Open Grid Forum: Data Format Description Language Working Group Working Group Conference Call 14:00 GMT, 16 Nov 2007 Attendees Mike Beckerle (IBM) Geoff Judd (IBM) Steve Hanson (IBM) Suman Kalia (IBM) Ian Parkinson (IBM) Alan Powell (IBM) 1. Introduction Mike called the meeting to discuss the revised Data Grammar portion of the DFDL specification, which he had previously circulated. This was discussed on the regular, weekly, conference call on 14th November, in Mike's absence. Mike will not be able to attend the next scheduled conference call. 2. Review of DFDL Data Grammar The meeting discussed the following points: As noted in the previous meeting, both the ComplexContent and ComplexElement productions include a "Prefix" element. Mike stated that this redundancy does exist in DFDL, but it sometimes necessary, e.g. for embedded groups. Steve suggested that, if this did need to be changed, we would do so with restrictions rather than a change to the productions. Suman suggested that the present grammar specification does not satisfactorily cover the case where the start of an array needs to be aligned, with individual array elements automatically being aligned. Mike suggested that this can be dealt with, in a DFDL schema, by encapsulating the array in an element or sequence.This would require the author to build additional encapsulation around the array, which Suman felt would be unnatural, and suggested it would be more natural to introduce a property to explicitly deal with this situation. Mike observed that the XML specification treats arrays as simply adjacent elements, so we should minimize the number of properties which affect an entire array rather than each individual element. Mike and Suman will collaborate on a concrete proposal to address this. Mike expressed discomfort with the use of "binary" and "opaque" to describe raw data, as these words ,ay be ambiguous. "opaque" in particular may refer to unparsed data, or to anyType elements. Suggested alternatives included "octets", "bits", "raw" and "blob". The SequenceContent production currently contains a "finalUnused" element. Mike wondered whether this would best be moved to the Sequence production. Suman felt that there would then be issues with prefixes and suffixes. The meeting saw no good reason to change this. Precedence order needs to be defined. Steve and Geoff will attempt to define a static order. Regarding the query raised at the previous meeting concerning initial prefix Separators and final postfix Separators, Mike confirmed that these had been removed following comments in a previous draft of the document. They had originally been intended to support certain properties which could be now be defined using other features of the grammar. Meeting closed 15:00 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