1. Current Actions

2 Semantics of newVariableInstance and setVariable

what should a DFDL processor ( parser or serializer ) do when it cannot evaluate the expression in a newVariableInstance or setVariable annotation?

Moving the setting of variable values into the END_ELEMENT state just creates other problems A new instance must be available to other expressions on the same component, and to the children of a group/element. So it cannot be left until the end of the element.
On the other hand, there are clearly some types of setVariable / newVariableInstance annotations which *cannot* be evaluated until the END_ELEMENT state.

For the parser, it might be OK to
- evaluate the expression when the component ( element or group ) is started
- if it cannot be evaluated, add it to a list of annotations that must be processed at the end of the component
- if in the mean time any other expressions attempt to access the variable that was being set/created then throw a processing error ( because the result will be undefined ). This will probably require the variable/instance to be placed into a 'not available' state until its expression is resolvable

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
...
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 progressing
31/03: work is progressing
14/04: And XML test case format has been defined and is being tested.
21/04. Schema for TDML defined. Need to define how this and the test cases will be made public
05/05: Work still progressing
12/05: Work still progressing
02/06: Work still progressing on technical and legal considerations
...
21/07: work continues
04/08: work continues

085
ALL: publicize Public comments phase to ensure a good review..
14/04: see minutes
21/04: Press release, OMG and other standards bodies.
05/05: Alan and Steve H have contacted other standards bodies. Will ask them to add comments on spec
15/05: still no public comments
02/06: No public comments
16/06: Public comments period has ended with no external comments. Alan had posted changes made in draft 041. Steve suggested send a note to the WG highlighting these changes. Steve also suggested requesting an extension as other IBM groups may review. We discussed whether this was necessary as changes will need to be made during the implementation phase anyway. Alan to ask OGF what the process is for changes post public comment.
23/06: Still no comments. Alan will contact OGF to understand the rest of the process.
30/06: Alan has emailed Joel asking what the process is now public comment period is over andcan we update the published version with WG updates. No response yet.
07/07: No response. Alan will chase up
14/07: No response from Joel. Sent email to Greg Newby by no response.
21/07: Still no response.
04/08: Joel has responded that it is up to the WG to decide if the changes are significant enough to need additional review. Alan to contact David Martin and Erwin Laure for guidance if we split the specification.

099
Splitting the specification in simpler sections.
07/07: Steve sent a proposal but not discussed. Alan will arrange a separate call.
14/07:Discussed Steve's proposal and Suman's and Alan's comments.
Need to add choice, validation, facets.
Also how does an implementation declare which subsets it supports. Suggested levels and/or profiles. Steve highlighted a problem when a DFDL schema from an implementation of just the core functions was moved to a full DFDL implementation what should happen about the missing properties. Does the full implementation need to be aware of subsets of functions? Should it raise a schema definition error for use of a function not in the subset.
21/07: no progress
04/08: Steve had updated proposed groups of function. (Subset_proposal_v2.ppt). We discussed whether its is better to have discrete sets of functions or expanding levels of function.
Purpose of subsetting is:
1. Allow simpler implementations. (main purpose)
2. Simplify tooling
3. Simplify specification.
Steve to contact previous members of WG to check if we have the correct subsets.

101
Semantics of 'fixed'
21/07: Discussed whether not matching the 'fixed' value should be a validation error or processing error. Decided that for consistency it should be a validation error.
It would be useful however to avoid having to duplication of facet information in an assert which could become unwieldy for, say, a large enumeration.
Suggestions
- a parser option that 'converted all validation errors to porcessing errors'
- a dfdl expression function that 'applied all facets' or 'applied specific facet' to a particular element.
Stephanie will produce some examples of how this could be used..
04/08: Stephanie had produced examples but they were not discussed due to lack of time

104
Expressions
Discuss error behaviour when evaluating an expression in various contexts
- All properties:
wrong type returned : schema definition error
exception when evaluating expression : schema definition error
referenced variables/paths not available : schema definition error
- Properties which allow a forward reference
referenced variables/paths not available : no error. DFDL processor continues processing until the expression result is available, then acts on the result.
21/07: Steve stated the current definition that returning the incorrect type was a schema definition error and everything else was a processing error.
04/08: Not discussed

107
teston/testoff dfdl expression functions.
Are these functions still needed. They were introduced to allow individual bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that use existence flags to see if they are still required.
04/08: Not discussed

108
dfdl:hidden
There has been some discussion on whether the 'hidden' global group should be indicated in some way.
04/08: A lively discussion. The specification is works as currently defined so whether changes need to be made to make tooling easier. There shouldn't be 'conventions' in particular tooling as they must be able to properly deal with schema from other tools that would not obey those conventions. Steve stated that it is often dangerous to hide too much from users when they can see they underlying schema. To be continued.

109
dfdl:discriminator : the 'message' attribute
>From Tim:
I remembered the reason why I thought this was a good idea.
Consider the situation where someone is generating their DFDL schema from meta-data. The model is large, and consists of many references to global structures. Each global structure ( e.g. an HL7 segment ) is identified in a particular way. Sometimes the segment is required, sometimes it is not. Sometimes it occurs as a child of a choice group, and sometimes not. Regardless, it is highly likely that the segment will be identified in the same way wherever it occurs. A natural decision for the modeler would be to create a dfdl:discriminator on all references to the segement, even if the ref is not under a point of uncertainty. It's harmless, and it carries no performance penalty. If we disallow the "message" attribute, it will force the modeler to put in extra logic to work out whether the ref is under a POI, and generate an assert/discriminator as appropriate.

