November 2014 - dfdl-wg - lists.ogf.org

still no need for fn:error
by Mike Beckerle 03 Aug '16

03 Aug '16

Here's the example as suggested by Jonathan of how to issue an error that I previously was suggesting needed fn:error. I'm convinced this is sufficient and we can avoid the need for fn:error now. <xs:element name="magic_number" type="ex:uint32" dfdl:byteOrder="bigEndian"> <xs:annotation> <xs:appinfo source="*http://www.ogf.org/dfdl/*<http://www.ogf.org/dfdl/dfdl-1.0/> "> <dfdl:assert test="{ (xs:unsignedInt(.) eq *dfdl:hUInt('0xa1b2c3d4')*) | (xs:unsignedInt(.) eq *dfdl:hUInt('0xd4c3b2a1')*) }" message="{ fn:concat( 'Magic number ', dfdl:hexBinary(dfdl:unsignedInt(.)), ' was not 0xA1B2C3D4 (for bigEndian) or 0xD4C3B2A1 (for littleEndian).' }" /> <dfdl:setVariable ref="ex:bOrd">{ xs:unsignedInt(.) }<dfdl:setVariable> </xs:appinfo> </xs:annotation> </xs:element> -- Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com

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Fw: Fw: Action 248 (was Thoughts on a discriminator scenario)
by Steve Hanson 26 Nov '14

