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Re: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....)
by Steve Hanson 25 Aug '15

25 Aug '15

My thoughts on this... The existing choice branch rule that says minOccurs must not be 0 should remain, for consistency with not allowing minOccurs 0 on the choice itself. Choice branch with dfdl:occursCountKind 'expression' should be allowed. If the expression resolves to 0 then there are no occurrences and the branch is missing, so the parser looks for the next branch. This preserves the rule that a branch must exist. Choice branch with dfdl:occursCountKind 'parsed' should be allowed. If the parser does not find any occurrences then the branch is missing, so the parser looks for the next branch. This preserves the rule that a branch must exist. dfdl;inputValueCalc on a choice branch should be allowed. If the parser reaches such a branch, it discriminates the choice and no further branches are examined. 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: 11/08/2015 15:58 Subject: Re: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....) I may have thought of the reason. If I have a choice of A and B, then minOccurs=0 for B allows the choice to be empty A|B? but this is the same as (A|B)? which is allowing the choice itself to be minOccurs=0, which is not allowed. 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: 18/06/2015 10:49 Subject: Re: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....) Hi Mike I think the restriction of having minOccurs >= 1 on xs:choice branch arose for two reasons, though I am unable to find a definitive email trail: a) If minOccurs = 0 you immediately have two points of uncertainty, so potentially two discriminators are needed. I'm not sure if this is really a problem though, because if minOccurs < maxOccurs there are also two points of uncertainty and it still requires some thought to get discrimination correct as it varies per occurrence. b) Interaction with known-to-exist rules. For example, one way to achieve known-to-exist is to successfully parse an empty representation, which with minOccurs = 0 may mean that nothing is added to the infoset. I'm not sure this is actually a problem though. If the branch was successfully parsed then surely that should discriminate in favour of the branch regardless of representation. And even if a) and b) are problematic, the fact exists that you can trivially negate the restriction by wrapping in xs:sequence. So I suspect we can drop the restriction altogether, and the 'system' just works in a consistent manner. You raised the issue of an element with dfdl:inputValueCalc not being allowed as a choice branch. I suspect this was added because as soon as you encounter such as branch you have by definition discriminated in favour of that branch. But that's ok, you just make that branch the last in the choice. No different to having a branch that exists just to throw an error - it too must be last. If such branches are not last, it's a schema design bug. Back to Alex's original scenario at the foot of this thread, where his xs:choice branch element had a dfdl:occursCount expression that evaluated to 0. According to https://redmine.ogf.org/issues/244 no occurrences are looked for in the data. That means the occurrences are missing, so known-not-to-exist and the parser should try the next branch. Below I said that section 15.1.1 needed updating to correctly reflect section 9. And I also said we are perhaps missing a definition of what 'missing' means for an array element? "(The) spec defines known-to-exist and known-not-to-exist in terms of occurrences. In (Alex's) choice branch example, it is the element as a whole we are looking at. That's fine for scalar as element == occurrence but for an array it's not the same. I think the spec is missing a definition of what 'missing' means for an array element. I would say that an array element is missing if all occurrences are missing. And an array element is not missing if any occurrence has a representation (empty, nil, normal)." 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: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 02/06/2015 18:41 Subject: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....) Sent by: dfdl-wg-bounces(a)ogf.org I believe this action item remains open still and I would like to revive the discussion. I was coding up this aspect of Daffodil and have hit this subject head on. In section 15 the spec clearly states that the root of a choice branch cannot be optional, that is cannot have minOccurs="0". That language is very specific, and it leaves open the possibility of "effectively optional" things being the roots of choice branches (e.g., using OCK 'parsed' or 'expression') It also allows one to trivially wrap a sequence (having no delimiters, alignment or skips) around an element (or element ref) carrying minOccurs="0" so as to simply dodge the restriction. It was observed in the thread below that we cannot require choice branches to be scalar elements as there is a need for hidden groups to be branches of choices, and for empty sequences carrying only asserts, as another non-element example. Related: the DFDL spec also specifies that an element that is the root of a choice branch cannot carry dfdl:inputValueCalc. The spec does NOT restrict use of dfdl:outputValueCalc on the root of a choice branch, but the meaning of such is unclear to me. The existing restriction of "no minOccurs="0" on the root of a choice branch seems not to accomplish anything. It is only for occursCountKind='implicit' where this can be meaningful it seems. Requiring the root of a choice branch to not be "variable occurrence" if it is an element would accomplish something, but it is not clear this is needed to eliminate ambiguity or if the ambiguity can be eliminated without any restriction. The stable design points I can think of are: 1) root of a choice branch must be scalar (so, only a sequence, choice, or an element where minOccurs == maxOccurs == 1.) 2) root of a choice branch cannot be optional - for a broad sense of the word optional - precludes arrays with OCK expression and parsed, and implicit if minOccurs="0". Fixed length arrays would be allowed. 3) a choice branch must have some syntax I think we discarded (3) because choice branches that really just reflect error checking - contain only dfdl:asserts for example - are in use and serve a useful purpose. Daffodil's test suite has much use of choice branches that look like this: <choicie> ..... <sequence> <element name="foo" dfdl:inputValueCalc="{....}"/> </sequence> </choice> These have no syntax. This allowing a kind of default-element to be computed. In most (could be all, I've not searched exhaustively) of these cases the IVC expression is a constant. But note that the sequence wrapped around the IVC element is just dodging the restriction that a choice branch cannot be an IVC element (which is another restriction that seems unnecessary.) ...mike 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, Apr 27, 2015 at 9:30 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: Mike A couple of comments: 1) You said below Optional here means "not required by the DFDL format", as in occursCountKind cannot be 'parsed' at all, because all occurrences are then not required, and the min/maxOccurs are only examined for validation purposes, also occursCountKind cannot be 'implicit' for the same reasons, and occursCountKind 'expression' also. OccursCountKind 'implicit' is allowed, because minOccurs is used for parsing and micOccurs can not be 0. 2) You said below Wrapping the array element in a sequence doesn't solve the problem unless the sequence has a required piece of syntax such as an initiator or terminator, or a hiddenGroupRef to a not-optional (recursively) thing. A sequence has minOccurs '1' so it does satisfy the spec rule about the child of a choice being required. Such a sequence could have no syntax and could contain an element with minOccurs '0' or even be empty. I have seen DFDL schemas that contain a choice with the last branch being an empty sequence that contains an assert fn:false() in order to throw a processing 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 From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Alex Wood1/UK/IBM@IBMGB Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 27/04/2015 13:35 Subject: Re: [DFDL-WG] OCK expression and count of 0 for a choice member.... Sent by: dfdl-wg-bounces(a)ogf.org I believe any use of occursCountKind 'expression' on an element that is the first element on a branch of a choice should be an SDE. This is one of the cases where DFDL requires one to introduce an element that would not be necessary in an ordinary XML schema, but is necessary because DFDL does not have XML's easily parsed syntax to depend on. This is my opinion. I think we need to look at whether this restriction is either (a) necessary (b) necessary to avoid excessive complexity in implementations (c) unnecessary - but is the intention of what is specified already (despite shortcomings of the prose/description in the spec, which could be corrected.) (d) an error in the specification 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, Apr 27, 2015 at 5:49 AM, Alex Wood1 <WOODA(a)uk.ibm.com> wrote: Hi Mike, Can you clarify if you are saying that OCK expression should be prohibited completely on a choice member (as occurrences for OCK expression are potentially optional regardless of minOccurs value) Or is your statement that it should cause an SDE specific to the count==0 case? Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Alex Wood1/UK/IBM@IBMGB Date: 24/04/2015 15:10 Subject: Re: [DFDL-WG] OCK expression and count of 0 for a choice member.... I think this is an SDE. Choice branches cannot be optional. Optional here, does not mean minOccurs == 0, because for many occursCountKinds, that's never checked unless validation is on, and validation doesn't guide parsing anyway. Optional here means "not required by the DFDL format", as in occursCountKind cannot be 'parsed' at all, because all occurrences are then not required, and the min/maxOccurs are only examined for validation purposes, also occursCountKind cannot be 'implicit' for the same reasons, and occursCountKind 'expression' also. Wrapping the array element in a sequence doesn't solve the problem unless the sequence has a required piece of syntax such as an initiator or terminator, or a hiddenGroupRef to a not-optional (recursively) thing. Even initiator and terminator are tricky, because in a non-delimited format, those can be %WSP*; which can match nothing at all; hence, they do not "require" any syntax. 