I'd be interested to know what Steph thinks about this - I think I've heard her say that she sometimes uses discriminators where an assert would have done the job, just to maintain consistency throughout the model.
04/08: not discussed.

Regards

Alan Powell

Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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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 ... 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 progressing 31/03: work is progressing 14/04: And XML test case format has been defined and is being tested. 21/04. Schema for TDML defined. Need to define how this and the test cases will be made public 05/05: Work still progressing 12/05: Work still progressing 02/06: Work still progressing on technical and legal considerations ... 21/07: work continues 04/08: work continues
085	ALL: publicize Public comments phase to ensure a good review.. 14/04: see minutes 21/04: Press release, OMG and other standards bodies. 05/05: Alan and Steve H have contacted other standards bodies. Will ask them to add comments on spec 15/05: still no public comments 02/06: No public comments 16/06: Public comments period has ended with no external comments. Alan had posted changes made in draft 041. Steve suggested send a note to the WG highlighting these changes. Steve also suggested requesting an extension as other IBM groups may review. We discussed whether this was necessary as changes will need to be made during the implementation phase anyway. Alan to ask OGF what the process is for changes post public comment. 23/06: Still no comments. Alan will contact OGF to understand the rest of the process. 30/06: Alan has emailed Joel asking what the process is now public comment period is over andcan we update the published version with WG updates. No response yet. 07/07: No response. Alan will chase up 14/07: No response from Joel. Sent email to Greg Newby by no response. 21/07: Still no response. 04/08: Joel has responded that it is up to the WG to decide if the changes are significant enough to need additional review. Alan to contact David Martin and Erwin Laure for guidance if we split the specification.
099	Splitting the specification in simpler sections. 07/07: Steve sent a proposal but not discussed. Alan will arrange a separate call. 14/07:Discussed Steve's proposal and Suman's and Alan's comments. Need to add choice, validation, facets. Also how does an implementation declare which subsets it supports. Suggested levels and/or profiles. Steve highlighted a problem when a DFDL schema from an implementation of just the core functions was moved to a full DFDL implementation what should happen about the missing properties. Does the full implementation need to be aware of subsets of functions? Should it raise a schema definition error for use of a function not in the subset. 21/07: no progress 04/08: Steve had updated proposed groups of function. (Subset_proposal_v2.ppt). We discussed whether its is better to have discrete sets of functions or expanding levels of function. Purpose of subsetting is: 1. Allow simpler implementations. (main purpose) 2. Simplify tooling 3. Simplify specification. Steve to contact previous members of WG to check if we have the correct subsets.
101	Semantics of 'fixed' 21/07: Discussed whether not matching the 'fixed' value should be a validation error or processing error. Decided that for consistency it should be a validation error. It would be useful however to avoid having to duplication of facet information in an assert which could become unwieldy for, say, a large enumeration. Suggestions - a parser option that 'converted all validation errors to porcessing errors' - a dfdl expression function that 'applied all facets' or 'applied specific facet' to a particular element. Stephanie will produce some examples of how this could be used.. 04/08: Stephanie had produced examples but they were not discussed due to lack of time
104	Expressions Discuss error behaviour when evaluating an expression in various contexts - All properties: wrong type returned : schema definition error exception when evaluating expression : schema definition error referenced variables/paths not available : schema definition error - Properties which allow a forward reference referenced variables/paths not available : no error. DFDL processor continues processing until the expression result is available, then acts on the result. 21/07: Steve stated the current definition that returning the incorrect type was a schema definition error and everything else was a processing error. 04/08: Not discussed
107	teston/testoff dfdl expression functions. Are these functions still needed. They were introduced to allow individual bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that use existence flags to see if they are still required. 04/08: Not discussed
108	dfdl:hidden There has been some discussion on whether the 'hidden' global group should be indicated in some way. 04/08: A lively discussion. The specification is works as currently defined so whether changes need to be made to make tooling easier. There shouldn't be 'conventions' in particular tooling as they must be able to properly deal with schema from other tools that would not obey those conventions. Steve stated that it is often dangerous to hide too much from users when they can see they underlying schema. To be continued.
109	dfdl:discriminator : the 'message' attribute >From Tim: I remembered the reason why I thought this was a good idea. Consider the situation where someone is generating their DFDL schema from meta-data. The model is large, and consists of many references to global structures. Each global structure ( e.g. an HL7 segment ) is identified in a particular way. Sometimes the segment is required, sometimes it is not. Sometimes it occurs as a child of a choice group, and sometimes not. Regardless, it is highly likely that the segment will be identified in the same way wherever it occurs. A natural decision for the modeler would be to create a dfdl:discriminator on all references to the segement, even if the ref is not under a point of uncertainty. It's harmless, and it carries no performance penalty. If we disallow the "message" attribute, it will force the modeler to put in extra logic to work out whether the ref is under a POI, and generate an assert/discriminator as appropriate. I'd be interested to know what Steph thinks about this - I think I've heard her say that she sometimes uses discriminators where an assert would have done the job, just to maintain consistency throughout the model. 04/08: not discussed.