[DFDL-WG] clarifications needed for %ES; and %WSP*; entities

[Steve Hanson]

Mike

Not true, the constraint that %ES; can never appear as part of any other 
token is already encapsulated in the grammar syntax for entities in 
6.3.1.2.

I'm not bothered about the WSP restrictions, it's clear what the effect of 
the token is. 

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:   06/09/2019 21:14
Subject:        [DFDL-WG] clarifications needed for %ES; and %WSP*; 
entities
Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org>



Currently, we have gaps in the spec. E.g., in discussion of 
dfdl:initiator, the spec says %ES; cannot appear alone in the list, but 
there is nothing prohibiting one from just using 
dfdl:initiator="%ES;%ES;" or dfdl:initiator="%ES: %ES;" to trivially work 
around this constraint, even though both of these definitions are 
nonsense. 

To avoid repeated discussion of this topic for each of initiator, 
terminator, and separator, these statements need to be made where ES and 
WSP* are defined, or in some other central location that discusses DFDL 
String Literals and whitespace separated lists thereof. 

%ES; can never appear as part of any other token. I.e., "%ES;A" is the 
same as just "A" regardless of what "A" is. So %ES; can only appear as a 
solitary token in a whitespace separated list of delimiter tokens or 
nilValue tokens. 

Furthermore, %ES; cannot be repeated in the list, since "%ES; %ES;" means 
the same thing as just "%ES;".

%WSP*; similarly cannot be repeated in the list meaningfully, so that 
should be prohibited as well.

(In fact repeating any token multiple times in the list can be 
prohibited.)

%WSP*; cannot be combined with %WSP+;, as the combination is equivalent to 
just %WSP+; by itself. Furthermore %WSP*;%WSP*; means the same as %WSP*; 
alone, so that should also be prohibited.

If we add these clarifications, then statements about how %ES; and %WSP*; 
and their specific constraints for dfdl:initiator and dfdl:terminator and 
dfdl:separator need not repeat these statements, and the constraints they 
express do not have obvious gaps. 

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | 
www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are 
subject to the OGF Intellectual Property Policy
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