the UK for the next two weeks

Next action: 087
Actions raised at this meeting

No
Action 
085
ALL: publicize Public comments phase to ensure a good review..
086
AP: Nils and Defaults during unparsing - update table

Current Actions:
No
Action 
066
Investigate format for defining test cases
25/11:IBM to see if it is possible to publish its test case format.
04/12: no update
09/12: no update
16/12: reminded dent to project manager
23/12: SH will send another reminder.
06/01: Another reminder will be sent
13/01: no update
20/01: no update
27/01: no progress
29/01: no progress
03/02: IBM is still investigating
10/02: IBM is still investigating
17/02: IBM is willing in principle to publish the test case format and 
some of the test cases. May need some time to build a 'compliance suite'
24/03: No progress
03/03: Discussions have been taking place on the subset of tests that will 
be provided.
10/03: work is progressing
17/03: work is progressin
084
Check behaviour of dfdl:inputValueCalc and outputValueCalc.
085
ALL: publicize Public comments phase to ensure a good review..
086
AP: Nils and Defaults during unparsing - update table

Closed actions
No
Action 

Work items:
No
Item
target version
status
005
Improvements on property descriptions 

not started
012
Reordering the properties discussion: move representation earlier, improve 
flow of topics 

not started 
036
Update dfdl schema with change properties 
ongoing

042
Mapping of the DFDL infoset to XDM 
none
not required for V1 specification
070
Write DFDL primer 

071
Write test cases.

083
Implement RFC2116

097
Remove functions that returns duration

Regards

Alan Powell

Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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