[DFDL-WG] Action 242 - valueLength and contentLength function wording

Mon Mar 24 10:53:24 EDT 2014

Note errata 3.9, my bolding:

"3.9. Section 12.3.5, 7.3.1, 7.3.2.  The spec originally allows lengthKind 
‘pattern’ to be used when the representation of the current element, or of 
a child element, is binary, but imposes restrictions on the encoding that 
can be in force. 

Clarify that the encoding property must be defined for the element (else 
schema definition error), and that a decoding processing error is possible 
if the match of the regex encounters data that does not decode in that 
encoding, dependent on the setting of encodingErrorPolicy. Remove section 
12.3.5.1.

Same clarifications needed for testKind ”pattern” property for asserts and 
discriminators.

For consistency, the restriction that a complex element of specified 
length and lengthUnits ‘characters’ must have children that are all text 
and that have the same encoding as the complex element, is dropped."

That's the restriction that I was referring to in my comment below.  I can 
see why it was dropped - basically the parser now just tries to decode n 
characters using the complex element's encoding (and encodingErrorPolicy). 
We could apply the same principle for dfdl:valueLength & 
dfdl:contentLength - you build the stream from the bottom up, and then 
decode it using the complex element's encoding (and encodingErrorPolicy ?) 
to get the length in characters. 

Note that's how unparsing for lengthKind 'prefixed' with lengthUnits 
'characters' would work as well  - the spec just says "For a complex 
element, the length is that of the ComplexContent region" which is not 
sufficient (12.3.4). Similar deal for lengthKind 'explicit' - in order to 
know the size in chars of ElementUnused the unparser needs to know the 
size in chars of the data first (12.3.7.3).

(Of course, for a fixed width encoding, you don't need to decode, you can 
just do the maths, but for the general case you need to decode. Also just 
doing the maths does not take encodingErrorPolicy into account).

Regards

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

From:   Steve Hanson/UK/IBM
To:     Mike Beckerle <mbeckerle.dfdl at gmail.com>, 
Cc:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, dfdl-wg-bounces at ogf.org
Date:   24/03/2014 12:55
Subject:        Re: [DFDL-WG] Action 242 - valueLength and contentLength 
function        wording

Mike

23.5.3.1. Value length is only a function of the dfdl:encoding property if 
the element has a text representation. Not sure this needs to be 
(re)stated here.

23.5.3.1. "The value length is computed from the DFDL infoset value, 
ignoring the dfdl:length or dfdl:textOutputMinLength property. Other DFDL 
properties which affect the length of a text or binary representation are 
respected, it is only an explicit length which is ignored." Last sentence 
is too imprecise - should be phrased in terms of the grammar. 

23.5.3.1. "If the second argument is 'characters' then the element must 
have text representation and it is a schema definition error otherwise". 
Yes but only for a simple type, so should be qualified.

23.5.3.1. "If the second argument, giving the length units, is 
'characters', then recursively, this complex type element must have text 
representation throughout all its contained elements and framing, all of 
which must also use a uniform character set encoding."  I can't see that 
restriction elsewhere in the spec when it talks about length of 
ComplexContent and lengthUnits 'characters' - I was expecting it to be in 
section 12.3.4 or 12.3.7.3 which face the same issue - but it isn't. Did 
we decide not to have this restriction? Without such a restriction, how 
does the unparser come up with a meaningful length (unless it re-parses)? 
(Tim - what does IBM DFDL do here?)  What about delimiters and padding of 
children that use %#r entities? 

23.5.3.2. The points in 23.5.3.1 about escape characters, length as a 
function of encoding, and bottom up for complex elements, apply equally to 
23.5.3.2.  It might be easier just to say in 23.5.3.2 that 
dfdl:contentLength for complex elements is same as dfdl:valueLength, and 
for simple elements differs only by the additional inclusion of 
LeftPadding and RightPadOrFill regions.

Also noted in passing:

Specified length - An item has specified length when dfdl:lengthKind is 
"implicit", "explicit", or "prefixed". 

should be 

Specified length - An element has specified length when dfdl:lengthKind is 
"implicit" (simple type only), "explicit", or "prefixed".  

Regards

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

From:   Mike Beckerle <mbeckerle.dfdl at gmail.com>
To:     "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>, 
Date:   20/03/2014 17:21
Subject:        [DFDL-WG] Action 242 - valueLength and contentLength 
function        wording
Sent by:        dfdl-wg-bounces at ogf.org

See attached doc which is proposed revisions to section 23.5.3

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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