I believe we also decided to eliminate control
over stop value kinds i.e., to eliminate the logical vs. literal distinction
and just have logical as the behavior. This eliminates the kind control
property for stop values.
From:
dfdl-wg-bounces@ogf.org [mailto:dfdl-wg-bounces@ogf.org] On Behalf Of Ian W Parkinson
Sent: Tuesday, May 06, 2008 12:58
PM
To: dfdl-wg@ogf.org
Subject: [DFDL-WG] DFDL: Minutes
from OGF WG call, 30 Apr 2008
Hi all,
I've
just noticed - I didn't distribute the minutes from last week's WG call.
Apologies for the delay.
Cheers,
Ian
Open Grid Forum: Data Format Description Language Working Group
Weekly Working Group Conference Call
16:00 GMT, 30 Apr 2008
Attendees
Mike Beckerle (Oco)
Steve Hanson (IBM)
Ian Parkinson (IBM)
Alan
Powell (IBM)
1. F2F meeting at IBM Hursley
Mike
has confirmed that he will travel to IBM Hursley to further design discussions
with the IBM team, later in May.
2. Review of specification line items
The
meeting began a review of the outstanding work required for specification draft
32, but this was not completed during the meeting as a number of technical discussions
were triggered.
- valueCalc
Mike has provided material to Alan. No further work is anticipated on this
item.
- nulls/defaults/optionals
There has been some discussion on nilIndicatorPath and forward references,
and this discussion needs to continue. The rest of this section is now
complete.
- UML
description of schema components
complete
- Property
Precedence This item is currently
marked complete; however it has sparked some discussion. On unparse, if
the infoset contains less than the required number of occurances of some
field, then the unparser may be expected to output sufficient instances of
the default value. We need to craft a policy to determine exactly how this
achieved; for example, do we use the xsd:minOccurs value or do we try to
match the result of the dfdl:occurs expression? Mike proposed that if an
occurs expression is present, it must evaluate to a valid number of
occurances. Steve suggested that we disambiguate dfdl:occurs from
xsd:minOccurs and xsd:maxOccurs by renaming the property dfdl:occursPath -
however, this property can be an expression involving calculations, not
just a simple path. A number of simplifications have been proposed, and
these require further discussion.
Alan noted that an XPath expression has no way to
access a field's default value, and suggested introducing a function to handle
this. Also, we may need to define count() such that it returns the number of
instances of an element after any necessary padding and introduce a different
way to obtain the number of instances found in the infoset.
Stop
values and terminators are not considered part of the logical data.
Steve
will update the diagram.
- Variable
Markup Steve had previously
proposed a scheme whereby properties, such as iniitator or terminator,
could be described by another DFDL element or type definition. We could
use a similar mechanism to handle strings with embedded complex
structures. This subject will be tackled during the F2F.
- Regular
Expressions for Lengths The meeting agreed to
adopt the regular expression subset previously distributed by Alan.
Regular expressions are ignored for unparsing, and are only used to
determine the length of an element during parsing. Considering repeating
elements, Steve contrasted the behaviour of regular expressions in DFDL
(where the regular expression matches just a single instance) with that in
IBM's MRM technology (where a regular expression matches the entire
array), and the meeting discussed whether a regular expressions should
include any necessary terminators.
Meeting closed, 17:10 GMT
Ian Parkinson
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