[DFDL-WG] output value calc

Sun Jul 5 06:18:52 CDT 2009

Alan et al,

I have incorporated the feedback to the outputValueCalc document. Version
004 is attached.

I introduced new terminology. Specified length vs. Scanned length. A
specified length is prefix, implicit or explicit. And also endOfParent when
the parent recursively has specified length. The other cases are scanned
length. These may not be the best names for these concepts, but I wanted to
enumerate all the various lengthKind values that result in a potential for
padding/filling/truncation only once.

There is a new action item coming out of this work to specify bit-field
behavior. E.g., example of a vector of 14-bit fields stored back-to-back,
and how that interacts with byteOrder big or little endian.

(Alternatively, we could punt on lengthUnits="bits" entirely for DFDL v1.0,
and similarly alignmentUnits="bits". I don't like it, but it is a very
separable thing.)

...mike

On Wed, Jun 24, 2009 at 7:41 AM, Steve Hanson <smh at uk.ibm.com> wrote:

>
> Alan
>
> Just to be clear - the box use case actually covers three sub-cases.
>
> 1) lengthKind="explicit" and length is hard-coded
> 2) lengthKind="explicit" and length is carried earlier in the data
> 3) lengthKind="prefix"
>
> Regards
>
> Steve Hanson
> Programming Model Architect
> WebSphere Message Brokers
> Hursley, UK
> Internet: smh at uk.ibm.com
> Phone (+44)/(0) 1962-815848
>
>
>  *Alan Powell/UK/IBM at IBMGB*
> Sent by: dfdl-wg-bounces at ogf.org
>
> 24/06/2009 09:09
>   To
> Mike Beckerle <mbeckerle.dfdl at gmail.com>
>  cc
> dfdl-wg at ogf.org
>  Subject
> Re: [DFDL-WG] output value calc
>
>
>
>
>
> Mike
>
> We originally decided that lengthUnit=characters wasn't allowed on sequence
> and choice because of complications with encodings etc. Then when we removed
> lengthKind from sequence and choice it moved up to the complex element.
> Remember that this is only to support the box use case and it seems
> unlikely you would specify the size of the box in characters.
>
> Alan Powell
>
> MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
> Notes Id: Alan Powell/UK/IBM     email: alan_powell at uk.ibm.com
> Tel: +44 (0)1962 815073                  Fax: +44 (0)1962 816898
>
>
>   From: Mike Beckerle <mbeckerle.dfdl at gmail.com>  To: Alan
> Powell/UK/IBM at IBMGB  Cc: dfdl-wg at ogf.org  Date: 23/06/2009 19:07  Subject: Re:
> [DFDL-WG] output value calc
>
>  ------------------------------
>
>
>
>
> I've viewed your comments and will incorporate them and resubmit.
>
> One question is about complex types and text representation.
>
> You mentioned we don't allow lengthKind="characters" on complex types.
> Seems to me if representation="text" it is quite likely that everything is
> given in lengthUnits="characters".
>
> I'm not sure why not, though I have vague recollection of this restriction
> being discussed. Can you remind me?
>
> ...mike
>
> On Tue, Jun 23, 2009 at 7:06 AM, Alan Powell <*alan_powell at uk.ibm.com*<alan_powell at uk.ibm.com>>
> wrote:
>
> Mike
>
> Comments from our review in attached doc
>
>
> Alan Powell
>
> MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
> Notes Id: Alan Powell/UK/IBM     email: *alan_powell at uk.ibm.com*<alan_powell at uk.ibm.com>
> Tel: +44 (0)1962 815073                  Fax: +44 (0)1962 816898
>
>   From: Mike Beckerle <*mbeckerle.dfdl at gmail.com*<mbeckerle.dfdl at gmail.com>
> >  To: *dfdl-wg at ogf.org* <dfdl-wg at ogf.org>  Date: 19/06/2009 04:13
> Subject: [DFDL-WG] output value calc
>
>
>  ------------------------------
>
>
>
>
>
> New draft of output value calc stuff. based on prior review (last week)
> which simplified and clarified things somewhat.
>
> Examples are a simple and a complex type, with the same context - fits in a
> box that is rounded up in size to next multiple of 4 bytes.
>
> There's some material in here also about bit strings and use of dfdl:length
> measured in bits. This was to cover truncation fully. It is not a
> comprehensive treatment of bit fields though.
>
> All mention of variables and/or parameters is gone.
>
> See what you think.
>
> ....mike
>
> Mike Beckerle | OGF DFDL WG Co-Chair | CTO | Oco, Inc.
> Tel:  781-810-2125  | 100 Fifth Ave., 4th Floor, Waltham MA 02451 | *
> **mbeckerle.dfdl at gmail.com* <mbeckerle.dfdl at gmail.com>*[attachment
> "outputValueCalc-and-variables-003.doc" deleted by Alan Powell/UK/IBM] *--
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