[DFDL-WG] clarification needed: choice with direct dispatch is/is-not a PoU

[Steve Hanson]

I don't agree, because unlike an array with a fixed number of occurrences, 
it is a processing error if the value of the expression does not match any 
of the dfdl:choiceBranchKey property values for any of the branches. Which 
currently causes backtracking because there is a PoU. 

I consider direct dispatch as more like the use of dfdl:initiatedContent 
when resolving a choice.

This is not a behaviour that can be changed in DFDL 1.0, it would affect 
too many existing schemas. For example, IBM's DFDL schemas for SWIFT make 
heavy use of direct dispatch.

Regards
 
Steve Hanson
IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh at uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday 



From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     DFDL-WG <dfdl-wg at ogf.org>
Date:   13/07/2020 14:50
Subject:        [EXTERNAL] [DFDL-WG] clarification needed: choice with 
direct dispatch is/is-not a PoU
Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org>




Just like an array with a computed number of occurrences, I believe a 
choice with direct dispatch should have no PoU.

But the spec has this phrase "An xs:choice is always a point of 
uncertainty. It is resolved sequentially, or by direct dispatch."

Which suggests there is a role for asserts/discriminators in resolving a 
choice by direct dispatch even though there shouldn't be.

I think we should clarify this to "An xs:choice either is a point of 
uncertainty, or uses direct dispatch."

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | 
www.owlcyberdefense.com
Please note: Contributions to the DFDL Workgroup's email discussions are 
subject to the OGF Intellectual Property Policy
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