If you parse and then serialize, are you bothered whether the { } are
preserved from input to output?
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: "Garriss Jr., James P."
I suggested the use of an escape scheme to handle this
Yes, you did. :-) You have correctly perceived the original intentions of these initiators/discriminators; however, in practice, the escape characters never appear, so they are genuinely superfluous, thus I don’t think the escape scheme approach is best.
The 'sequence' is more flexible as it gives you the possibility of hiding the brackets from the infoset using dfdl:hiddenGroupRef.
This is helpful, and I’ll try it this way.
Thank you!
From: Steve Hanson [mailto:smh@uk.ibm.com]
Sent: Monday, March 11, 2013 5:42 AM
To: Cranford, Jonathan W.
Cc: dfdl-wg@ogf.org; dfdl-wg-bounces@ogf.org; Garriss Jr., James P.
Subject: Re: [DFDL-WG] Optional Initiator and Terminator?
In an earlier email exchange on this subject, I suggested the use of an
escape scheme to handle this, assuming that the { } are either both absent
or both present, using properties escapeKind 'escapeBlock',
escapeBlockStart '{', escapeBlockEnd '}'. The disadvantage of this
approach is when serializing - you need to set property
generateEscapeBlock to 'always' or 'whenNeeded' - there is no setting for
'remember what it was when parsed'. That may or may not be a requirement
here.
If an escape scheme is not appropriate, then whether the 'choice' or
'sequence with optionality' approach is best is really up to you. It all
depends on how you want to manipulate the infoset subsequently. The
'sequence' is more flexible as it gives you the possibility of hiding the
brackets from the infoset using dfdl:hiddenGroupRef.
To Jonathan's point, if the { } are either both absent or both present.
you can place a dfdl:assert on the sequence which throws an error if the
brackets are unbalanced.
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: "Cranford, Jonathan W."