26 Nov '14

This action was raised because of concern with the behaviour of the discriminator in the following example. Because OCK is 'implicit' the 1st occurrence is not an actual PoU but the other 9 occurrences are. This means that for 1st occurrence, the discriminator actually acts on a higher PoU if one exists. <xs:element name="Type1" maxOccurs="10" dfdl:occursCountKind="implicit"> <dfdl:discriminator test="{fn:exists(A)}" /> <xs:complexType> <xs:sequence> <xs:element name="A" dfdl:initiator="A:" ... /> <xs:element name="B" dfdl:initiator="B:" ... /> <xs:element name="C" dfdl:initiator="C:"... /> </xs:sequence> </xs:complexType> This led to the suggestion that a discriminator should not 'leak' beyond a potential PoU, regardless of whether it is an actual PoU. The argument for this is contained in the thread below, and on re-reading I still think it is the best solution to this, so that is what I propose. There were also issues about the wording in section 9.3.3. Sections 9.3.3 and 7.4 are reproduced below, and updated to address the wording and leaking issues. ------------------------------------------------- 9.3.3 Points of Uncertainty A point of uncertainty occurs when parsing a schema component when an occurrence of that schema component might not be the next item encountered in the data stream. Points of uncertainty can be nested. Any one of the following schema constructs is a potential point of uncertainty: · A branch of xs:choice · All xs:elements in an unordered xs:sequence (dfdl:sequenceKind is 'unordered') · An optional xs:element · An array xs:element. · All xs:elements in an xs:sequence containing one or more floating xs:elements. The parser resolves these points of uncertainty by way of a set of construct-specific rules given below along with determining whether schema components are known-to-exist or known-not-to-exist. For some of these constructs, whether there is an actual point of uncertainty depends on the representation of the constructs in the data. A branch of xs:choice is always a point of uncertainty. A choice is resolved sequentially, or by direct dispatch. Sequential choice resolution occurs by parsing each choice branch in schema definition order until one is known-to-exist. It is a processing error if none of the choice branches are known-to-exist. Direct-dispatch choice resolution occurs by matching the value of the dfdl:choiceDispatchKey property to the value of the dfdl:choiceChoiceBranchKey property of one of the choice branches. It is a processing error if none of the choice branches have a matching value in their dfdl:choiceChoiceBranchKey property. An element in an unordered xs:sequence is always a point of uncertainty. It is resolved by parsing for the child components of the sequence in schema definition order at each point in the data stream where a component can exist until the required number of occurrences of each child component is known- to-exist or the sequence is terminated by delimiters or specified length. An element in a sequence with one or more floating elements is always a point of uncertainty. It is resolved by parsing for the expected element at that point in the data stream. If the expected element is known-not-to-exist then an occurrence of each floating element is parsed in schema definition order. When parsing an array, points of uncertainty only occur for certain values of occursCountKind, as follows: occursCountKind Details of Point of Uncertainty fixed No point of uncertainty (maxOccurs occurrences expected). implicit A point of uncertainty exists after minOccurs occurrences found and until maxOccurs found. parsed A point of uncertainty exists for all occurrences expression No point of uncertainty (occursCount occurrences expected) stopValue No point of uncertainty (stopValue must always be present, even when minOccurs is 0). Table 11: Points of Uncertainty and dfdl:occursCountKind An optional element point of uncertainty is resolved by parsing the element until it is either known-to-exist or known-not-to-exist. Whether an optional element is an actual point of uncertainty depends on property dfdl:occursCountKind as described above. (Property dfdl:occursCountKind is defined in Section 16.1 dfdl:occursCountKind property.) For an array element, the point of uncertainty is resolved for each occurrence separately by parsing the occurrence until it is either known-to-exist or known-not-to-exist. Note that a discriminator defined on, or contained by, a schema construct that is a potential point of uncertainty, will only ever resolve that point of uncertainty. For example, if a discriminator is defined on an array element which is contained within the branch of a choice, the discriminator will only resolve the existence of occurrences of the array element, and never the existence of the occurrence of the choice branch. This is true even when a potential point of uncertainty is not an actual point of uncertainty. ------------------------------------ 7.4 The dfdl:discriminator Statement Annotation Element DFDL discriminators are used during parsing to resolve points of uncertainty that cannot be resolved by speculative parsing. Discriminators are not used during unparsing. They can also be used to force a resolution earlier during the parsing of a group so that subsequent parsing errors are treated as processing errors of a known component rather than a failure to find a component. A discriminator determines the existence or non-existence of a component. If the discriminator is successful then the component is known to exist and any subsequent errors will not cause backtracking at points of uncertainty. If a discriminator is unsuccessful then the component is known not to exist and backtracking occurs immediately. If the complex type of an element contains a sequence group as its content model then if the sequence group is known not to exist, then the element is known not to exist. Examples of dfdl:discriminator annotation are below : <dfdl:discriminator> { ../recType eq 0 } </dfdl:discriminator> <dfdl:discriminator test="{ ../recType eq 0}" /> When the discriminator's expression evaluates to "false", then it causes a processing error, and the discriminator is said to fail. A discriminator defined on, or contained by, a schema construct that is a potential point of uncertainty, will only ever resolve that point of uncertainty. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 17/11/2014 11:54 ----- From: Steve Hanson/UK/IBM To: Tim Kimber/UK/IBM@IBMGB Cc: dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Date: 15/05/2014 10:48 Subject: Re: [DFDL-WG] Fw: Action 248 (was Thoughts on a discriminator scenario) Tim - I've responded to your specific comments below in blue font. All - You will see that I have some concerns over the words used in the definition of a PoU, as we seem to be unclear as to whether a PoU is a point in the data stream or a point in the model. I am wondering whether the concepts of 'potential PoU' and 'actual PoU' can be better expressed as 'PoU in the model' and 'PoU in the data'. I want to mull this over for a while. I'm not changing the rules by this, just how we express them. So please let me run with this before replying. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Tim Kimber/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org, Date: 14/05/2014 23:31 Subject: Re: [DFDL-WG] Fw: Action 248 (was Thoughts on a discriminator scenario) Sent by: dfdl-wg-bounces(a)ogf.org I agree that the wording is not easy to get right. However, I think the current wording needs some adjustment so I'm going to make some suggestions and see where it leads. "A point of uncertainty occurs in the data stream when there is more than one schema component that might occur at that point." I don't think this is precise enough. SMH: Agree. I need to think about this sentence. There are several things potentially wrong. It is defining a PoU as occurring in the data stream, whereas elsewhere PoU is equated to a position in the model. It says 'more than one schema component that might occur' - maybe it should say 'a schema component may or may not occur'. And schema components don't occur in the data stream anyway - occurrences of them do. - if an optional element occurs at the end of the input data then there is only *one* schema component that might occur at that point. The end of the data stream might occur instead. SMH: Yes but I I raised some similar arguments earlier in the thread, about the last branch of a choice not being a PoU, or the last element in an unordered sequence when all