[DFDL-WG] Fw: UnorderedInitiated

[Steve Hanson]

It has been raised that the dfdl:unorderedInitiated property is redundant, 
because we have speculative parsing, and because the DFDL parser can 
optimise by analysis without being explicitly told. This is true but 
saying that all children of a  sequence have an initiator is also a way 
for the modeler to ensure that his model is correct and that all children 
are correctly specified.  I propose that we decide whether to:

a) Drop the property

b) Rename the property dfdl:initiated and have it apply to any sequence, 
ordered or unordered

There's also a question in the spec that we should resolve.

(TBD: do we allow sequences with initiators to be children of an unordered 
sequence, or do we require the children of an unordered sequence to be 
elements? Conservative would be to require elements.)
To which Mike had commented:

Suggest sequences where children have initiators cannot be directly 
nested. You must use an element in this case. I would prefer that children 
of an unordered sequence are required to be elements in general for v1.0.
I'd like to close on this as well. 

Let's discuss on today's call.

Regards

Steve Hanson
Programming Model Architect
WebSphere Message Brokers
Hursley, UK
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 29/04/2009 10:38 -----

Steve Hanson/UK/IBM
28/04/2009 15:41

To
Tim Kimber/UK/IBM
cc
Alan Powell/UK/IBM at IBMGB
Subject
Re: UnorderedInitiated





Here's the table from draft 0.33:


sequenceKind
separatorPolicy
Implications

unorderedInitiated
ignored (suppress behavior implied)
Initiators are used to identify which elements are present and which are 
missing.
All children must have dfdl:initiator strings that are distinct and not 
the empty string. (Schema definition error otherwise.)
nilValueInitiatorPolicy and defaultValueInitiatorPolicy must both be 
'required' (Schema definition error otherwise)

Setting unorderedInitiated forces extra checks to take place to ensure 
that an initiator would be present under all circumstances.  I think this 
provides a direct equivalent to TDS Tagged.

I'd prefer that speculative parsing was the sole mechanism used to resolve 
the child elements. In practice, most unordered sequences will have 
initiators on their children anyway.


There's also this comment in the spec:

(TBD: do we allow sequences with initiators to be children of an unordered 
sequence, or do we require the children of an unordered sequence to be 
elements? Conservative would be to require elements.)
To which Mike had commented:

Suggest sequences where children have initiators cannot be directly 
nested. You must use an element in this case. I would prefer that children 
of an unordered sequence are required to be elements in general for v1.0.
Which corresponds to schema's rule for xs:all and the MRM's rule for 
unorderedSet, so I'm happy with that.
 
Regards

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



Tim Kimber/UK/IBM
15/04/2009 23:26

To
Alan Powell/UK/IBM at IBMGB
cc
Steve Hanson/UK/IBM at IBMGB
Subject
Re: UnorderedInitiated





Hi Alan,

Understood. In that case, please can you add this to the list of 
unresolved issues in the specification. We should take pains not to 
include redundant properties in DFDL v1.0, because each property has a 
cost in terms of implementation, testing and documentation.

regards,

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




From:
Alan Powell/UK/IBM
To:
Tim Kimber/UK/IBM at IBMGB
Cc:
Steve Hanson/UK/IBM at IBMGB
Date:
15/04/2009 09:37
Subject:
Re: UnorderedInitiated


Tim

The problem with committees is that you can't just decide by yourself to 
drop something.

Alan Powell

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





From:
Tim Kimber/UK/IBM
To:
Alan Powell/UK/IBM at IBMGB
Cc:
Steve Hanson/UK/IBM at IBMGB, Dragan Besevic/Boca Raton/IBM at IBMUS, Sunil 
Dandamudi/Boca Raton/IBM at IBMUS, Lorenzito Jimenez/Boca Raton/IBM at IBMUS
Date:
14/04/2009 21:19
Subject:
Re: UnorderedInitiated


Alan,

Thanks for the clarification. If that is the only reason for the property 
then it should be removed in v0.34. The PIF generator can easily perform 
that kind of optimisation ( if necessary ).  This is not the only 
optimisation which the PIF generator might want to perform, and the 
specification does not supply extra properties for those other cases.

regards,

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





From:
Alan Powell/UK/IBM
To:
Tim Kimber/UK/IBM at IBMGB
Cc:
Steve Hanson/UK/IBM at IBMGB
Date:
14/04/2009 17:23
Subject:
Re: UnorderedInitiated


Tim

There is a history.

You are correct that speculative parsing should take care of it all. 
However originally unordered elements had to be initiated. When that was 
relaxed it was felt that it was worth giving the parser a chance to 
optimize to initiated case. Designed by committee.

Alan Powell

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





From:
Tim Kimber/UK/IBM
To:
Steve Hanson/UK/IBM at IBMGB, Alan Powell/UK/IBM at IBMGB
Date:
08/04/2009 22:54
Subject:
UnorderedInitiated


I can't see why this is required, but I'm probably missing something. 
Wouldn't the normal speculative parsing rules will make use of the 
initiator if it is present. Or does unorderedInitiated cause the initiator 
to behave as a discriminator? If so, I would prefer to leave that to the 
user. We don't do it for any other point of uncertainty ( there's no 
equivalent choiceInitiated setting ).

regards,

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












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