[DFDL-WG] DFDL: Calculated Values section rewrite

Wed Apr 9 09:02:48 CDT 2008

Hmm. We're in this situation where DFDL is so rich with features that
anything those features don't handle will by definition be an obscure corner
case thereby hard to motivate.

I can change this example to use three single byte binary integers instead
of 6 packed decimal digits. This is certainly a feasible binary data format,
though it's nothing I've ever seen. It also makes the example orthogonal to
the decimal changes, so generally is more on point.

Attachment is new example plus the other improvements suggested.

  _____  

From: Steve Hanson [mailto:smh at uk.ibm.com] 
Sent: Wednesday, April 09, 2008 9:29 AM
To: mbeckerle.dfdl at gmail.com
Cc: dfdl-wg at ogf.org
Subject: Re: [DFDL-WG] DFDL: Calculated Values section rewrite

Comments from Ian and Steve: 

1) Is it a schema error if default/fixed attributes specified along with
dfdl:inputValueCalc and/or dfdl:outputValueCalc? 

2) 2D array. 
- dfdl:occurrences() is not in the expression language in draft 031. Is
something missing from the language, or should the XPath count() function be
used here? 
- $dfdl:occurrences - $ not needed 
- dfdl:outputValueCalc for 'ncols' - we think the else clause should be
'..\rows[1]\cols' 

3) PD date 
- As an example, it's perhaps not a good one as we have
decimalCalendarFormat as a property of a decimal number, which is intended
to do exactly this 
- As it stands, it will need updating to reflect latest decimal supplement 

Regards, Steve

Steve Hanson 
Programming Model Architect
WebSphere Message Brokers
Hursley, UK
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848 

"Mike Beckerle" <mbeckerle.dfdl at gmail.com> 
Sent by: dfdl-wg-bounces at ogf.org 

09/04/2008 02:44 

Please respond to
mbeckerle.dfdl at gmail.com

To

Alan Powell/UK/IBM at IBMGB 

cc

dfdl-wg at ogf.org, dfdl-wg-bounces at ogf.org 

Subject

Re: [DFDL-WG] DFDL: Calculated Values section rewrite

I've attached a revised calculated value properties doc which incorporates
suggestions from Alan, specifically, there's a new example, which is a 2-d
array with nrows, ncols fields stored before it. I think this motivates the
connection between outputValueCalc, and number of occurrences and occurs
calculations nicely. 

.mikeb 

  _____  

From: Alan Powell [mailto:alan_powell at uk.ibm.com] 
Sent: Thursday, March 27, 2008 2:02 PM
To: mbeckerle.dfdl at gmail.com
Cc: dfdl-wg at ogf.org; dfdl-wg-bounces at ogf.org
Subject: Re: [DFDL-WG] DFDL: Calculated Values section rewrite 

Mike 

A couple of comments on the using derived/representation nomenclature with
OutputValueCalc and a couple of minor corrections. 

However I thought the Length Prefix example a bit odd as I would have
expected a single HexBinary element rather than an array of bytes. 

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: 

<dfdl-wg at ogf.org> 

Date: 

26/03/2008 16:39 

Subject: 

[DFDL-WG] DFDL: Calculated Values section rewrite

  _____  

My deliverable for the next draft (32) was to revise the calculated values
section. 

I have rewritten it and the draft is attached. 

Of note: I have removed the troublesome "outputLengthCalc" property, as I no
longer see a critical need for it. One of the examples computes the number
of occurrences for a byte array, and I think that mechanism along with
alignment is sufficient to handle the troublesome cases I was considering
where size of padding had to be dynamically computed. 

The section now consists of a short table of definition, followed by
illustrative examples, however, I think this is fine. The semantics of
inputValueCalc and outputValueCalc aren't really that complex. They can be
described in a paragraph. It is the motivation for them that is complicated,
so I think examples in the spec, while sometimes considered problematic, are
OK in this case. 

[attachment "calculated-value-properties.doc" deleted by Alan Powell/UK/IBM]
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