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 Fri, Apr 24, 2015 at 9:07 AM, Alex Wood1 <WOODA(a)uk.ibm.com> wrote: Hi All, Please see below for a history of the issue. This arose from fuzz testing of the IBM DFDL parser which produced a test with a coutn of 0 for an OCK expression array which was a choice member. And subsequent reference to the specification. It was not clear what the correct outcome should be in a choice where the first member is an array using OCK expression where the count resolves to 0. a.) resolve the choice to the zero length array b.) move to the next choice branch c.) throw an error Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com From: Steve Hanson/UK/IBM To: Alex Wood1/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM Date: 24/04/2015 09:19 Subject: Re: OCK expression and count of 0 for a choice member.... When I wrote the paragraph below, the one thing that troubled me was that the spec defines known-to-exist and known-not-to-exist in terms of occurrences. In the choice branch example, it is the element as a whole we are looking at. That's fine for scalar as element == occurrence but for an array it's not the same. I think the spec is missing a definition of what 'missing' means for an array element. I would say that an array element is missing if all occurrences are missing. And an array element is not missing if any occurrence has a representation (empty, nil, normal). With that in place, my paragraph makes sense, I think. I believe we have the same issue with 'parsed' and 'stopValue'. 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: Alex Wood1/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM@IBMGB Date: 23/04/2015 18:52 Subject: Re: OCK expression and count of 0 for a choice member.... Here is one interpretation... A choice is resolved by parsing the branches until one is known-to-exist as described in section 9.3.3. Section 9.3.1.2 defines known-to-exist (in the absence of a discriminator, initiator or direct dispatch) as an occurrence having empty, nil or normal representation. Section 9.3.1.3 defines known-not-to-exist (again in the absence of a discriminator, initiator or direct dispatchm or an assert) as an occurrence being missing or causing a processing error. If occursCount is zero no occurrences are looked for in the data (erratum 5.9) so the element has no representation and must be missing. Therefore a choice branch containing such an element is known-not-to-exist. So in your example, the first choice branch containing myInt is known-not-to-exist and the parser tries the next branch. This appears to contradict section 15.1.1 though. I suspect that 15.1.1 was not updated to match section 9.3 when the latter was added. If you want to make the first choice branch known-to-exist when the count is zero then I think wrapping myInt in a sequence would work. Or wrapping myInt in a complex element. Definitely one to take to the WG though, if only to correct section 15.1.1 to match section 9. 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: Alex Wood1/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM@IBMGB Date: 23/04/2015 16:33 Subject: OCK expression and count of 0 for a choice member.... Hi Steve Just been discussing this with Andy and Mark. I think the spec <xs:element name="Choice_Expression" dfdl:ref="config" dfdl:lengthKind="implicit"> <xs:complexType> <xs:sequence dfdl:ref="config"> <xs:element ref="myCount"></xs:element> <xs:choice dfdl:choiceLengthKind="implicit" dfdl:ref="config"> <xs:element ref="myInt" minOccurs="1" maxOccurs="3"></xs:element> <xs:element ref="myTxt"></xs:element> </xs:choice> </xs:sequence> </xs:complexType> </xs:element> Where myInt has occursCountKind="expression" occursCount="{../myCount}" A given instance of this message could have myCount==0 Is this valid? Should it resolve to 0 occurrences of myInt or move on to myTxt ? Section15 of the spec says: The Root of the Branch MUST NOT be optional. That is XSDL minOccurs MUST BE greater than 0. But in this case minOccurs is >0. Assuming this is not an error then in terms of resolving the choice section 15.1.1 says.. 15.1.1 Resolving Choices via Speculation Speculative resolution works as follows: 1) Attempt to parse the first branch of the choice. 2) If this fails with a processing error a) If a dfdl:discriminator evaluated to true earlier on this branch then the parser is 'bound' to this branch and parsing of the entire choice construct fails with a processing error. b) If the branch has a dfdl:initiator and the choice has dfdl:initiatedContent ‘yes’ then the parser is 'bound' to this branch and parsing of the entire choice construct fails with a processing error. c) Otherwise we repeat from step 1 for the next branch of the choice. 3) It is a processing error if the branches of the choice are exhausted. 4) If a branch is successfully parsed without error, then that branch's infoset becomes the infoset for the parse of the choice construct. So seems like this is 4.) we did not fail to parse myInt... However talking with mark about real scenarios that this might apply to, a choice two repeating fields with counts earlier in the data only one of which must appear. you'd expect 0 of the first means >0 of the second and visa versa... So you'd probably want 0 myInt allowed the choice to resolve to myTxt. Thoughts ? If you agree we need more clarity in he spec will forward to WG. Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com 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 -- 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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OGF DFDL WG Call Minutes 2015-08-11
by Steve Hanson 12 Aug '15

12 Aug '15

Please find minutes from the above call at https://redmine.ogf.org/dmsf_files/13489?download= Next call is 25th August. 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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Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol
by Steve Hanson 12 Aug '15

12 Aug '15

Andy - yes that is the behaviour I am seeing. 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: Andrew Edwards/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 11/08/2015 17:28 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol Following on from today's call, the relevant piece of documentation is in http://icu-project.org/apiref/icu4c/classicu_1_1SimpleDateFormat.html When numeric fields abut one another directly, with no intervening delimiter characters, they constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible, while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost field is shortened by one character, and the entire run is parsed again. This is repeated until either the parse succeeds or the leftmost field is one character in length. If the parse still fails at that point, the parse of the run fails. So it seems that when the 'S' is next to other numeric units in the pattern, it will be subject to the above behaviour. Therefore: - A pattern of HHmmssSSS with the input 112233123 will become 11:22:33.123 but the input 1122331234 will trigger an error. - If the pattern includes a '.' to become HHmmss.SSS, I think the input 1122331234 will become 11:22:33.123 but I'll try and confirm. Steve - Does that description match what you were seeing? HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards(a)uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times From: Steve Hanson/UK/IBM To: Andrew Edwards/UK/IBM@IBMGB Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 11/08/2015 12:53 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol Hi Andy Your internal ticket #630 gave rise to external ticket http://bugs.icu-project.org/trac/ticket/10962, which claims to have fixed the API docs to clarify the behaviour. S fractional second - truncates (like other time fields) to the count of letters when formatting. Appends zeros if more than 3 letters specified. Truncates at three significant digits when parsing. S SS SSS SSSS 2 23 235 2350 I can't see anywhere that addresses your point about about abutting versus non-abutting numeric symbols though? As far as DFDL spec is concerned, this is what we say today: S fractional second (see note 1) Number S SS SSS 2 24 235 There is no 'note 1', I think the note was made into a normal paragraph, which reads: Any number of fractional seconds "S" may by specified in the pattern and accepted by implementations, but an implementation is free to represent a limited number of fractional seconds internally. Excess fractional seconds are truncated, not rounded up. At least millisecond accuracy must be implemented. Unlike other fields, fractional seconds are padded on the right with zero. 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: Andrew Edwards/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Date: 11/08/2015 11:56 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Hi Steve Re agenda item 2 and calendar patterns with 'S', this ICU ticket from last year might be relevant - https://icu.sanjose.ibm.com/gcoctrac/ticket/630. It seems that the error reporting may also depend on whether the pattern has 'S' on it's own or next to other numeric pattern entities. i.e. 'HHmmssS' is subject to length checking, but 'HHmmss S' is not, due to the space before the 'S'. HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards(a)uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times From: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Cc: Mike Beckerle <mbeckerle(a)tresys.com>, jorge.marizan(a)gmail.com Date: 10/08/2015 18:29 Subject: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Sent by: dfdl-wg-bounces(a)ogf.org Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13489?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 -- 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] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol
by Andrew Edwards 11 Aug '15