the others had been found not being a PoU. We agreed that these are still all treated as PoUs for clarity. This is another example. - if an optional element occurs before the last required element in a sequence AND the separatorSuppressionPolicy is not 'anyEmpty' then there is exactly one schema component that can occur at that point in the data stream. But it might be 'empty', in which case it will not be put into the info set. This is not pedantry. The parser will never need to backtrack in either of these cases and in the second case it is obvious in advance which schema component the parser should select for parsing. SMH: We have agreed in the past that the presence of a separator is not enough to infer 'known-to-exist', so separators should not be brought into this definition. You are right that in a positional sequence the parser is looking for an occurrence of a component or its empty rep, and never an occurrence of the next schema component, so the parser can certainly optimise here. Let's take any discussion of separators out of this for the moment, and raise a separate action if needed. Points of uncertainty can be nested. Any one of the following constructs is a potential point of uncertainty: 1. An xs:choice 2. All xs:elements in an unordered xs:sequence (dfdl:sequenceKind is 'unordered') 3. An optional xs:element 4. An array xs:element. 5. All xs:elements in an xs:sequence containing one or more floating xs:elements. 1. should say 'A member of an xs:choice' because it is the member, not the group itself, that is the point of uncertainty. I think the confusion has arisen because only one member of a choice group can exist in the data. So if any member exists, it automatically ends any speculation about the content of the choice group. But I insist that the real point of uncertainty is the member. A choice group is always 'known to exist' because according to DFDL rules it must have minOccurs=maxOccurs=1. FWIW, I have no problem with talking about 'resolving a choice', provided that we define that as 'Determining which member of a choice group ( if any ) is known to exist in the data'. SMH: I agree that it should say member. 2. Should say 'All members of an unordered xs:sequence' to keep the language consistent with 1. The section on unordered groups clearly restricts members to elements only. SMH: No. Using 'xs:element' is consistent with optionals & arrays in 3 and 4, which are also always elements. so xs:element is more consistent. 3. See above - an optional elements is not always a 'point of uncertainty' according to the literal definition that we are currently using. SMH; Right, but the bullets are defining potential PoUs, so it is correct as it stands. 4. Should say 'An optional occurrence of an array element, unless the separator properties make it a positional array and the occurrence is required in the data' SMH: No. All occurrences can be PoUs, it depends on OCK. And separators do not resolve PoUs as noted. This definition 4 is the one that is key for Action 248, which is ultimately what led to this discussion and what needs to be resolved. The question is whether 4 should say a) all arrays are potential PoUs as it does now, or b) just some arrays are potential PoUs depending on OCK. Whatever we choose, a discriminator within that array must not leak beyond the array as explained below in bold red font. I think a) is clearer and we can then make a general statement about discriminators not leaking outside of any potebtial PoU. If we adopt b) then we need a separate statement about discriminators and arrays, which seems more bitty. 5. Should say 'All members...' for consistency. SMH: See 3. regards, Tim Kimber, IBM Integration Bus Development (Industry Packs) Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 37246742 From: Steve Hanson/UK/IBM@IBMGB To: , Date: 13/05/2014 10:28 Subject: [DFDL-WG] Fw: Action 248 (was Thoughts on a discriminator scenario) Sent by: dfdl-wg-bounces(a)ogf.org This will be discussed on today's call. Please have a position on the paragraph below that ends 'What do others think?' Thanks Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 13/05/2014 10:19 ----- From: Steve Hanson/UK/IBM To: Tim Kimber/UK/IBM@IBMGB, Cc: dfdl-wg(a)ogf.org Date: 30/04/2014 12:25 Subject: Re: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) Tim Responses below. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Tim Kimber/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org, Date: 11/04/2014 14:03 Subject: Re: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) Sent by: dfdl-wg-bounces(a)ogf.org "2. If a potential point of uncertainty is sometimes an actual point of uncertainty (ock 'implicit') then a discriminator that applies it will only ever resolve, or have no effect on, that point of uncertainty. It never has an effect on any enclosing point of uncertainty." This could be misinterpreted. The discriminator could evaluate to 'false' and thus cause the POI to be resolved negatively ( the component would be 'known not to exist' ) SMH: Agree, and I can improve the words here. 1. and 3. will both apply if an element with ock='fixed' appears as a choice branch. Is the POI always an actual POI or never? SMH: No. There are two independent points of uncertainty, the choice branch and the array. The wording of 3. reads very strangely. 'If a potential point of uncertainty is never an actual point of uncertainty' begs the question 'why is it even a potential point of uncertainty?'. The current wording follows from our definition of the term 'point of uncertainty': "A point of uncertainty occurs in the data stream when there is more than one schema component that might occur at that point." Points of uncertainty can be nested. Any one of the following constructs is a potential point of uncertainty: 1. An xs:choice 2. All xs:elements in an unordered xs:sequence (dfdl:sequenceKind is 'unordered') 3. An optional xs:element 4. An array xs:element. 5. All xs:elements in an xs:sequence containing one or more floating xs:elements. I think this definition is too broad. It forces us to discuss potential POUs that will never be actual POUs according to the first sentence. SMH: Yes it does read a bit strangely, but there's a reason for this. If we said that ock 'fixed', 'expression' or 'stopValue' are never POUs then what does it mean if a discriminator is placed on such an element? A discriminator gets evaluated for each occurrence of an array. For that reason we can not let a discriminator within an array leak beyond the array - regardless of whether it is a POU or not - otherwise what does that mean to enclosing POUs? So even if we said that ock 'fixed', 'expression' or 'stopValue' are never POUs we would still need the spec to state that a discriminator never leaks beyond them. I think it is clearer to say that a discriminator never leaks beyond a potential POU and keep the existing definition. What do others think? regards, Tim Kimber, IBM Integration Bus Development (Industry Packs) Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 37246742 From: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org, Date: 11/04/2014 11:44 Subject: Re: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) Sent by: dfdl-wg-bounces(a)ogf.org 248 Discriminators and potential points of uncertainty (Steve) 28/1: Steve to write up a proposal to prevent a discriminator from behaving in a non-obvious manner when used with a potential point of uncertainty that turns out not to be an actual point of uncertainty. 5/2: Steve sent an email to check whether choice branches, unordered elements and floating elements should always be actual points of uncertainty, as there are times when there is no uncertainty, eg, last choice branch; all floating elements found. It was decided that they are always actual points of uncertainty. To do otherwise will complicate implementations and result in fragile schemas. Steve will proceed with the proposal on that basis. Based on the above, which reflects the email discussion below, here is what I propose to resolve this action. 1. If a potential point of uncertainty is always an actual point of uncertainty (choice branch, element in unordered sequence, floating element, ock 'parsed') then a discriminator that applies to it will only ever resolve that point of uncertainty. It never has an effect on any enclosing point of uncertainty. 2. If a potential point of uncertainty is sometimes an actual point of uncertainty (ock 'implicit') then a discriminator that applies it will only ever resolve, or have no effect on, that point of uncertainty. It never has an effect on any enclosing point of uncertainty. 