[DFDL-WG] clarification: DFDL behavior of intersect, except operators

[Steve Hanson]

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 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:   03/08/2020 15:49
Subject:        [EXTERNAL] [DFDL-WG] clarification: DFDL behavior of 
intersect,      except operators
Sent by:        "dfdl-wg" <dfdl-wg-bounces at 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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