[DFDL-WG] Fw: String literal syntax for hexBinary ?? - dfdl:property semantic

[Steve Hanson]

Agreed to drop dfdl:property() from 1.0.

Regards

Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 23/05/2012 18:19 -----

From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     Steve Hanson/UK/IBM at IBMGB
Cc:     dfdl-wg at ogf.org, Tim Kimber/UK/IBM at IBMGB
Date:   19/04/2012 23:35
Subject:        Re: [DFDL-WG] String literal syntax for hexBinary ?? - 
dfdl:property semantic




...  But are we all happy that the result of dfdl:property when the 
property value is an expression, is the result of executing that 
expression? How complicated is that going to make implementations?

Well, what is the use case for dfdl:property() at all?  One example would 
be where there is a choice, and different record formats as the 
alternatives of the choice depending on the length or number of 
occurrences of some element. So a discriminator expression would refer to 
dfdl:property("length",...) for example. 

However, I do believe we could drop dfdl:property(....), and just say "use 
variables if you want this behavior". E.g., if I have dfdl:length="{....}" 
then as the schema author I can always introduce a variable myLen, set its 
value to that of the expression, change to dfdl:length="{ $myLen }" and 
where I would have used dfdl:property("length", path), instead just 
reference the variable as $myLen. I will have to define the variable, and 
use newVariableInstance so that the variable goes into and out of scope 
appropriately just like a property value does, but this isn't horribly 
complex.

...mikeb



 
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