3. If a potential point of uncertainty is never an actual point of uncertainty (ock 'fixed', 'expression', 'stopValue') then a discriminator that applies to it will never have an effect on that point of uncertainty. Nor does it ever have an effect on any enclosing point of uncertainty. I think 1 and 2 are not controversial, but there is an alternative for 3: 3. If a potential point of uncertainty is never an actual point of uncertainty (ock 'fixed', 'expression', 'stopValue') then a discriminator that applies to it will never have an effect on that point of uncertainty. Instead the discriminator is applied to any enclosing point of uncertainty. The alternative means that changing an element from (say) ock 'parsed' to ock 'expression' has the same effect on a discriminator as changing the element to (1,1). The discriminator that applied to it now applies to any enclosing pou. SMH: Afternote: The alternative does not work for the reason given in my reply to Tim above. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Tim Kimber/UK/IBM@IBMGB, Cc: dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Date: 05/02/2014 12:04 Subject: Re: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) Thanks Tim, all good points. Comments to your comments. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Tim Kimber/UK/IBM To: Steve Hanson/UK/IBM@IBMGB, Cc: dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Date: 05/02/2014 11:01 Subject: Re: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) A couple of comments below. regards, Tim Kimber, IBM Integration Bus Development (Industry Packs) Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 37246742 From: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org, Date: 05/02/2014 10:50 Subject: [DFDL-WG] Action 248 (was Thoughts on a discriminator scenario) Sent by: dfdl-wg-bounces(a)ogf.org 248 Discriminators and potential points of uncertainty (Steve) 28/1: Steve to write up a proposal to prevent a discriminator from behaving in a non-obvious manner when used with a potential point of uncertainty that turns out not to be an actual point of uncertainty. 5/2: With Steve I started on this by reading section 9.3.3 on points of uncertainty, which lists the potential PoUs. Here's the list to save getting the spec out. 1. An xs:choice branch 2. All xs:elements in an unordered xs:sequence (dfdl:sequenceKind is 'unordered') 3. An optional xs:element 4. An array xs:element 5. All xs:elements in an xs:sequence containing one or more floating xs:elements. The section then looks at each in turn and gives the circumstances when it is an actual PoU or not. As currently written, it is only 3 and 4 where a potential PoU might not be an actual PoU. For 1, 2 and 5 it says they are always actual PoUs. But I'm not sure that's correct. A deeper analysis of what is actually going on with 1, 2 and 5 says to me that there are times when there might not be an actual PoU. 1. Given that there is no concept in DFDL of optional choice branches, then if the last branch is reached then there is no longer a PoU. It must be that branch else it is a processing error. TK: I think of it slightly differently. It is a PoU, even if the branch is the only remaining branch. If we say that the final choice branch is not a PoU then diagnostics become confused - the parser reports the error code as 'error while parsing root/choice/lastBranch/field1' when the correct error code would be 'none of the branches of root/choice were found in the data'. SMH: I see your point. My thinking was that choices have finite branches and a choice is (1,1). If I have got to the last branch then I am not one of the other branches so I must be this one. If there is any other possibility then the model is missing a branch, even if it is just one that contains an empty sequence with an assert {fn:false()}. In practice of course users forget to add that last branch (there's no XSDL equivalent to the 'default' branch of a switch/case statement), so yes they could end up with an unclear diagnostic. 2. There can come a point in an unordered sequence when all that can be encountered is one element, and if that is (1,1) then there is no longer a PoU. TK: It's still a PoU. The specification says that occursCountKind is 'parsed' for all members of an unordered group, so min/maxOccurs do not come into play. SMH: Interesting. The spec says that if a member is optional or an array then it must be 'parsed'. If it is (1,1) though it does not have an occursCountKind. The specific case I was thinking of is when all members are (1,1), so when you have one element to go there is no PoU. However, the rewrite into a repeating choice has the effect of making everything 'parsed', which is really the point you are making. So I agree with you, it is easier to say that everything is an actual PoU else it complicates the rewrite semantic. 5. If all floating elements are (1,1) and all are encountered, then from that point on there are no longer any PoUs due to floating elements. TK: I suspect that floating elements are somewhat like unordered branches - most users will not want min/maxOccurs to affect the parsing of the group. Schema validation ( or more complex validation applied in the receiving application ) will deal with non-conformances. SMH: Possibly yes. With something like X12 NTE segments, that is the case. But we don't express the floating semantic as a rewrite of the whole sequence like we do for unordered, it's more of a per element thing. And if that is done dynamically as we go through the sequence, having no PoU can result. I'd like us to get straight on this before I proceed with the action proper. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 05/02/2014 10:12 ----- From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org, Date: 27/01/2014 17:39 Subject: Fw: Thoughts on a discriminator scenario Been thinking some more on the discriminator scenario below that I mailed out before xmas, and discussing it with the IBM DFDL team. The 'confusing' aspect of the behaviour is that a discriminator within a potential PoU will act on a higher level PoU if the potential PoU is not an actual PoU. In the example, the array element 'Type1' is not an actual PoU for occurrence 1, only for occurrences 2+. So when the discriminator fires for occurrence 1 it will resolve a higher level unresolved PoU if one exists. Perhaps the spec should say that a discriminator can't 'leak' beyond the potential PoU that encloses it ? If so, then for occurrence 1 the discriminator has no effect, and only has an effect for occurrences 2+. This makes for more predictable and robust schemas. We'd need to go through spec section 9.3.3 carefully to see if this does not break any of the potential PoUs that are listed. Regards Steve Hanson Architect, IBM Data Format Description Language (DFDL) Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 16/01/2014 09:55 ----- From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org, Date: 20/12/2013 13:20 Subject: Thoughts on a discriminator scenario Take the following schema (simplified) for element Type1 (1,10) being a loop for elements A,B,C. Type 1 does not have an initiator so I need to use a discriminator to establish the existence of an occurrence of Type1 so that incorrect backtracking does not occur after an error. Because occursCountKind is 'implicit', the 1st occurrence is not a point of uncertainty so the discriminator acts instead on any enclosing point of uncertainty, but for 2nd and subsequent occurrences it acts on Type1. That is all working as designed, but I think users find will the 1st occurrence behaviour a bit confusing. There are workarounds to avoid the problem, eg, use occursCountKind 'parsed' or split Type1 into two as (1,1) and (0,9). I think this is worth documenting in a tutorial as this is quite subtle stuff. <xs:element name="Type1" maxOccurs="10" dfdl:occursCountKind="implicit"> <dfdl:discriminator test="{fn:exists(A)}" /> <xs:complexType> <xs:sequence> <xs:element name="A" dfdl:initiator="A:" ... /> <xs:element name="B" dfdl:initiator="B:" ... /> <xs:element name="C" dfdl:initiator="C:"... /> </xs:sequence> </xs:complexType> Regards Steve Hanson Architect, IBM Data Format Description Language (DFDL) Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 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 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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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

