[DFDL-WG] Fw: DFDL Discriminator - Question from Ruth

[Stephanie Fetzer]

All:

On the DFDL WG call  17NOV2010 my concern was that this rule was added 
'recently' but on closer review I see that it was just changed a bit 
("discriminators" changed to "dfdl:discriminators").  Ruth, Alan and I are 
all  in agreement  that this rule is a throwback to an earlier 
discrimination schema and needs to be removed.

The proposal is to remove the following from the spec:
In section 7.4 : "There can be at most one dfdl:discriminator  within a 
sequence group. It is a schema definition error if there is more than one 
dfdl:discriminator  annotation that applies to a single sequence group

I'm sending this email out with two purposes:
    1. Does anyone disagree and believe that this rules is still relevant?
    2. Is this change critical enough to amend the final spec or publish 
some form of errata to the specification? And if so, what is our next 
step?

Regards,

Stephanie Fetzer
WebSphere Transformation Extender (WTX)
Industry Packs - Architect

----- Forwarded by Stephanie Fetzer/Charlotte/IBM on 11/18/2010 07:54 AM 
-----

From:
Alan Powell/UK/IBM at IBMGB
To:
Stephanie Fetzer/Charlotte/IBM at IBMUS
Cc:
Ruth Wiegand/Boca Raton/IBM at IBMUS, Steve Hanson/UK/IBM at IBMGB
Date:
11/17/2010 05:55 AM
Subject:
Re: DFDL Discriminator - Question from Ruth


Stephanie

I think you are correct. That statement is probably left over from when 
the discriminator confirmed the existence of a parent.

 
Regards

 
Alan Powell
 
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
-------------------------------------------------------------------------------------------------------------------------------------------
IBM
MP211, Hursley Park
Hursley, SO21 2JN
United Kingdom
Phone: +44-1962-815073
e-mail: alan_powell at uk.ibm.com




From:   Stephanie Fetzer/Charlotte/IBM at IBMUS
To:     Steve Hanson/UK/IBM at IBMGB, Alan Powell/UK/IBM at IBMGB
Cc:     Ruth Wiegand/Boca Raton/IBM at IBMUS
Date:   16/11/2010 20:42
Subject:        DFDL Discriminator - Question from Ruth


Steve/Alan:

Was just talking with Ruth about the discriminators and I think we've got 
something in the spec that we may need to remove in this area.  Let me 
talk this out here first to see if perhaps I've remembered something 
incorrectly.

In section 7.4  we have: "There can be at most one dfdl:discriminator 
within a sequence group. It is a schema definition error if there is more 
than one dfdl:discriminator  annotation that applies to a single sequence 
group"

This makes perfect sense in WTX.  In WTX an identifier is placed on a 
component of a group. Then the identifier is proven to exist the parent 
exists.  Allowing only one per the sequence is necessary in this scheme. 
In DFDL we place the discriminator on the component being discriminated. 
So we have a rule that points to ones children such as ..if present child2 
then I exist.

I can not see how the 'one per sequence' gets us anything in CT in most 
cases.  We can't mean that only one of the parents in a sequence can 
contain a discriminator.  In EDI each segment in a loop can have a 
discriminator.  As we are using a rule at the parent it would be difficult 
(and not very useful) to restrict the rule to referencing only one child.  
So I'm confused - and I've confused Ruth.

Can we take five minutes from the WG call to straighten me back out again 
please?

Regards,

Stephanie Fetzer
WebSphere Transformation Extender (WTX)
Industry Packs - Architect


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.ogf.org/pipermail/dfdl-wg/attachments/20101118/a846ed93/attachment.html