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Action 145: 'dispatch' way of discriminating a choice for better performance (updated)
by Steve Hanson 21 Mar '12

21 Mar '12

The enveope/payload style of data format is quite common, where the envelope provides control information and the payload contains the business data. Examples are SWIFT and SAP IDocs. Typically the envelope contains a tag that identifies the payload, which can be one of many types. For SWIFT there are 300 possible types. To model this today in DFDL requires an xs:choice with each type modeled as an xs:element branch of the choice. A discriminator on each xs:element refers back to the envelope tag element thus enabling the choice to be resolved. There are two issues with this approach. 1) Performance. Even if the elements in the branches are ordered for expected frequency, there will still be cases when tens or hundreds of discriminators need to be evaluated before the choice is resolved. 2) Tight coupling. When a new type is added, a new element branch needs to be added to the choice. Action 145 proposes a mechanism to solve issue #1 and which opens the door to a possible extension to DFDL to solve issue #2 - namely a faster way to resolve a choice. Details: A new dfdl:choice property is added called dfdl:choiceBranchRef of type DFDL Expression. The expression must evaluate to a QName which corresponds to one of the element branches of the choice, and asserts 'known to exist' for that branch. Rules: - The property behaves like dfdl:ref and dfdl:hiddenGroupRef in that it is not possible to set a value in scope by a dfdl:format annotation, and is only set at its point of use. This is because there is nothing sensible that could be set in scope. But it has the benefit that adding support for the property to existing DFDL implementations will not suddenly cause errors to appear in existing DFDL schemas. - Empty string is not an allowed value. - The property is only used when parsing. - All branches must be local elements or element references. It is a schema definition error if any branch is a sequence, a choice or a group reference. - It is a processing error if the QName does not resolve to one of the branches when parsing.. - It is a schema definition error if a choice has the property set and also has dfdl:initiatedContent="yes" set locally. - Because the expression must return a QName, the expression language must provide a constructor for creating a QName from a string. XPath 2.0 provides such a function, xs:QName(), it's just not in the DFDL subset today. The string must be a lexical QName, ie, <prefix>:<name> and the prefix must be bound in what XPath calls the 'static context'. - DFDL should also include the XPath 2.0 function fn:QName() in its subset. This creates a QName from a namespace string and a name string. If you take SWIFT MT103 payload as an example, the tag in the envelope says "103" but a DFDL schema would actually model the global MT103 element with name "Document" and namespace ="urn:swift:xsd:fin.103.2011". So the dfdl:choiceBranchRef expression would have to look like: {fn:QName(fn:concat(fn:concat('urn:swift:xsd:fin.', FinMessage/Block2/MessageType), ".2011"), 'Document')} So we now have the ability to derive a QName and apply it before we start to process a choice. That makes the processing time for each branch of the choice independent of its order in the schema. We still have issue #2 so when a new payload is added, a new branch must be added to the choice. A solution to this is to allows xs:any wildcard elements back into DFDL, then provide a property dfdl:wildcardRef which works in the same way as dfdl:choiceRef. So at the point of encountering the wildcard we know its resolution in the schema. This obviously will require some further discussion, but you can see how this ability to evaluate an expression and return a QName can be used in multiple ways. Regards Steve Hanson Architect, 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

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Action 145: 'dispatch' way of discriminating a choice for better performance
by Steve Hanson 21 Mar '12

21 Mar '12

The enveope/payload style of data format is quite common, where the envelope provides control information and the payload contains the business data. Examples are SWIFT and SAP IDocs. Typically the envelope contains a tag that identifies the payload, which can be one of many types. For SWIFT there are 300 possible types. To model this today in DFDL requires an xs:choice with each type modeled as an xs:element branch of the choice. A discriminator on each xs:element refers back to the envelope tag element thus enabling the choice to be resolved. There are two issues with this approach. 1) Performance. Even if the elements in the branches are ordered for expected frequency, there will still be cases when tens or hundreds of discriminators need to be evaluated before the choice is resolved. 2) Tight coupling. When a new type is added, a new element branch needs to be added to the choice. Action 145 proposes a mechanism to solve issue #1 and which opens the door to a possible extension to DFDL to solve issue #2 - namely a faster way to resolve a choice. Details: A new dfdl:choice property is added called dfdl:choiceBranchRef of type DFDL Expression. The expression must evaluate to a QName which corresponds to one of the element branches of the choice, and asserts 'known to exist' for that branch. Rules: - The property behaves like dfdl:ref and dfdl:hiddenGroupRef in that it is not possible to set a value in scope by a dfdl:format annotation, and is only set at its point of use. This is because there is nothing sensible that could be set in scope. But it has the benefit that adding support for the property to existing DFDL implementations will not suddenly cause errors to appear in existing DFDL schemas. - Empty string is not an allowed value. - The property is only used when parsing. - All branches must be local elements or element references. It is a schema definition error if any branch is a sequence, a choice or a group reference. - It is a processing error if the QName does not resolve to one of the branches when parsing.. - It is a schema definition error if a choice has the property set and also has dfdl:initiatedContent="yes" set locally. - Because the expression must return a QName, the expression language must provide a constructor for creating a QName from a namespace string and a name string. If you take SWIFT MT103 payload as an example, the tag in the envelope says "103" but a DFDL schema would actually model the global MT103 element with name "Document" and namespace ="urn:swift:xsd:fin.103.2011". So the dfdl:choiceBranchRef expression would have to look like: {fn:QName(fn:concat(fn:concat('urn:swift:xsd:fin.', FinMessage/Block2/MessageType), ".2011"), 'Document')} So we now have the ability to derive a QName and apply it before we start to process a choice. That makes the processing time for each branch of the choice independent of its order in the schema. We still have issue #2 so when a new payload is added, a new branch must be added to the choice. A solution to this is to allows xs:any wildcard elements back into DFDL, then provide a property dfdl:wildcardRef which works in the same way as dfdl:choiceRef. So at the point of encountering the wildcard we know its resolution in the schema. This obviously will require some further discussion, but you can see how this ability to evaluate an expression and return a QName can be used in multiple ways. Regards Steve Hanson Architect, 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