2 4

glossary entry for "fixed length" needed.
by Mike Beckerle 26 Nov '14

26 Nov '14

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php>

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OGF DFDL WG Call Minutes 2014-11-25
by Steve Hanson 26 Nov '14

26 Nov '14

Please find minutes from the above call at http://redmine.ogf.org/dmsf_files/13377?download= ** Updated DFDL 1.0 specification published at http://www.ogf.org/documents/GFD.207.pdf. ** Regards Steve Hanson Architect, IBM DFDL, Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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Fw: Action 272: Catch 22.for EVDP & NVDP ?
by Steve Hanson 26 Nov '14

26 Nov '14

Spec updates in this tracker http://redmine.ogf.org/issues/245. Note that a fixed length element with length 0 can have an empty representation, it's only those that have non-zero length that can't. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 26/11/2014 10:28 ----- From: Steve Hanson/UK/IBM@IBMGB To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 18/11/2014 17:49 Subject: Re: [DFDL-WG] Action 272: Catch 22.for EVDP & NVDP ? Sent by: dfdl-wg-bounces(a)ogf.org Review for next call please. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com>, DFDL-WG <dfdl-wg(a)ogf.org> Date: 28/10/2014 14:48 Subject: Re: [DFDL-WG] Catch 22.for EVDP & NVDP ? Thinking through the implications of having EVDP not apply if content length can not be zero: 1) Cases are dfdl:lengthKind 'explicit', dfdl:length not an expression and not zero, and (simple only) dfdl:lengthKind 'implicit' and maxLength facet not zero. 2) Does it mean a) that there is no concept of an empty representation, or b) that there is but it is not subject to EVDP and 'effective' EVDP is 'none' ? - If b) that does not fix the issue around initiatedContent, - if a) it means not finding the element must be taken as missing which implies no default value can be applied. Hmm 3) What about NVDP ? Should we be disallowing the use of %ES; as a nil value for these cases as well ? Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 17/09/2014 15:44 Subject: Re: [DFDL-WG] Catch 22.for EVDP & NVDP ? Having thought this through I think that you are correct. If the content length can never be 0 then EVDP does not apply. I think IBM DFDL is issuing an error when it should not be. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Steve Hanson/UK/IBM@IBMGB, Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 09/09/2014 15:37 Subject: Re: [DFDL-WG] Catch 22.for EVDP & NVDP ? Interesting. To me if lengthKind is explicit, and non-variable (i.e., is fixed length), then EVDP doesn't apply, because by definition, such a representation is not ever empty. I would assume that EVDP would be ignored in such a case, and an implementation might even generate warnings if dfdl:emptyValueDelimiterPolicy appeared directly on such an element or simpleType where a fixed length is also expressed. This is one of the challenges that having lengthKind 'explicit' which handles both the fixed length, and variable-length using an expression, creates. Even though we don't have a lengthKind 'fixed', we still have fixed-length as a concept, and some other features interact with fixed length, like empty values. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Tue, Sep 2, 2014 at 10:31 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: <xs:element name="choiceGroup" dfdl:lengthKind="implicit"> <xs:complexType> <xs:choice dfdl:choiceLengthKind="implicit" dfdl:initiatedContent="yes"> <xs:element name="myNum1" type="xs:int" dfdl:lengthKind="explicit" dfdl:length="2" dfdl:textNumberPattern="#0" dfdl:initiator="num:" dfdl:terminator="~" /> > <xs:element name="myText1" type="xs:string" dfdl:lengthKind="explicit" dfdl:length="2" dfdl:initiator="text:" dfdl:terminator="~" /> </xs:choice> </xs:complexType> </xs:element> The above model is a choice of two elements, each of which is fixed length and has an initiator and terminator. Because the elements are fixed length, I must set dfdl:emptyValueDelimiterPolicy (EVDP) to be 'none' **. I also want to discriminate using the initiator, so I set dfdl:initiatedContent 'yes' on the choice, so I must set EVDP to 'initiator' or 'both' ++. (Same for NVDP if nillable). Catch 22. ** 'none' because the only valid empty representation is that there is nothing there at all. The element is fixed length X, so if the delimiters are present then the content must be length X and can't be zero length. ++ 'initiator' or 'both' because an initiator must always be present when dfdl:initiatedContent 'yes'. The implication is that I can't use dfdl:initiatedContent for this choice. While I can switch off nillable to avoid the error with NVDP, there is no other way of avoiding the EVDP error. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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

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Re: [DFDL-WG] Fw: Fw: Action 260
by Steve Hanson 25 Nov '14

