[DFDL-WG] action 224: add section for implementation defined limits

[Steve Hanson]

Jonathan

Thanks for citing that example. I have added a summary to the minutes of 
yesterday's WG call. 

Please go ahead and trawl the document for implementation 
defined/dependent things.

Please also raise a public comment to track, at 
http://redmine.ogf.org/projects/editor-pubcom/boards/15.

Regards

Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh at uk.ibm.com
tel:+44-1962-815848



From:   "Cranford, Jonathan W." <jcranford at mitre.org>
To:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, 
Date:   17/09/2013 16:11
Subject:        [DFDL-WG] action 224: add section for implementation 
defined limits
Sent by:        dfdl-wg-bounces at ogf.org



All,
 
Action item 224 was raised two weeks ago during the WG call. 
 
224 Add section for implementation defined limits (All)
3/9: Several places in the spec cite this, should be grouped. Currently 
partially listed in section
2.6.
Also note distinction between 'implementation defined' and 'implementation 
dependent'. Check
spec for correct usage.
Resolve during public comment.
 
The action item was created based on a comment I made during the call, so 
I thought it’d be good to provide an example of the distinction I was 
trying to make.
 
The W3C XProc specification does a great job of differentiating between 
implementation-defined and implementation-dependent features, with a 
convenient list of each in the appendix.
 
Appendix A (http://www.w3.org/TR/xproc/#conformance) contains the 
following text.
Conformant processors must implement all of the features described in this 
specification except those that are explicitly identified as optional.
Some aspects of processor behavior are not completely specified; those 
features are either implementation-dependent or implementation-defined.
[Definition: An implementation-dependent feature is one where the 
implementation has discretion in how it is performed. Implementations are 
not required to document or explain how implementation-dependent features 
are performed.]
[Definition: An implementation-defined feature is one where the 
implementation has discretion in how it is performed. Conformant 
implementations must document how implementation-defined features are 
performed.]
 
Section A.1 then lists all the implementation-defined features, and 
section A.2 lists all the implementation-dependent features.
 
I think the XProc spec provides a great example to follow on two counts. 
First, it formally distinguishes between implementation-defined and 
implementation-dependent features.  The choice of terms isn’t nearly as 
important as the distinction itself, of course:  implementations must 
document how certain features are implemented.  In the DFDL realm, section 
2.6 lists some implementation limits which always constitute schema 
definition errors; surely these are the types of details that must be 
documented by any DFDL implementation.  Using terminology such as 
“implementation-defined” and “implementation-dependent” would flag these 
types of documentation requirements for implementations within the 
specification.
 
Second, all the implementation-defined and implementation-dependent 
features are listed in one place in the specification.  I think doing the 
same in the DFDL spec would provide a great resource for DFDL 
implementers.
 
Comments?  If everyone agrees, I don’t mind taking the action to search 
through the document looking for candidates for inclusion in such a list.
 
Sincerely,
 
--
Jonathan W. Cranford 
Senior Information Systems Engineer
The MITRE Corporation (http://www.mitre.org)
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