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Action 167: textNumberPatterns with P, V, # - allowable combinations
by Steve Hanson 21 Mar '12

21 Mar '12

Last week we agreed that disallowing text number patterns that contained a # symbol and either a P or V symbol was too restrictive. Accordingly the following rules are proposed to control when # may be used in the same pattern as P or V to ensure an unambiguous pattern. a) Pattern must not have # symbols to the right of the V symbol. b) If pattern has P symbols at the left end, then there must be as many 0 symbols adjacent to the rightmost P symbol as there are P symbols. c) If pattern has P symbols at the right end, there are no restrictions. If a) or b) are violated it is a schema definition error. Regards Steve Hanson Architect, 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

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OGF DFDL WG Call Agenda 2012-03-21 - Call moved to Wed & time changed !!
by Steve Hanson 20 Mar '12

20 Mar '12

Please find agenda attached for the above call on GridForge at https://forge.ogf.org/sf/docman/do/downloadDocument/projects.dfdl-wg/docman… Call is on Wed 4pm UK (12noon Eastern) for this week only. Regards Steve Hanson Architect, 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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Rescheduled: OGF DFDL Working Group weekly call (21 Mar 16:00 GMT in IBM Hursley DE2K09)
by Steve Hanson 19 Mar '12

19 Mar '12

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 GridForge DFDL: http://forge.ogf.org/projects/dfdl-wg/ Steve is on vacation Tuesday afternoon UK, so we will try and move the call to Wednesday. If enough folk can make the new time, we'll have the call, otherwise it will be cancelled. If you can make the new time, please respond in the affirmative.

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XML Schema do type references have to be qualified?
by Mike Beckerle 19 Mar '12

19 Mar '12

Suman, In and XMLSchema/DFDLSchema do I have to qualify the names of types? We have a bunch of test schemas written roughly like the example below. They all have the default unprefixed namespace as XML Schema's namespace. They also all have a target namespace. But some or all of the type references to named types use unqualified names. In my mind, that means they would be assumed to be in the XML Schema namespace, not the targetNamespace. On the other hand, the XML Schema validator doesn't complain. But that just means the schema is valid, not necessarily meaningful. Example here: <schema xmlns="http://www.ogf.org/dfdl/dfdl-1.0/XMLSchemaSubset" targetNamespace="http://example.com"> <element name="foo" type="bar"/> <complexType name="bar"> <sequence/> </complexType> </schema> Mike Beckerle | OGF DFDL WG Co-Chair Tel: 781-330-0412

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Escape scheme properties that can be expressions
by Steve Hanson 14 Mar '12

14 Mar '12

The spec allows the escapeCharacter and escapeEscapeCharacter of DFDL escapeScheme to be expressions, in case the characters are supplied dynamically in the data stream. However given that escape schemes are defined globally, should these properties be permitted to take relative paths in the expression? Today the spec implicitly allows this, meaning an implementation can not entirely validate an escapeScheme annotation up front, but must validate escapeCharacter and escapeEscapeCharacter at each point of use. I'm not sure it makes much sense for the path to be anything than absolute. Regards Steve Hanson Architect, 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

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OGF DFDL WG Call Minutes 2012-03-13
by Steve Hanson 13 Mar '12

13 Mar '12

Please find minutes from the above call on GridForge at https://forge.ogf.org/sf/docman/do/downloadDocument/projects.dfdl-wg/docman… Errata document has been updated to version 8 and may be found via https://forge.ogf.org/sf/projects/dfdl-wg Regards Steve Hanson Architect, DFDL, IBM SWG Co-Chair, OGF DFDL Working Group Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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OGF DFDL WG Call Agenda 2012-03-13 - Due to DST call is at 11am Eastern
by Steve Hanson 13 Mar '12

13 Mar '12

Please find agenda attached for the above call on GridForge at https://forge.ogf.org/sf/docman/do/downloadDocument/projects.dfdl-wg/docman… . Due to DST call is at 11am Eastern not 10am Regards Steve Hanson Architect, 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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textNumberPattern P, V, and double, float types
by Mike Beckerle 13 Mar '12

13 Mar '12

The P and V pattern characters have this in their meaning description "Only used with decimal, float and double simple types." I'm just inquiring to confirm whether we really want to deal with this for float and double. I understand the need for this for decimal, but floating point and "implied decimal point" seem to be conflicting concepts, and floating point also has its own "scaling", called the "exponent". ...mikeb -- Mike Beckerle | OGF DFDL WG Co-Chair Tel: 781-330-0412

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