25 Nov '14

http://redmine.ogf.org/issues/243 Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 19/11/2014 10:55 Subject: Re: [DFDL-WG] Fw: Fw: Action 260 Agreed on the WG call that the behaviour in the table below will be adopted including the restrictions for OCK 'parsed'. List of spec changes as a result of this action are below. Note that the behaviour for OCK 'stopValue' in the table was not correct for unparsing. SSP 'anyEmpty' has a different behaviour than the others - it causes zero-length occurrences not to be output - which is fine. Please review so we can close on next call. 1) 14.2 - updates to paragraphs that describe positional and non-positional sequences Positional sequence - Each occurrence in the sequence can be identified by its position in the data. Typically the components of such a sequence do not have an initiator. In some such sequences, the separators for optional zero-length occurrences may or must be omitted when at the end of the group. In DFDL, a sequence is considered positional if it contains only required elements and/or optional and array elements that have dfdl:occursCountKind 'implicit', 'fixed' or 'expression', and it has dfdl:separatorSuppressionPolicy 'never', 'trailingEmptyStrict' or 'trailingEmpty'. Non-positional sequence - Occurrences in the sequence cannot be identified by their position in the data alone. Often the components of such a sequence have an initiator. Such sequences sometimes allow the separator to be omitted for optional zero-length occurrences anywhere in the sequence. Speculative parsing might need to be employed by to identify each occurrence. In DFDL, a sequence is non-positional if it contains any optional or array elements that have dfdl:occursCountKind 'parsed' or 'stopValue', and/or it has dfdl:separatorSuppressionPolicy 'anyEmpty'. 2) 14.2.2 - updates to the last sentences of the 'When dfdlk:occursCountKind is ...' paragraphs to match the table and notes below. When an element is required and is not an array then one occurrence is always expected along with its separator. The dfdl:separatorSuppressionPolicy of the sequence has no effect (nothing is eligible for suppression). Otherwise the behaviour is dependent on dfdl:occursCountKind. When dfdl:occursCountKind is 'fixed' then XSDL minOccurs must equal maxOccurs and that many occurrences are always expected along with their separators. The dfdl:separatorSuppressionPolicy of the sequence has no effect (nothing is eligible for suppression). When dfdl:occursCountKind is 'expression' the number of occurrences is given by dfdl:occursCount and exactly that many occurrences are always expected along with their separators. The dfdl:separatorSuppressionPolicy of the sequence has no effect (nothing is eligible for suppression). When dfdl:occursCountKind is 'parsed' any number of occurrences and their separators are expected. The dfdl:separatorSuppressionPolicy of the sequence must be 'anyEmpty' and it is a schema definition error otherwise. When dfdl:occursCountKind is 'stopValue', any number of occurrences and their separators are expected followed by the stop value and its separator. The dfdl:separatorSuppressionPolicy of the sequence has no effect. When dfdl:occursCountKind is 'implicit', between XSDL minOccurs and maxOccurs (inclusive) occurrences and their separators are expected, according to the dfdl:separatorSuppressionPolicy of the sequence. 3) 14.2.3 - updates to the last sentences of the 'When dfdlk:occursCountKind is ...' paragraphs to match the table and notes below. When an element is required and is not an array then one occurrence is always output along with its separator. The dfdl:separatorSuppressionPolicy of the sequence has no effect (nothing is eligible for suppression). Otherwise the behaviour is dependent on dfdl:occursCountKind. When dfdl:occursCountKind is 'fixed' or 'expression' the occurrences in the augmented Infoset are always output along with their separators. The dfdl:separatorSuppressionPolicy of the sequence has no effect (nothing is eligible for suppression). When dfdl:occursCountKind is 'parsed' non zero-length occurrences in the augmented Infoset are output along with their separators. The dfdl:separatorSuppressionPolicy of the sequence must be 'anyEmpty' and it is a schema definition error otherwise. When dfdl:occursCountKind is 'stopValue' the occurrences in the augmented Infoset are output along with their separators followed by the stop value and its separator, according to the dfdl:separatorSuppressionPolicy of the sequence. When dfdl:occursCountKind is 'implicit' the occurrences in the augmented Infoset are output along with their separators, according to the dfdl:separatorSuppressionPolicy of the sequence. 4) 16 - update to occursStopValue property description The property is a list of logical values, so need to add: "The dfdl:stopValue property must not be empty string." Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 18/11/2014 12:23 Subject: Re: [DFDL-WG] Fw: Fw: Action 260 Mike Comments in-line. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Steve Hanson/UK/IBM@IBMGB Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 17/11/2014 23:11 Subject: Re: [DFDL-WG] Fw: Fw: Action 260 So I looked into what would be changed in the spec to make the adjustment suggested in this email thread, in intent. Rewriting the section is very undesirable at this stage for DFDL, so I was looking for incremental changes. What I came up with is this. In section 14.2.2 simply drop the sentences that mention this idea of an implied SSP, because they suggest the need to reconcile conflicting behaviors in the mixed case. I.e., drop all "The dfdl:separatorSuppressionPolicy is not applicable and the implied behaviour is '....'." With the omission of these sentences, the notion of an implied separator suppression policy that conflicts with one on the sequence goes away. There is only the SSP property of the sequence, and it is either relevant to the decision of whether to expect an item and its separator, or it isn't. The current descriptions in 14.2.2 of the behavior around suppression for each occursCountKind seem to be correct and match the table in this email thread, except for parsed. I'm not sure I agree with the assertion in this email thread that ock parsed only makes sense with "anyEmpty" behavior. We currently say in the spec that it has anyEmpty behavior, but if we drop that sentence (per suggestion above), then we would be loosening the behavior to allow empty elements in some cases. SMH: The intent of the table is that it is a schema definition error if 'parsed' and not 'anyEmpty' Suppose: <sequence dfdl:separatorSuppressionPolicy="trailingEmpty" dfdl:separator="|" dfdl:separatorPosition="infix" dfdl:terminator="%NL;"> <element name="a" type="xs:string" maxOccurs="unbounded" dfdl:occursCountKind='parsed'/> </sequence> In this case, the array is declared last in its sequence. The occurrences will all be element a, so this is positional. The number of them is determined by OCK parsed, and if enabled, validation will check, in this case, that at least 1 occurrence (the default for minOccurs) appears. In this case, empty string is a legal value, and we're not strict about trailing separators, so data like: 5|6|7|| is fine isn't it? The 'parsed' means you'll get 2 more empty string elements for the array when parsing that will not be re-created when unparsing, as they would be suppressed. I believe that is ok. There are many formats that can have that sort of asymmetry. SMH: To be clear, 'anyEmpty' already allows empty content when parsing, it has a lax semantic Change the above example to SSP trailingEmptyStrict, and now: 5,6,7||9 Now makes sense and you get one empty string in position 4. On unparsing this empty string would even get written out. I agree 'parsed' and SSP 'never' don't make sense together (as they don't for OCK implicit - SMH: only if maxOccurs 'unbounded' - see table 18 in 14.2.2), but the other 3 SSPs seem ok to me for declared-last elements. OCK parsed behaves (w.r.t. suppression, and ignoring defaulting and validation) just like OCK implicit with minOccurs 0 and maxOccurs 'unbounded'. (SMH: To be clear, defaulting and validation are independent of OCK). If we want to preserve the current restriction that parsed behaves like 'anyEmpty', then we can stipulate that when OCK is 'parsed', any number of non-empty occurrences and their separators are expected. (I would not be in favor of this.) SMH: So what you are saying is that 'parsed' is same as 'implicit' (0..unbounded). There are circumstances when this combination gives a schema definition error, as per Table 18 in 14.2.2 - this must therefore be the same for 'parsed'. It turns out that you only end up adding one extra legal behaviour for 'parsed', namely where element is declared last and SSP is 'trailingEmpty/Strict'. That's the example you quote above, but it's the only one. So is it buying much? SMH: When IBM put the table below together and said 'parsed' and SSP <> 'anyEmpty' is an error, it was to prevent a subtle change in behaviour for existing schemas with 'trailingEmpty/Strict'. Today the behaviour is 'anyEmpty', in the future it would be 'trailingEmpty/Strict'. Hence making it an error. As already noted in this thread, we also should add a sentence to stopValue: "The dfdl:stopValue property must not include empty string." The net result of these changes still isn't all that great, but it does remove one source of confusion - the 'implied' SSP conflict. SMH: If your 'parsed' proposal is adopted, you would need to document the 'parsed' behaviour as some combinations are schema definition errors. Arguably you would need the equivalent of Tables 18 and 19. