Hi Mike

If I recall, choiceBranchKey was a single DFDL String Literal because the value to be matched against it is computed by a DFDL expression (from choiceDispatchKey), which can do things like lower casing strings or other manipulations. Are you seeing use cases where multiple keys per branch are making the expression too complex?

Regards

Steve Hanson

IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh@uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>
Date: 12/12/2016 19:48
Subject: [DFDL-WG] choiceBranchKey - suggest change to List of DFDL String Literals ?
Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org>

Our first experience with requiring and implementing choiceBranchKey in Daffodil and we're already dealing with the fact that many times the same branch has multiple different keys all of which indicate that it should be selected.

Right now, dfdl:choiceBranchKey is a DFDL String Literal, so values like dfdl:choiceBranchKey=" " (that's two spaces) are legal and will work. If it was to be a whitespace separated value, then those would have to use DFDL Entities to express the whitespace.

I know I have seen COBOL data where there were multiple tags that denote the same structure.

I am curious what others experience with choiceBranchKey is, and how this issue was handled.

I believe from prior emails that IBM has already implemented this in its DFDL implementation.

There is an erratum specifying that choiceBranchKey comparison is supposed to be case-sensitive (for performance reasons), but nothing heretofore about it using DFDL Entities to represent whitespace.

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com
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