Open Grid Forum: Data Format Description Language Working Group Weekly Working Group Conference Call 16:00 GMT, 9 Apr 2008 Attendees Mike Beckerle (Oco) Steve Hanson (IBM) Ian Parkinson (IBM) 1. OGF 23 and Face-to-Face meetings As DFDL was represented at OGF 22, we will skip OGF 23 (to be held in Barcelona). OGF 24 will be held in Singapore in September. Previous meetings have not attracted much interested in DFDL - Mike suggested that interest will pick up as we complete the specification and have implementations under way. DFDL was originally initiated by the OGF's Database Access and Integration Services project (DAIS), and Steve wondered whether this project still has a requirement and interest in DFDL. Mike has the opportunity to visit IBM Hursley, in the UK, to focus on progressing the specification in collaboration with the IBM working group members. This is tentatively scheduled for Monday June 2nd - Thursday June 4th. 2. Decimal supplement Discussion on the DFDL-WG mailing list raised a question: should TextNumberFormat, BinaryNumberFormat and FloatNumberFormat be left as separate properties, or combined into a single property with a greater selection of possible values? The meeting agreed that it is better to keep these as separate properties. The meeting reviewed the current distinction between binary coded decimal (BCD) and packed decimal, and agreed that the BCD format is never signed, while the packed decimal format always has a sign nibble. The "unpacked decimal" format, discussed on the mailing list, will remain unsupported for DFDL v1.0, but could be added later. Mike asked whether we should consider renaming the "decimalVirtualPoint" property to reflect the use of commas in many locales, perhaps "decimalVirtualSeparator" - the consensus was that this is unnecessary. 3. Regular Expressions A full review of the regular expressions proposal will wait until Alan can be present on a working group call. The proposal states that it represents a subset of XML schema's regular expression lanaguage, and it may be useful to identify features which are omitted. It may be useful, in a regular expression, to be able to use DFDL entity references to provide for byte sequences that are not subject to codepage conversion. Although Steve felt this not to be a requirement, Mike thought it difficult to justify such an omission. 4. Calculated Values Mike's document covering the use of inputValueCalc and outputValueCalc has undergone some revisions following discussion on the mailing list. The current (v3) draft contains a small error in the title of section 1.2. In cases where an element is not hidden, but has an outputValueCalc, it is currently not clear whether the outputValueCalc result takes precedence over any value present in the InfoSet. After some discussion, the group agreed that if such an element is present in the InfoSet, it must have the same value as the result of the calculation. An unparser should check this and fail the unparse if there is a mismatch. 5. Forward References The nilIndicatorPath, occursPath and lengthPath introduce a form of forward referencing, which had previously been outlawed by DFDL. This can make it difficult for a DFDL parser/unparser to implement streaming efficiently. Mike observed that there are likely to be a number of data formats which require a limited amount of forward referencing, such as record-based formats which involve a certain amount of "random access" in an individual record. He suggested that the restriction on forward references be lifted, with the caveat that mis-use of this feature can effectively prohobit streaming. This can further be discussed when Alan is available, as it affects the DFDL expression language. Meeting closed, 16:50 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