- dfdl-wg - lists.ogf.org

Clarification: attributes in DFDL schema that are used not for data, but for other non-DFDL annotation elements.
by Mike Beckerle 20 Feb '18

20 Feb '18

Interesting issue. DFDL doesn't allow use of attributes. But we have a user that has a DFDL schema to which they also want to add other non-DFDL annotations. Like DFDL itself, this other annotation language has a variety of annotation elements that appear inside xs:appinfo blocks with specific source attribute specified. A DFDL processor should be ignoring these. Those other annotation elements have attributes (as do DFDL's annotation elements.) But Daffodil issues a schema definition error on the attribute declarations of this other annotation-language schema. This because it has no way of telling if these attribute declarations are for use *only* in annotations that it will ignore, or if they are used for modeling data. Question is: Is it acceptable for a DFDL annotation to just say "Nowhere in the extended schema - all files - can there be any attribute declarations.", or do we need to accommodate attributes and in fact every XSD construct that DFDL disallows, so long as they're not being used to model data? Really there's two questions here. First, does the DFDL specification take (or need to take) a position on this. Second, what's a practical choice for a DFDL implementation like Daffodil to take here. ...mikeb 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 today 2018-02-20 - cancelled
by Steve Hanson 20 Feb '18

20 Feb '18

Apologies for late notice - a meeting conflict means I can't make the call today Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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Cancelled: OGF DFDL Working Group Call
by Steve Hanson 20 Feb '18

20 Feb '18

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Review/Feedback wanted on proposal: Data Streaming for base64 and other Layered Transformations
by Mike Beckerle 15 Feb '18

15 Feb '18

We have a great deal of demand for the ability to describe data formats that include layered transformations - that is, regions within the data that need to be algorithmically transformed before parsing and after unparsing. The IETF data formats make extensive use of line folding, base64, etc. Many formats allow compressed payloads. All these are examples of "layering" where a region of the data stream can be identified, algorithmically transformed, and then subsequently further parsed. (The inverse process for unparsing obviously.) Our draft proposal, that we are hoping to implement in Daffodil, is here: https://cwiki.apache.org/confluence/display/DAFFODIL/Proposal%3A+Data+Strea… Any feedback on this is very welcome, and can be addressed to dfdl-wg mailing list. 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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Latest OGF DFDL WG Call Minutes
by Steve Hanson 06 Feb '18

06 Feb '18

Please find minutes from the latest call at https://redmine.ogf.org/projects/dfdl-wg/news Regards Steve Hanson IBM Hybrid Integration Architect, IBM DFDL, Co-Chair, OGF DFDL Working Group smh(a)uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890

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Confirmed: OGF DFDL Working Group Call (6 Feb 15:00 GMT)
by Steve Hanson 06 Feb '18

06 Feb '18

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Agenda for next OGF DFDL WG Call
by Steve Hanson 06 Feb '18

06 Feb '18

Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13572?download= Regards Steve Hanson IBM Hybrid Integration Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh(a)uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890

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Action Item: Versioning mechanism for DFDL v2.0 features/changes
by Mike Beckerle 23 Jan '18

