Thanks for the explanation, Mike. This helpful principle is expressed on page 105: "a parser for any construct (simple or complex) consumes its own delimiters and only its own delimiters" Separators belong to the file, terminators belong to the record. The lenient record-per-line text file can be viewed in several ways, such as: file with prefix separators and optional terminator = [record, {newline, record}], [newline]; file with suffix separators and optional terminator = [{record, newline}, record], [newline]; file with terminated records last optional = {terminated record}, [record]; terminated record = record, newline; record = characters except newline; newline = CR, LF; Is there anything to choose between these interpretations? Perhaps it's not our business to worry about it anyway. I did indeed mean that the property is redundant, and was advocating the smallest possible language. I still favour a small language, but I now accept that it needs to be supported by a rich library of convenient secondary properties in which controlled redundancy is acceptable. We don't need to talk of eliminating such constructs providing we can find a good way to express this language/library division. Simon ________________________________ From: Mike Beckerle [mailto:beckerle@us.ibm.com] Sent: 14 August 2007 14:24 To: dfdl-wg@ogf.org; Simon Parker Subject: Re: [DFDL-WG] Minutes from 2007-08-08 Call I forgot to clarify Simon's question on sp165. This was the 'finalTerminatorCanBeMissing" property. We considered the comment that this might be unnecessary. Use case: file of text format. Each "record" in the file is terminated by a CRLF so sez the user. At the top level this file contains an array of these records. The file might or might not have a CRLF at the end of the file because human beings might have edited the file with a text editor, and either inserted or neglected to insert this final CRLF. We want the file format to be legal with or without the final CRLF; however, all prior CRLFs in the file must be present. So how to express this: 1) CRLF is a terminator of the record 2) CRLF is an occursSeparator of the enclosing array, records have no terminator. We enclose the array in a sequence group where the array is followed by a hidden "optional" (minOccurs=0 max=1) element of fixed="CRLF" string value. Choice (1) requires that we have finalTerminatorCanBeMissing Choice (2) is just modeling the behavior that is required directly via hidden elements. This is tantamount to saying that this keyword is not worth having because there is a way to model it already. This is true of many keywords. If we deem this one too obscure, then we need to revisit many others. (Leading/Trailing Skip Bytes is a good example. Trivially represented by a hidden element). What are our criteria for inclusion? Up until now our criteria have been to include things that existing systems already have found a need for. However, existing systems don't have hidden field capability. Note that this same missing final terminator issue can come up not only with End-of-data, but with any bounded size structure. E.g., suppose we say that an array has occursUnits="bytes" and occursPath="874". Then it is 874 bytes long. The array elements can be terminated by a particular data. E.g., semicolon. For the same reasons as the CRLF example above, we want to be able to tolerate a missing final semicolon before the end of the 874 bytes. In effect the byte-length-limit creates an implicit "end-of-data" for a sub-stream consisting of just those bytes. Conclusion: finalTerminatorCanBeMissing seems to be useful enough and comes up often enough that I think the keyword is worthwhile. Implication: we should create a list of keywords or enumerated values for properties that we think are in the grey area where perhaps we want to drop them. Here's some candidates: byteOrderMarkPolicy, leading/trailingSkipBytes. Both these can be modeled readily as hidden elements. There are probably others. 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@us.ibm.com 508-599-7046 Mike Beckerle/Worcester/IBM 08/14/2007 08:40 AM To "Simon Parker" <simon.parker@polarlake.com> cc dfdl-wg@ogf.org Subject Re: [DFDL-WG] Minutes from 2007-08-08 CallLink <Notes://D01ML259/85256FDB00077D54/DABA975B9FB113EB852564B5001283EA/BD9C FD7CA73D7AFD852573360052302A> In conjunction with the annotated document these notes are clear, except for 'sp165'. Perhaps someone will recapitulate the discussion briefly at Wednesday's conference. I think only three annotations remain: sp167 Absent and missing (expanded discussion on the wiki already) This will be a major topic on a call. sp172 separatorType="infix" I'm happy to drop this strange stuff about separatorType=prefix or postfix and just say separator means infix. However, I would note that at least two major integration products (IBM WebSphere Transformation Extender - formerly Mercator, and Microsoft Biztalk, have this concept, so we may end up putting it back in. Presumably MS copied the earlier Mercator style, or both got it from common requirements in some EDI standard. sp173 defaultWhenMissing (expanded discussion on the wiki already) Same topic as sp167 above. Will have a call topic to discuss. I've added another contribution to the wiki discussion on 'require'. This seems to be at resolution I think, which is that we can express this using assertions. The general style of using DFDL to describe what fixed-data syntactic constructs look like is a good one. However, I've amended the Wiki thread on this with a further issue for group consideration. See bottom of page: https://forge.gridforum.org/sf/wiki/do/viewPage/projects.dfdl-wg/wiki/Re quire?_message=1187096164776 The 'length and occurs' proposal is an improvement, though I still have reservations to discuss; likewise the 'opaque data' proposal. For a call, this week or soon. I will send out an agenda. 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@us.ibm.com 508-599-7046 "Simon Parker" <simon.parker@polarlake.com> Sent by: dfdl-wg-bounces@ogf.org 08/13/2007 10:56 AM To <dfdl-wg@ogf.org> cc Subject Re: [DFDL-WG] Minutes from 2007-08-08 Call In conjunction with the annotated document these notes are clear, except for 'sp165'. Perhaps someone will recapitulate the discussion briefly at Wednesday's conference. I think only three annotations remain: sp167 Absent and missing (expanded discussion on the wiki already) sp172 separatorType="infix" sp173 defaultWhenMissing (expanded discussion on the wiki already) I've added another contribution to the wiki discussion on 'require'. The 'length and occurs' proposal is an improvement, though I still have reservations to discuss; likewise the 'opaque data' proposal. Regards, Simon ________________________________ From: dfdl-wg-bounces@ogf.org [mailto:dfdl-wg-bounces@ogf.org] On Behalf Of Mike Beckerle Sent: 08 August 2007 18:00 To: dfdl-wg@ogf.org Subject: [DFDL-WG] Minutes from 2007-08-08 Call MikeB, Geoff Judd, Alan Powell attended. Continued through SP's comments. sp37 - got it. sp45 - agree. This whole part to be rewritten. sp115 - ok. strict and "lax" as enums. No built-in default - we never use defaults in the processor itself. Only in the predefined formats. sp118 - ok sp123 - Proposal to simplify length, lengthKind, lengthUnits, and also occursKind, occursPath, occursPathUnits needed. (along the lines of byteCount, itemCount, length='delimited' enum, etc.) sp154 - Need specific proposal to eliminate hexBinary and use what for opaque (consider also string with encoding='bytes'. ) Or introduce a dfdl:byteString type or dfdl:opaque type. (derived type - just a standard name). sp158 - see sp123 sp165 - needed to have composition property for enclosing groups and or end-of-data. Regexp doesn't fix this. 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@us.ibm.com 508-599-7046 -- dfdl-wg mailing list dfdl-wg@ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg