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 WebSphere ESB Development Mail Point 211, Hursley Park, Hursley, Winchester, SO21 2JN, UK Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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 WebSphere ESB Development Mail Point 211, Hursley Park, Hursley, Winchester, SO21 2JN, UK _____ Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
participants (2)
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Ian W Parkinson -
Mike Beckerle