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Mon, Oct 13, 2014 at 10:08 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: IBM has discussed this issue at some length internally, and come to the conclusion that the optional and array elements in a sequence should follow the separator suppression policy (SSP), and not have an implied SSP which is at odds with the sequence's SSP. In the table below, cells marked with a cross imply a schema definition error, and cells marked ok imply that there is a behaviour of the element for that OCK which is in keeping with the SSP of the sequence. SSP (1) OCK fixed implicit expression parsed stopValue (2) never ok ok ok x (5) ok (6) trailingEmpty trailingEmptyStrict ok (3) ok ok (4) x (5) ok (6) anyEmpty ok (3) ok ok (4) ok ok Notes: (1) SSP property applies only to an ordered sequence. An unordered sequence assumes 'anyEmpty' (as all optional/array elements must be 'parsed') (2) Missing restriction - for 'stopValue' the dfdl:stopValue property must not include empty string. (3) maxOccurs provides count, so nothing is eligible for suppression, so SSP has no practical effect (same as a required element) (4) infoset provides count, so nothing is eligible for suppression, so SSP has no practical effect (same as a required element) (5) 'parsed' only makes sense with 'anyEmpty' (6) Because a stop value must appear, and from (2) empty string is not allowed, SSP has no practical effect. The issue of maxOccurs = '0' is discussed in a separate email. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 13/10/2014 14:40 ----- From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Steve Hanson/UK/IBM@IBMGB, Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 29/08/2014 21:21 Subject: Re: [DFDL-WG] Fw: Action 260 I reviewed this. It looks good to me. The note at the bottom that we don't say what happens on a zero-trip I.e., a represented element, but where occursCount evaluates to 0, is a useful clarification also. Do we want to create an erratum for this? Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Thu, Aug 28, 2014 at 10:13 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: Please review for Tuesday's WG call ... Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 28/08/2014 15:02 ----- From: Steve Hanson/UK/IBM To: dfdl-wg(a)ogf.org, Date: 06/08/2014 13:50 Subject: Fw: [DFDL-WG] Action 260 So my suggestion below, to wrap the array in a sequence, does not work; it just moves the problem down into the new sequence. After much deliberation, we think that the definitions of Positional sequence and Non-positional sequence should not be viewed as driving the behaviour of a sequence, but simply as the resultant characteristics of a sequence that has certain properties. That leaves modellers free to mix occursCountKinds, as in Tim's example. No need for any new SDE scenarios. Positional sequence - Each occurrence in the sequence can be identified by its position in the data. Typically the components of such a sequence do not have an initiator. In some such sequences, the separators for optional zero-length occurrences may or must be omitted when at the end of the group. In DFDL, a sequence is considered positional if it contains only required elements and/or optional and array elements that have dfdl:occursCountKind 'implicit', 'fixed' or 'expression', and it has dfdl:separatorSuppressionPolicy 'never', 'trailingEmptyStrict' or 'trailingEmpty'. Non-positional sequence - Occurrences in the sequence cannot be identified by their position in the data alone. Often the components of such a sequence have an initiator. Such sequences sometimes allow the separator to be omitted for optional zero-length occurrences anywhere in the sequence. Speculative parsing might need to be employed by to identify each occurrence. In DFDL, a sequence is non-positional if it contains any optional or array elements that have dfdl:occursCountKind 'parsed' or 'stopValue', and/or it has dfdl:separatorSuppressionPolicy 'anyEmpty'. See parallel email for action 261 that ensures 'expression' behaves itself. One behaviour that is missing from the spec. For a sequence with separators, what is expected in the data stream if occursCount = 'fixed' / 'implicit' and maxOccurs = '0', or occursCountKind = 'expression' and occursCount evaluates to 0 ? We believe that no separator should be expected when parsing and none output when unparsing (same behaviour as inputValueCalc). Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 ----- Forwarded by Steve Hanson/UK/IBM on 06/08/2014 12:42 ----- From: Steve Hanson/UK/IBM To: Tim Kimber/UK/IBM@IBMGB, Cc: dfdl-wg(a)ogf.org, dfdl-wg-bounces(a)ogf.org Date: 30/06/2014 10:04 Subject: Re: [DFDL-WG] Action 260 You would wrap the array and it's count in a sequence. Then the 'count+array' is treated as a single entity as far as the parent sequence is concerned. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 From: Tim Kimber/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org, Date: 26/06/2014 20:06 Subject: Re: [DFDL-WG] Action 260 Sent by: dfdl-wg-bounces(a)ogf.org Before we settle one way or the other, I would like the following data format to be taken into consideration. chars,5,A,B,C,D,E,integers,1,2,3 chars,3,C,,,integers,2,10,11 I am assuming that the occursCountKind for the arrays is 'expression' and the occursCount refers to the integer field that precedes the array. In order to represent the empty strings on the second line it is essential to specify SSP as 'trailingEmpty' or 'never'. If we disallow the combination of ock='expression' and SSP='trailingEmpty' then how would this format be modelled? regards, Tim Kimber, Technical Lead for IBM Integration Bus Healthcare Pack Hursley, UK Internet: kimbert(a)uk.ibm.com Tel. 01962-816742 Internal tel. 37246742 From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Steve Hanson/UK/IBM@IBMGB, Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 25/06/2014 16:25 Subject: Re: [DFDL-WG] Action 260 Sent by: dfdl-wg-bounces(a)ogf.org I prefer choice (a) for two reasons * It is more restrictive and therefore more conservative (preserving freedom to change in future if needed) * If a user has a positional data format, you don't want them to even have to understand the concept of speculation in order to model their data. So choice (a) allows a simpler description that doesn't need to introduce the notion that the parser might be speculation. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Wed, Jun 25, 2014 at 5:20 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: 260 Positional and non-positional sequences (All) 10/6: Spec defines the above but also allows different occursCountKinds within the same sequence which may have different (implied) separatorSuppressionPolicy, which results in a sequence which is a mixture of both. Should this be allowed? If so what are the rules? Can certain combinations be disallowed? 17/6: IBM have discussed internally and will submit a proposal. In the spec we define Positional Sequence and Non-Positional Sequence: Positional sequence - Each occurrence in the sequence can be identified by its position in the data. Typically the components of such a sequence do not have an initiator. In some such sequences, the separators for optional zero-length occurrences may or must be omitted when at the end of the group. A positional sequence can be modelled by setting dfdl:separatorSuppressionPolicy to 'never', 'trailingEmptyStrict' or 'trailingEmpty'. Non-positional sequence - Occurrences in the sequence cannot be identified by their position in the data alone. Typically the components of such a sequence have an initiator. Such sequences allow the separator to be omitted for optional zero-length occurrences anywhere in the sequence. Speculative parsing is employed by the parser to identify each occurrence. A non-positional sequence can be modelled by setting dfdl:separatorSuppressionPolicy to 'anyEmpty'. The problem is that the setting of dfdl:separatorSuppressionPolicy is only examined for child elements with dfdl:occursCountKind 'implicit'. For other dfdl:occursCountKinds, there is the concept of an 'implied' dfdl:separatorSuppressionPolicy: When dfdl:occursCountKind is 'fixed' then ... the implied behaviour is 'never'. When dfdl:occursCountKind is 'expression' ... the implied behaviour is 'never'. When dfdl:occursCountKind is 'parsed' ... the implied behaviour is 'anyEmpty'. When dfdl:occursCountKind is 'stopValue' ...the implied behaviour is 'anyEmpty'. So if a Positional sequence as defined above contains children with dfdl:occursCountKind 'parsed' or 'stopValue' then surely it is no longer a Positional sequence. A solution to this is to prevent the appearance of certain values of dfdl:occursCountKind within a Positional sequence. However, precisely which values to outlaw is subject to interpretation of the phrase "Each occurrence in the sequence can be identified by its position in the data". Is this intended to mean: a) an observer of the raw data can identify an occurrence of an element in the sequence solely by counting separators => SDE if 'parsed', 'stopValue' or 'expression' ** appeared in a Positional sequence; ** Although 'expression' would appear to be like 'fixed' it actually breaks a) so must be included in the SDE list. or b) a parser does not have to speculate to identify an occurrence of an element in the sequence => SDE only if 'parsed' appeared in a Positional sequence. Note that it is possible to wrap a 'parsed' etc element in a local sequence or another element to avoid an SDE. But this could still be seen as a violation of a) if the separators of both are the same, as the observer can not count the separators. So should the rule be applied recursively, ie, a Positional sequence can not contain a non-Positional sequence unless the separators are different? Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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 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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 -- dfdl-wg mailing list dfdl-wg(a)ogf.org https://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 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 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