11 Aug '15

Following on from today's call, the relevant piece of documentation is in http://icu-project.org/apiref/icu4c/classicu_1_1SimpleDateFormat.html When numeric fields abut one another directly, with no intervening delimiter characters, they constitute a run of abutting numeric fields. Such runs are parsed specially. For example, the format "HHmmss" parses the input text "123456" to 12:34:56, parses the input text "12345" to 1:23:45, and fails to parse "1234". In other words, the leftmost field of the run is flexible, while the others keep a fixed width. If the parse fails anywhere in the run, then the leftmost field is shortened by one character, and the entire run is parsed again. This is repeated until either the parse succeeds or the leftmost field is one character in length. If the parse still fails at that point, the parse of the run fails. So it seems that when the 'S' is next to other numeric units in the pattern, it will be subject to the above behaviour. Therefore: - A pattern of HHmmssSSS with the input 112233123 will become 11:22:33.123 but the input 1122331234 will trigger an error. - If the pattern includes a '.' to become HHmmss.SSS, I think the input 1122331234 will become 11:22:33.123 but I'll try and confirm. Steve - Does that description match what you were seeing? HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards(a)uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times From: Steve Hanson/UK/IBM To: Andrew Edwards/UK/IBM@IBMGB Cc: DFDL-WG <dfdl-wg(a)ogf.org> Date: 11/08/2015 12:53 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol Hi Andy Your internal ticket #630 gave rise to external ticket http://bugs.icu-project.org/trac/ticket/10962, which claims to have fixed the API docs to clarify the behaviour. S fractional second - truncates (like other time fields) to the count of letters when formatting. Appends zeros if more than 3 letters specified. Truncates at three significant digits when parsing. S SS SSS SSSS 2 23 235 2350 I can't see anywhere that addresses your point about about abutting versus non-abutting numeric symbols though? As far as DFDL spec is concerned, this is what we say today: S fractional second (see note 1) Number S SS SSS 2 24 235 There is no 'note 1', I think the note was made into a normal paragraph, which reads: Any number of fractional seconds "S" may by specified in the pattern and accepted by implementations, but an implementation is free to represent a limited number of fractional seconds internally. Excess fractional seconds are truncated, not rounded up. At least millisecond accuracy must be implemented. Unlike other fields, fractional seconds are padded on the right with zero. 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: Andrew Edwards/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Date: 11/08/2015 11:56 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Hi Steve Re agenda item 2 and calendar patterns with 'S', this ICU ticket from last year might be relevant - https://icu.sanjose.ibm.com/gcoctrac/ticket/630. It seems that the error reporting may also depend on whether the pattern has 'S' on it's own or next to other numeric pattern entities. i.e. 'HHmmssS' is subject to length checking, but 'HHmmss S' is not, due to the space before the 'S'. HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards(a)uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times From: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Cc: Mike Beckerle <mbeckerle(a)tresys.com>, jorge.marizan(a)gmail.com Date: 10/08/2015 18:29 Subject: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Sent by: dfdl-wg-bounces(a)ogf.org Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13489?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 -- 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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Fw: [DFDL]: First Release of DFDL4S Parser Library
by Steve Hanson 11 Aug '15

11 Aug '15

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 11/08/2015 16:27 ----- From: Michele Zundo <michele.zundo(a)esa.int> To: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> Cc: Steve Hanson/UK/IBM@IBMGB, Maurizio De Bartolomei <Maurizio.De.Bartolomei(a)esa.int>, Montserrat Piñol <mpinol(a)eopp.esa.int>, "Rui Mestre (DME)" <rui.mestre(a)deimos.com.pt> Date: 18/05/2015 08:47 Subject: Re: [DFDL]: First Release of DFDL4S Parser Library Thanks Mike, we will add this to our list to be considered/noted. However reading your explanation (NB I’m NOT at all an XPath expert) it seemed you had some good reason for avoiding longer than 1 path, so I would like to avoid our DFDL4S project results in an over-complication of the DFDL implementation/use of Xpath unless there are other reasons/users/rationale requiring this feature. (btw the syntax is still weird-ish: “intersect” reminds me of Venn Diagrams…) As a project manager I always evaluate solutions and their cost vs the benefit they bring, and I believe the DFDL community should keep this is mind. Michele PS The syntax above anser to the question “belongs to” , would there be any way to express ranges of values then ? On 15 May 2015, at 16:24 , Mike Beckerle <mbeckerle.dfdl(a)gmail.com> wrote: Just a few comments on DFDL4S, and also thank you to Michele and team for the presentation on Tuesday. I think all the issues in the spreadsheet are fairly easily fixed in that they are not major changes to DFDL4S, and would bring it into much closer compliance with the DFDL spec. The exception is the XPath limitations where DFDL4S has gone beyond what XPath 2.0 allows and invented new syntax for expressing set membership requirements. So I took a look, and XPath 2.0 has a set intersect operator: ns1 intersect ns2 => ns3 This isn't in DFDL today, but might be usable to achieve the set membership test; however, it requires use of XPath node sequences of length greater than 1, which DFDL has avoided mostly. I say mostly as there are XPath expressions that return node sequences of length greater than 1 and those can be arguments to fn:count(...) for example. So far in DFDL such node sequences cannot "leak out" of the XPath expression into DFDL elements, and I think the usage in DFDL4S is similar in that these node sequences would be needed only to check for set membership, so the result is just a boolean as part of an assert/discriminator. We should examine whether XPath 2.0 set intersection is enough to meet the need. I believe the expressions would be something like: fn:exists( . intersect (123, 456, 789, .... many more items....) ) - mike beckerle 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, May 12, 2015 at 10:45 AM, Michele Zundo <michele.zundo(a)esa.int> wrote: for reference, here a summary of the reported problem in an excel sheet. This message and any attachments are intended for the use of the addressee or addressees only. The unauthorised disclosure, use, dissemination or copying (either in whole or in part) of its content is not permitted. If you received this message in error, please notify the sender and delete it from your system. Emails can be altered and their integrity cannot be guaranteed by the sender. Please consider the environment before printing this email. ----------------------------------------- Michele Zundo Head of Ground System Definition and Verification Office EOP-PEP European Space Agency, ESTEC e-mail: michele.zundo(a)esa.int ----------------------------------------- Michele Zundo Head of Ground System Definition and Verification Office EOP-PEP European Space Agency, ESTEC e-mail: michele.zundo(a)esa.int This message and any attachments are intended for the use of the addressee or addressees only. The unauthorised disclosure, use, dissemination or copying (either in whole or in part) of its content is not permitted. If you received this message in error, please notify the sender and delete it from your system. Emails can be altered and their integrity cannot be guaranteed by the sender. Please consider the environment before printing this email. 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] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....)
by Steve Hanson 11 Aug '15

