They were added at the same time as dfdl:checkRangeInclusive() anbd dfdl:checkRangeExclusive() - https://redmine.ogf.org/projects/dfdl-wg/issues/314.

I know that the functions were intended to replace DFDL4S custom operators 'in' and 'inrange' which were used in assert expressions (see attached schemas).

I don't recall what the intersect & except operators use cases were though. I think you need to find the original action in the minutes.

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
Note: I work Tuesday to Friday

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: DFDL-WG <dfdl-wg@ogf.org>
Date: 03/08/2020 15:49
Subject: [EXTERNAL] [DFDL-WG] clarification: DFDL behavior of intersect, except operators
Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org>

Some time back there was an erratum to add intersect and except operators from XPath 2.0 to DFDL. I believe these were in use by the DFDL4S flavor of Daffodil, and so were added to DFDL v1.0.

Are these operators restricted to accept or to produce 0 or 1 node only, or are they able to accept and produce lists of nodes that can then be counted with fn:count, for example?

I guess I have lost track of the use-cases for these. The XPath 2.0 definition of these operators is of course fully general, accepting multiple node sequences, and producing multiple-node sequences. That would mean the ultimate result of these operators could be a sequence of more than one node, and that means it would have to be an argument to fn:count, fn:exists, .... not sure what other functions. They could never be the direct result-producing part of an expression.

Can someone point me at the use case for these again?

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Owl Cyber Defense | www.owlcyberdefense.com
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