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Action 271: semantic of maxoccurs '0'
by Steve Hanson 25 Nov '14

25 Nov '14

271 Use of maxOccurs '0' (All) 2/9: Legal in XSDL and DFDL. One use case in XSDL is when deriving a complex type by restriction, where it is used to indicate that an element in the base type must not appear. Another use case could be if a schema undergoes a version revision that removes elements; perhaps clearer if the removed element gets maxOccurs '0' rather than omitting it. Steve has seen an instance of its use in a DFDL schema. So if DFDL continues to support it, need to document the behaviour for the various occursCountKinds and what happens to separator. Also behaviour of occursCount expression that returns 0. Proposal needed. ... 23/9: No progress IBM has discussed this internally and has the following proposal. Infoset refers to the augmented infoset. OCK maxOccurs '0' Parsing Unparsing fixed No occurrences looked for in the data (1) No occurrences looked for in the infoset or written (2) implicit No occurrences looked for in the data (1) No occurrences looked for in the infoset or written (2) expression occursCount occurrences expected. If any are found it is a validation error. Any number of occurrences expected in the infoset and written. If any are found it is a validation error. parsed Any number of occurrences expected in the data. If any are found it is a validation error. Any number of occurrences expected in the infoset and written. If any are found it is a validation error. stopValue Any number of occurrences expected in the data. If any are found it is a validation error. Any number of occurrences expected in the infoset and written. If any are found it is a validation error. OCK Parsing and occursCount '0' Unparsing and no occurrences in infoset expression No occurrences looked for in the data. (1) No occurrences written. (2) Notes (1) If sequence has a separator, no separator is looked for in the data when parsing. (2) If sequence has a separator, no separator is output when unparsing. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848 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

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OGF DFDL WG Call Agenda 2014-11-25
by Steve Hanson 24 Nov '14

24 Nov '14

Please find agenda for call on Redmine at http://redmine.ogf.org/dmsf_files/13377?download= Regards Steve Hanson Architect, IBM Data Format Description Language (DFDL) Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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dfdl github - mil-std-2045 schema updated
by Mike Beckerle 19 Nov '14

19 Nov '14

I finally got around to enhancing the mil-std-2045 schema using the ideas that came out of review of the original work. It is vastly improved in terms of complexity of the schema, and other schemas that have to generate this sort of thing are greatly simplified by the techniques illustrated here which avoid the need to generate any top-level group definitions. I did have to put in the workaround of using "WSP*" in a terminator instead of "ES" because Daffodil doesn't support ES in terminators yet (there's a bug). I also left out the defaults, which are needed for unparsing, due to a bug in Daffodil. https://github.com/DFDLSchemas/mil-std-2045 Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php>

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OGF DFDL WG Call Minutes 2014-11-18
by Steve Hanson 19 Nov '14

19 Nov '14

Please find minutes from the above call at http://redmine.ogf.org/dmsf_files/13374?download= ** Updated DFDL 1.0 specification published at http://www.ogf.org/documents/GFD.207.pdf. ** Regards Steve Hanson Architect, IBM DFDL, Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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