11 Aug '15

I may have thought of the reason. If I have a choice of A and B, then minOccurs=0 for B allows the choice to be empty A|B? but this is the same as (A|B)? which is allowing the choice itself to be minOccurs=0, which is not allowed. 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: 18/06/2015 10:49 Subject: Re: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....) Hi Mike I think the restriction of having minOccurs >= 1 on xs:choice branch arose for two reasons, though I am unable to find a definitive email trail: a) If minOccurs = 0 you immediately have two points of uncertainty, so potentially two discriminators are needed. I'm not sure if this is really a problem though, because if minOccurs < maxOccurs there are also two points of uncertainty and it still requires some thought to get discrimination correct as it varies per occurrence. b) Interaction with known-to-exist rules. For example, one way to achieve known-to-exist is to successfully parse an empty representation, which with minOccurs = 0 may mean that nothing is added to the infoset. I'm not sure this is actually a problem though. If the branch was successfully parsed then surely that should discriminate in favour of the branch regardless of representation. And even if a) and b) are problematic, the fact exists that you can trivially negate the restriction by wrapping in xs:sequence. So I suspect we can drop the restriction altogether, and the 'system' just works in a consistent manner. You raised the issue of an element with dfdl:inputValueCalc not being allowed as a choice branch. I suspect this was added because as soon as you encounter such as branch you have by definition discriminated in favour of that branch. But that's ok, you just make that branch the last in the choice. No different to having a branch that exists just to throw an error - it too must be last. If such branches are not last, it's a schema design bug. Back to Alex's original scenario at the foot of this thread, where his xs:choice branch element had a dfdl:occursCount expression that evaluated to 0. According to https://redmine.ogf.org/issues/244 no occurrences are looked for in the data. That means the occurrences are missing, so known-not-to-exist and the parser should try the next branch. Below I said that section 15.1.1 needed updating to correctly reflect section 9. And I also said we are perhaps missing a definition of what 'missing' means for an array element? "(The) spec defines known-to-exist and known-not-to-exist in terms of occurrences. In (Alex's) choice branch example, it is the element as a whole we are looking at. That's fine for scalar as element == occurrence but for an array it's not the same. I think the spec is missing a definition of what 'missing' means for an array element. I would say that an array element is missing if all occurrences are missing. And an array element is not missing if any occurrence has a representation (empty, nil, normal)." 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: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 02/06/2015 18:41 Subject: [DFDL-WG] Action 280 minOccurs='0' choice branch (was: Re: OCK expression and count of 0 for a choice member....) Sent by: dfdl-wg-bounces(a)ogf.org I believe this action item remains open still and I would like to revive the discussion. I was coding up this aspect of Daffodil and have hit this subject head on. In section 15 the spec clearly states that the root of a choice branch cannot be optional, that is cannot have minOccurs="0". That language is very specific, and it leaves open the possibility of "effectively optional" things being the roots of choice branches (e.g., using OCK 'parsed' or 'expression') It also allows one to trivially wrap a sequence (having no delimiters, alignment or skips) around an element (or element ref) carrying minOccurs="0" so as to simply dodge the restriction. It was observed in the thread below that we cannot require choice branches to be scalar elements as there is a need for hidden groups to be branches of choices, and for empty sequences carrying only asserts, as another non-element example. Related: the DFDL spec also specifies that an element that is the root of a choice branch cannot carry dfdl:inputValueCalc. The spec does NOT restrict use of dfdl:outputValueCalc on the root of a choice branch, but the meaning of such is unclear to me. The existing restriction of "no minOccurs="0" on the root of a choice branch seems not to accomplish anything. It is only for occursCountKind='implicit' where this can be meaningful it seems. Requiring the root of a choice branch to not be "variable occurrence" if it is an element would accomplish something, but it is not clear this is needed to eliminate ambiguity or if the ambiguity can be eliminated without any restriction. The stable design points I can think of are: 1) root of a choice branch must be scalar (so, only a sequence, choice, or an element where minOccurs == maxOccurs == 1.) 2) root of a choice branch cannot be optional - for a broad sense of the word optional - precludes arrays with OCK expression and parsed, and implicit if minOccurs="0". Fixed length arrays would be allowed. 3) a choice branch must have some syntax I think we discarded (3) because choice branches that really just reflect error checking - contain only dfdl:asserts for example - are in use and serve a useful purpose. Daffodil's test suite has much use of choice branches that look like this: <choicie> ..... <sequence> <element name="foo" dfdl:inputValueCalc="{....}"/> </sequence> </choice> These have no syntax. This allowing a kind of default-element to be computed. In most (could be all, I've not searched exhaustively) of these cases the IVC expression is a constant. But note that the sequence wrapped around the IVC element is just dodging the restriction that a choice branch cannot be an IVC element (which is another restriction that seems unnecessary.) ...mike 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, Apr 27, 2015 at 9:30 AM, Steve Hanson <smh(a)uk.ibm.com> wrote: Mike A couple of comments: 1) You said below Optional here means "not required by the DFDL format", as in occursCountKind cannot be 'parsed' at all, because all occurrences are then not required, and the min/maxOccurs are only examined for validation purposes, also occursCountKind cannot be 'implicit' for the same reasons, and occursCountKind 'expression' also. OccursCountKind 'implicit' is allowed, because minOccurs is used for parsing and micOccurs can not be 0. 2) You said below Wrapping the array element in a sequence doesn't solve the problem unless the sequence has a required piece of syntax such as an initiator or terminator, or a hiddenGroupRef to a not-optional (recursively) thing. A sequence has minOccurs '1' so it does satisfy the spec rule about the child of a choice being required. Such a sequence could have no syntax and could contain an element with minOccurs '0' or even be empty. I have seen DFDL schemas that contain a choice with the last branch being an empty sequence that contains an assert fn:false() in order to throw a processing 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 From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Alex Wood1/UK/IBM@IBMGB Cc: "dfdl-wg(a)ogf.org" <dfdl-wg(a)ogf.org> Date: 27/04/2015 13:35 Subject: Re: [DFDL-WG] OCK expression and count of 0 for a choice member.... Sent by: dfdl-wg-bounces(a)ogf.org I believe any use of occursCountKind 'expression' on an element that is the first element on a branch of a choice should be an SDE. This is one of the cases where DFDL requires one to introduce an element that would not be necessary in an ordinary XML schema, but is necessary because DFDL does not have XML's easily parsed syntax to depend on. This is my opinion. I think we need to look at whether this restriction is either (a) necessary (b) necessary to avoid excessive complexity in implementations (c) unnecessary - but is the intention of what is specified already (despite shortcomings of the prose/description in the spec, which could be corrected.) (d) an error in the specification 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, Apr 27, 2015 at 5:49 AM, Alex Wood1 <WOODA(a)uk.ibm.com> wrote: Hi Mike, Can you clarify if you are saying that OCK expression should be prohibited completely on a choice member (as occurrences for OCK expression are potentially optional regardless of minOccurs value) Or is your statement that it should cause an SDE specific to the count==0 case? Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com From: Mike Beckerle <mbeckerle.dfdl(a)gmail.com> To: Alex Wood1/UK/IBM@IBMGB Date: 24/04/2015 15:10 Subject: Re: [DFDL-WG] OCK expression and count of 0 for a choice member.... I think this is an SDE. Choice branches cannot be optional. Optional here, does not mean minOccurs == 0, because for many occursCountKinds, that's never checked unless validation is on, and validation doesn't guide parsing anyway. Optional here means "not required by the DFDL format", as in occursCountKind cannot be 'parsed' at all, because all occurrences are then not required, and the min/maxOccurs are only examined for validation purposes, also occursCountKind cannot be 'implicit' for the same reasons, and occursCountKind 'expression' also. Wrapping the array element in a sequence doesn't solve the problem unless the sequence has a required piece of syntax such as an initiator or terminator, or a hiddenGroupRef to a not-optional (recursively) thing. Even initiator and terminator are tricky, because in a non-delimited format, those can be %WSP*; which can match nothing at all; hence, they do not "require" any syntax. 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 Fri, Apr 24, 2015 at 9:07 AM, Alex Wood1 <WOODA(a)uk.ibm.com> wrote: Hi All, Please see below for a history of the issue. This arose from fuzz testing of the IBM DFDL parser which produced a test with a coutn of 0 for an OCK expression array which was a choice member. And subsequent reference to the specification. It was not clear what the correct outcome should be in a choice where the first member is an array using OCK expression where the count resolves to 0. a.) resolve the choice to the zero length array b.) move to the next choice branch c.) throw an error Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com From: Steve Hanson/UK/IBM To: Alex Wood1/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM Date: 24/04/2015 09:19 Subject: Re: OCK expression and count of 0 for a choice member.... When I wrote the paragraph below, the one thing that troubled me was that the spec defines known-to-exist and known-not-to-exist in terms of occurrences. In the choice branch example, it is the element as a whole we are looking at. That's fine for scalar as element == occurrence but for an array it's not the same. I think the spec is missing a definition of what 'missing' means for an array element. I would say that an array element is missing if all occurrences are missing. And an array element is not missing if any occurrence has a representation (empty, nil, normal). With that in place, my paragraph makes sense, I think. I believe we have the same issue with 'parsed' and 'stopValue'. 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: Alex Wood1/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM@IBMGB Date: 23/04/2015 18:52 Subject: Re: OCK expression and count of 0 for a choice member.... Here is one interpretation... A choice is resolved by parsing the branches until one is known-to-exist as described in section 9.3.3. Section 9.3.1.2 defines known-to-exist (in the absence of a discriminator, initiator or direct dispatch) as an occurrence having empty, nil or normal representation. Section 9.3.1.3 defines known-not-to-exist (again in the absence of a discriminator, initiator or direct dispatchm or an assert) as an occurrence being missing or causing a processing error. If occursCount is zero no occurrences are looked for in the data (erratum 5.9) so the element has no representation and must be missing. Therefore a choice branch containing such an element is known-not-to-exist. So in your example, the first choice branch containing myInt is known-not-to-exist and the parser tries the next branch. This appears to contradict section 15.1.1 though. I suspect that 15.1.1 was not updated to match section 9.3 when the latter was added. If you want to make the first choice branch known-to-exist when the count is zero then I think wrapping myInt in a sequence would work. Or wrapping myInt in a complex element. Definitely one to take to the WG though, if only to correct section 15.1.1 to match section 9. 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: Alex Wood1/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Cc: Andrew Edwards/UK/IBM@IBMGB, Mark Frost/UK/IBM@IBMGB Date: 23/04/2015 16:33 Subject: OCK expression and count of 0 for a choice member.... Hi Steve Just been discussing this with Andy and Mark. I think the spec <xs:element name="Choice_Expression" dfdl:ref="config" dfdl:lengthKind="implicit"> <xs:complexType> <xs:sequence dfdl:ref="config"> <xs:element ref="myCount"></xs:element> <xs:choice dfdl:choiceLengthKind="implicit" dfdl:ref="config"> <xs:element ref="myInt" minOccurs="1" maxOccurs="3"></xs:element> <xs:element ref="myTxt"></xs:element> </xs:choice> </xs:sequence> </xs:complexType> </xs:element> Where myInt has occursCountKind="expression" occursCount="{../myCount}" A given instance of this message could have myCount==0 Is this valid? Should it resolve to 0 occurrences of myInt or move on to myTxt ? Section15 of the spec says: The Root of the Branch MUST NOT be optional. That is XSDL minOccurs MUST BE greater than 0. But in this case minOccurs is >0. Assuming this is not an error then in terms of resolving the choice section 15.1.1 says.. 15.1.1 Resolving Choices via Speculation Speculative resolution works as follows: 1) Attempt to parse the first branch of the choice. 2) If this fails with a processing error a) If a dfdl:discriminator evaluated to true earlier on this branch then the parser is 'bound' to this branch and parsing of the entire choice construct fails with a processing error. b) If the branch has a dfdl:initiator and the choice has dfdl:initiatedContent ‘yes’ then the parser is 'bound' to this branch and parsing of the entire choice construct fails with a processing error. c) Otherwise we repeat from step 1 for the next branch of the choice. 3) It is a processing error if the branches of the choice are exhausted. 4) If a branch is successfully parsed without error, then that branch's infoset becomes the infoset for the parse of the choice construct. So seems like this is 4.) we did not fail to parse myInt... However talking with mark about real scenarios that this might apply to, a choice two repeating fields with counts earlier in the data only one of which must appear. you'd expect 0 of the first means >0 of the second and visa versa... So you'd probably want 0 myInt allowed the choice to resolve to myTxt. Thoughts ? If you agree we need more clarity in he spec will forward to WG. Kind Regards, - Alex Alex Wood - Software Engineer - WebSphere Message Broker Development DFDL Development MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN. Tel: Internal 246272, External 01962 816272 Notes: Alex Wood1/UK/IBM@IBMGB e-mail: wooda(a)uk.ibm.com 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 -- 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

