[DFDL-WG] questions/feedback on dfdl:assert

[Steve Hanson]

Jonathan - some replies below.

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:   09/07/2013 01:17
Subject:        [DFDL-WG] questions/feedback on dfdl:assert
Sent by:        dfdl-wg-bounces at ogf.org



DFDL WG,
 
Some questions and feedback on Section 7.3.1 Properties for dfdl:assert. I 
don’t think any of these are major issues.
 
> "Schema authors can insert xs:sequence constructs to control the timing 
of evaluation of statements more precisely."
 
An example here would illustrate and clarify the concept.  This same 
verbiage is used in other sections of the spec, but I would think that 
only a single example would be sufficient to demonstrate the technique.

SMH: This is the sort of thing that we envisaged being covered by one of 
our tutorials, but we will certainly consider adding an example. 
 
Under the “test” property:
> “The expression must have been evaluated by the time this element and it 
descendents have been processed.”
 
I’m lost in the grammar here.  Is that equivalent to “The expression must 
be evaluated before this element and its descendants are fully processed”? 
 (Changes highlighted).

Also, should the spec define what it means to “process” an element for 
this statement to have any weight?
 
SMH: The latest spec draft contains a new section 9.5 which prescribes the 
order in which the different DFDL annotations must be evaluated. I think 
that removes the need for this sentence in its current form and location.
 
> “It is a schema definition error if dfdl:test is the empty string and 
the value is
not specified and dfdl:testKind is 'expression' or not specified.”
 
Huh?  If the value of what isn’t specified? The value of the dfdl:assert 
annotation? 

SMH: Yes, the value of the dfdl:assert annotation. “It is a schema 
definition error if dfdl:testKind is 'expression' or not specified, and an 
expression is not supplied by either the value of the dfdl:assert element 
or the value of the dfdl:test attribute.”
 
Under the “testPattern” property:
> “It is a schema definition error if dfdl:testPattern is the empty string 
and the
value is not specified and dfdl:testKind is 'pattern'.”
 
Same comment here.  Should this be “… and the value of the dfdl:assert 
annotation is not specified…”?

SMH: “It is a schema definition error if dfdl:testKind is 'pattern', and a 
pattern is not supplied by either the value of the dfdl:assert element or 
the value of the dfdl:testPattern attribute.”
 
> “In order for a testPattern to be used, the data subject to the pattern 
must be
scannable using a DFDL regular expression otherwise the results are not
predictable.”
 
What does it mean for data to be “scannable”?  Does this mean that the 
representation has to be text, since it's the physical representation of 
the data that is compared to the regular expression? 

SMH: Scannable is defined in section 12.3.5.1. It would make better sense 
for it to be defined in section 3 (Glossary) as it is used for both assert 
terstKind 'pattern' and lengthKind 'pattern'.
 
Very respectfully,
 
--
Jonathan W. Cranford 
Senior Information Systems Engineer
The MITRE Corporation (http://www.mitre.org)
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