The use cases for considering the inclusion of the recursive use of DFDL to define markup or other DFDL properties are: a) Case insensitivity of data (eg, true & TRUE for text boolean) b) Case insensitivity of markup (eg, hdr & HDR for initiator) c) Different possible values for non-white space markup (eg, @ and # for separator) d) Different possible values for data (eg, true & yes for text boolean) e) Encoding of markup different to encoding of data (eg, initiator and terminator different to data) The proposal is to use various existing mechanisms to handle all these use cases, and negate the need to include recursive use of DFDL in 1.0. a) Case insensitivity of data (eg, true & TRUE for text boolean) - Use a single flag dfdl:valueIgnoreCase to cover all affected properties - Properties: - dfdl:occursStopValue - dfdl:numberZeroRep - dfdl:nilValues - dfdl:textBooleanTrue - dfdl:textBooleanFalse b) Case insensitivity of markup (eg, hdr & HDR for initiator) - Use a single flag dfdl:valueIgnoreCase to cover all affected properties - Properties: - dfdl:initiator - dfdl:terminator - dfdl:separator c) Different possible values for non-white space markup (eg, @ and # for separator) - Use multi-value property. Propose that property name remains singular. - Properties: - dfdl:initiator - dfdl:terminator - dfdl:separator d) Different possible values for data (eg, true & yes for text boolean) - Use multi-value property. Propose that property name remains singular, so dfdl:nilValues becomes dfdl:nilValue singular. - Properties: - dfdl:occursStopValue - dfdl:numberZeroRep - dfdl:nilValues - dfdl:textBooleanTrue - dfdl:textBooleanFalse e) Encoding of markup different to encoding of data (eg, initiator and terminator different to data) - Use <xs:sequence> to wrap the element and carry the markup, for example: <sequence dfdl:encoding="ascii" dfdl:separator=":"> <sequence dfdl:encoding="ebcdic" dfdl:initiator="VAL" dfdl:terminator="END"> <element name="val" type="..." dfdl:encoding="ascii" /> </sequence> </sequence> - This should be able to handle all cases of what is a rare occurrence anyway, and still allows speculative parsing rules to apply. - Alternative is to treat the markup as a value (the EDI scenario) - this is the subject of a separate action 026, which will be solved using variables or another technique, but not by using DFDL recursively. There are some other properties to which cases a), b), c), d) could apply. We need to decide whether or not case sensitivity and/or multi-values are appropriate to these: - dfdl:textPadChar - dfdl:escapeCharacter - dfdl:escapeForEscapeCharacter - dfdl:escapeBlockStart - dfdl:escapeBlockEnd - dfdl:numberGroupSeparator - dfdl:numberDecimalSeparator - dfdl:numberExponentCharacter - dfdl:numberInfinityRep - dfdl:numberNanRep Regards Steve Hanson Programming Model Architect WebSphere Message Brokers Hursley, UK Internet: smh@uk.ibm.com Phone (+44)/(0) 1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 09/06/2009 13:27 ----- Steve Hanson/UK/IBM@IBMGB Sent by: dfdl-wg-bounces@ogf.org 15/04/2009 13:47 To dfdl-wg@ogf.org cc Subject [DFDL-WG] Recursive use of DFDL for variable markup - use case
From last week's call:
7. Recursive use of DFDL for variable markup Use of a DFDL annotated element/type to describe an initiator, length prefix, terminator, separator, etc. Steve suggested the most important use of "variable markup-like mechanism" in IBM's WTX product is to reference a location earlier in the bit stream where a delimiter value is found. We handle this already by use of a path expression. The additional variable markup mechanism was to avoid proliferation of keywords for various corner cases on initiator, terminator and separator. Eg., what if you want the initiator to be "Name" or "name" only, not "NAME", "nAmE", etc. So case insensitive is not expressive enough. This can always be modeled, just not as an initiator tag. Feeling was to leave out variable markup (other than for prefix lengths) for v1.0, and to propose the minimum set of extra properties that can be used to address the common use cases, but that IBM needed to see whether this satisfied all WTX use cases. Regards Steve Hanson Programming Model Architect WebSphere Message Brokers Hursley, UK Internet: smh@uk.ibm.com Phone (+44)/(0) 1962-815848 -- dfdl-wg mailing list dfdl-wg@ogf.org http://www.ogf.org/mailman/listinfo/dfdl-wg 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