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clarification on choice unparsing and empty sequences
by Mike Beckerle 11 Aug '15

11 Aug '15

The spec language around how choice branches are resolved when unparsing suggests that each branch must have an element in it somewhere. On unparsing there is the question of how one identifies the appropriate schema choice branch corresponding to the data in the infoset. This is complicated by the fact that the children may not be elements. They may themselves be sequences or choices.The selection of the choice branch is as follows: The element in the infoset is used to search the choice branches in the schema, in schema definition order, but without looking inside any complex elements. If the element occurs in a branch, then that branch is selected and if subsequently a processing error occurs, this selection is not revisited (that is, there is no backtracking). To avoid any unintended behavior, all the children of a choice can be modeled as elements. However, that passage of the spec seems incomplete now to me. Though at the time it was written and reviewed it seemed to be the solution to the issue. It does imply that each model group in a choice branch has to have an element somewhere, but I couldn't find that statement explicitly in the spec, and the spec does say empty model groups are specifically allowed. 14.1 Empty Sequences A sequence having no children is syntactically legal in DFDL. In the data stream, such a sequence can have non-zero length *LeftFraming* and *RightFraming* regions, but the SequenceContent region in between must be empty. It is a processing error if the SequenceContent region of an empty sequence has non-zero length when parsing. This leaves open the issue of hidden groups e.g., <sequence dfdl:hiddenGroupRef="mygroup"/> is an empty sequence? Or does the hidden group count as if there really are children of this sequence? I suspect the latter, but need to see how others have interpreted this. XML schema does not define an empty sequence that is the content model of a complex type definition as effective content so any DFDL annotations on such a construct would be ignored. It is a schema definition error if the empty sequence is the content model of a complex type, or if a complex type has nothing in its content model at all. That makes clear that both these are SDE: <complexType><sequence/></complexType> <complexType></complexType> But it leaves many scenarios unclear still. Consider this schema fragment: .... <choice> <sequence dfdl:terminator=";"/> <element name="foo"/> </choice> <element name="bar"/> .... If we are unparsing and the infoset is just <bar> then we can compute that finding <bar> in the infoset means the first branch is selected. So we would unparse that and output a ";". However, if there is true ambiguity like: <choice> <sequence dfdl:terminator=";"/> <sequence dfdl:terminator="/"/> <element name="foo"/> </choice> <element name="bar"/> That's effectively saying on parse either a ";" or a "/" may be found. On unparse, there is nothing to guide which choice branch other than telling us if <bar> is found, that the <foo> element branch is NOT selected. However, it is ok to just output the first always (;) if the infoset has a <bar> element. However, I wanted to check and see what others interpretation of the spec is for this issue. 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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Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 - agenda item on ICU 'S' symbol
by Steve Hanson 11 Aug '15

11 Aug '15

Hi Andy Your internal ticket #630 gave rise to external ticket http://bugs.icu-project.org/trac/ticket/10962, which claims to have fixed the API docs to clarify the behaviour. S fractional second - truncates (like other time fields) to the count of letters when formatting. Appends zeros if more than 3 letters specified. Truncates at three significant digits when parsing. S SS SSS SSSS 2 23 235 2350 I can't see anywhere that addresses your point about about abutting versus non-abutting numeric symbols though? As far as DFDL spec is concerned, this is what we say today: S fractional second (see note 1) Number S SS SSS 2 24 235 There is no 'note 1', I think the note was made into a normal paragraph, which reads: Any number of fractional seconds "S" may by specified in the pattern and accepted by implementations, but an implementation is free to represent a limited number of fractional seconds internally. Excess fractional seconds are truncated, not rounded up. At least millisecond accuracy must be implemented. Unlike other fields, fractional seconds are padded on the right with zero. 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: Andrew Edwards/UK/IBM To: Steve Hanson/UK/IBM@IBMGB Date: 11/08/2015 11:56 Subject: Re: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Hi Steve Re agenda item 2 and calendar patterns with 'S', this ICU ticket from last year might be relevant - https://icu.sanjose.ibm.com/gcoctrac/ticket/630. It seems that the error reporting may also depend on whether the pattern has 'S' on it's own or next to other numeric pattern entities. i.e. 'HHmmssS' is subject to length checking, but 'HHmmss S' is not, due to the space before the 'S'. HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards(a)uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times From: Steve Hanson/UK/IBM@IBMGB To: dfdl-wg(a)ogf.org Cc: Mike Beckerle <mbeckerle(a)tresys.com>, jorge.marizan(a)gmail.com Date: 10/08/2015 18:29 Subject: [DFDL-WG] OGF DFDL WG Call Agenda 2015-08-11 Sent by: dfdl-wg-bounces(a)ogf.org Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13489?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 -- 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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OGF DFDL WG Call Agenda 2015-08-11
by Steve Hanson 10 Aug '15

10 Aug '15

Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13489?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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Confirmed: DFDL Working Group Call (11 Aug 16:00 GDT in IBM Hursley DE3S09)
by Steve Hanson 10 Aug '15

10 Aug '15

Confirmed: DFDL Working Group Call 11/08/2015 - (Repeats) Location: IBM Hursley DE3S09 Steve Hanson has confirmed this meeting Repeats This entry repeats Required: mbeckerle(a)tresys.com, mbeckerle.dfdl(a)gmail.com Optional: Alex Wood1/UK/IBM@IBMGB, Andrew Edwards/UK/IBM@IBMGB, dfdl-wg(a)ogf.org, jorge.marizan(a)gmail.com, Mark Frost/UK/IBM FYI: OGF DFDL WG weekly call dial-in details. Passcode for Participants: 5381214 Canada Toll-Free 888-426-6840 China Toll-Free 10-800-711-1071 CHINA NETCOM GROUP USERS China Toll-Free 10-800-110-0996 CHINA TELECOM SOUTH USERS France Toll-Free 0800-94-0558 Germany Toll-Free 0800-000-1018 India Toll-Free 000-800-100-1176 Ireland Toll-Free 1-800-943-427 Israel Toll-Free 1-809-417-783 United Kingdom Caller Paid 0-20-30596451 United Kingdom Toll-Free 0800-368-0638 USA Caller Paid 215-861-6239 USA Toll-Free 888-426-6840 Other international numbers available - e-mail smh(a)uk.ibm.com. OGF DFDL Home: http://www.ogf.org/dfdl Redmine DFDL: http://redmine.ogf.org/projects/dfdl-wg DFDL Getting Started: http://www.ibm.com/developerworks/library/se-dfdl/ DFDL 1.0 Spec: http://www.ogf.org/documents/GFD.207.pdf

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