[DFDL-WG] V3 of length/occurs simplification proposal
Steve Hanson
smh at uk.ibm.com
Thu Aug 30 07:28:56 CDT 2007
Property 'occursStopValueKind' has its origins in the analogous property
'nullValueKind'. They are both trying to solve the same kind of
out-of-band problem.
I would suspect that many users would be happier considering their array
as being terminated by an out-of-band stop value rather than by some odd
looking markup which combines a separator with a text value. You will
notice in your example that you have had to duplicate the occurs separator
in two properties, which immediately says to me that it's the wrong
approach.
Also, having literal and logical stop values gives us a bit more
flexibility. We may decide that stop values are considered data and give
rise to an API event. I think this needs more discussion, we need to take
into account the unparser side.
Regards, Steve
Steve Hanson
WebSphere Message Brokers
Hursley, UK
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848
"Simon Parker" <simon.parker at polarlake.com>
Sent by: dfdl-wg-bounces at ogf.org
30/08/2007 12:16
To
<dfdl-wg at ogf.org>
cc
Subject
Re: [DFDL-WG] V3 of length/occurs simplification proposal
Hmmm...
I wasn't around for 'occursStopValueKind', so excuse me if I miss the
point.
Here's a question and a tentative answer I was playing with recently:
What's the difference between stopValue and terminator?
'terminator' can be used to scan a stream of characters or bits without
parsing elements
'stopValue' can be used to scan a sequence of parsed elements. Its
datatype must be the same as the array element.
If I'm right, then Steve's example is invalid because "done" is not an
integer. To make it valid, either:
- the stopValue must be an 'int' such as -1, or
- the out-of-band value "done" or "|done" must be a terminator for an
enclosing construct as follows.
Change this:
<element name="x" type="int" maxOccurs="unbounded"
dfdl:occursSeparator="|" dfdl:occursKind="stopValue" dfdl:stopValue="done"
dfdl:occursStopValueKind="literal" dfdl:representation="text"/>
to this:
<sequence dfdl:lengthKind="delimited" dfdl:terminator="|done"
dfdl:applies="hereonly">
<element name="x" type="int" maxOccurs="unbounded"
dfdl:occursSeparator="|" dfdl:occursKind="endOfData"
dfdl:representation="text"/>
</sequence>
If I'm wrong, then what is the correct answer to the question?
---
If we change the name of the property 'stopValue', then I would find these
candidates consistent with similar concepts elsewhere:
occursTerminator
occursTerminatorValue
terminatorValue
Simon
From: dfdl-wg-bounces at ogf.org [mailto:dfdl-wg-bounces at ogf.org] On Behalf
Of Mike Beckerle
Sent: 29 August 2007 19:52
To: Steve Hanson
Cc: dfdl-wg at ogf.org; dfdl-wg-bounces at ogf.org
Subject: Re: [DFDL-WG] V3 of length/occurs simplification proposal
Seems like occursStopValueKind="literal" only applies to
representation="text".
With that caveat, I think I agree we need to be able to say
<element name="x" type="int" maxOccurs="unbounded"
dfdl:occursSeparator="|" dfdl:occursKind="stopValue" dfdl:stopValue="done"
dfdl:occursStopValueKind="literal" dfdl:representation="text"/>
Then this would be valid 3 occurences for element x.
2|3|4|done
I think we shoudl rename dfdl:stopValue to dfdl:occursStopValue for
consistency.
Mike Beckerle
STSM, Architect, Scalable Computing
IBM Software Group
Information Platform and Solutions
Westborough, MA 01581
direct: voice and FAX 508-599-7148
assistant: Pam Riordan
priordan at us.ibm.com
508-599-7046
Steve Hanson <smh at uk.ibm.com>
08/29/2007 01:32 PM
To
Mike Beckerle/Worcester/IBM at IBMUS
cc
dfdl-wg at ogf.org, dfdl-wg-bounces at ogf.org
Subject
Re: [DFDL-WG] V3 of length/occurs simplification proposal
Mike - looking at an old level of the spec, we had a occursStopValueKind
property, with enums 'logical', 'literal' and 'missing'. Analogous to
nullvalueKInd property. I'm sure we want to handle 'missing' differently
but the literal v logical distinction is required. How are we proposing to
cover this?
Regards, Steve
Steve Hanson
WebSphere Message Brokers
Hursley, UK
Internet: smh at uk.ibm.com
Phone (+44)/(0) 1962-815848
Mike Beckerle <beckerle at us.ibm.com>
Sent by: dfdl-wg-bounces at ogf.org
29/08/2007 16:29
To
dfdl-wg at ogf.org
cc
Subject
[DFDL-WG] V3 of length/occurs simplification proposal
Based on minutes from last week's meeting I've updated to v3 the proposal
for simplifying length/occurs properties.
Changes are marked with comments. --
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