23 Jan '18

There are some features now under discussion which will most likely not be part of the DFDL v1.0 standard, but a subsequent version 2.0 of the standard. Implementations may have these features prior to the existence of that draft version of the DFDL standard; hence, a mechanism for indicating the support, and requirements that implies, on DFDL schemas is needed in order for these v2.0 features to be introduced. The purpose of the versioning mechanism is to provide access to DFDL v2.0 features, while maintaining also backward compatibility with DFDL v1.0 schemas. For example, new DFDL format properties may be added to the DFDL v2.0 version; however, those properties are not required to be specified unless the version of the schema is specifically set to indicate it is using version 2.0 features. Also, deprecated features should only generate deprecation warnings if the user is requesting version 2.0 of DFDL, and should be silent otherwise. Proposal: New attribute on the dfdl:format annotation: DFDLVersion with valid values "1", "2". All values are reserved for future use. The DFDLVersion, if unspecified, defaults to "1" which means the implementation is of the DFDL v1.0 specification. If the DFDLVersion is "2", then new requirements for version 2.0 of DFDL may be enforced on the schema, and schema definition errors will result if version 2.0 requirements are not met. DFDL Version 1.0 features that are deprecated will generate warnings. Example: <dfdl:format DFDLVersion="2" .../> Example: <dfdl:defineFormat name="myV2Format"> <dfdl:format DFDLVersion="2" .../> </dfdl:defineFormat> The DFDLVersion is not a format property and is not scoped. It can be added to a named format definition which is then referenced in the usual manner for named format definitions. Backward Compatibility Requirement DFDL Implementations that provide version 2.0 functionality must also provide DFDL v1.0 compatibility. That is, version 2.0 subsumes and extends version 1.0. Mixed Version Schemas If a schema consists of multiple schema documents, and their respective dfdl:format annotations do not all contain the same value for the DFDLVersion attribute, then the schema is said to be "mixed version". This is allowed. A named dfdl:format carrying DFDLVersion "2" may not be referenced from a DFDL Schema document having DFDLVersion "1". The opposite is allowed: A named dfdl:format carrying DFDLVersion="1" or lacking the DFDLVersion attribute may be referenced from a DFDL Schema having DFDLVersion="2". There are really 3 ways that DFDL version 2.0 can differ from version 1.0, and these are that new features are added, old features are deprecated, or old features are removed. This latter is quite undesirable, but will be considered a possibility for purpose of discussion this versioning system. These will commonly be in combination such as if an old feature is deprecated with the replacement feature being added. These will now be discussed separately, with the emphasis on how mixed version schemas must work. New Features Added Each new required DFDL property introduced for version 2.0 will be defined along with what is called its "version 1.0 default value". When a mixed version schema exists, the DFDL v1.0 parts of it behave as if any required DFDLVersion 2 properties have their version 1.0 default value defined, at top level of the schema (as if defined with that default value in each DFDLVersion 1 schema document's dfdl:format annotation). Features Removed Incompatibilities are to be avoided wherever possible, and may not be needed at all. However, there is still the possibility that some feature will want to be entirely removed and replaced by something better, and in that case the versioning scheme needs to be able to support this. In that situation, the schema definition error for version 2 is only generated when a schema has DFDLVersion 2 specified (in dfdl:format explicitly, or by reference to a named format carrying or referencing DFDLVersion 2). Mixed schemas that contain schema documents entirely using version 1 of DFDL do not generate this schema definition error. Features deprecated Deprecation warnings are generated only when a DFDLVersion="2" attribute is present or is incorporated by reference (to a named format). A version 1 schema that is incorporated with a version 2 DFDL schema but is not modified in any way, does not generate deprecation warnings about version 1.0 features that have been deprecated in version 2.0. (Most likely deprecations would be revising property names or value enums for clarity.) Implementations may provide mechanisms for suppressing warnings. These are implementation dependent. Version 1.0 Existing Deprecations and Compatibility During the process of standardization for DFDL v1.0 a number of properties names were changed. DFDL version 1.0 implementations accept both the old and new property names. (Example: dfdl:separatorSuppressionPolicy, which replaced an older property name.) DFDL schemas that specify DFDLVersion="2" will not accept the older property names, and it is a schema definition error if the old (pre DFDL v1.0) property names are used. Properly constructed mixed version schemas can still depend on the older property names in the version 1.0 parts of the schema. ------------------------------ 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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Latest OGF DFDL WG Call Minutes
by Steve Hanson 23 Jan '18

23 Jan '18

Please find minutes from the latest call at https://redmine.ogf.org/projects/dfdl-wg/news Regards Steve Hanson IBM Hybrid Integration Architect, IBM DFDL, Co-Chair, OGF DFDL Working Group smh(a)uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890

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Agenda for next OGF DFDL WG Call
by Steve Hanson 23 Jan '18

23 Jan '18

Please find agenda for call on Redmine at https://redmine.ogf.org/dmsf_files/13571?download= Regards Steve Hanson IBM Hybrid Integration Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh(a)uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890

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