Mike, responses in-line below.

Regards

Steve Hanson

IBM Hybrid Integration, Hursley, UK
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
smh@uk.ibm.com
tel:+44-1962-815848
mob:+44-7717-378890
Note: I work Tuesday to Friday

From: Mike Beckerle <mbeckerle.dfdl@gmail.com>
To: Steve Hanson <smh@uk.ibm.com>
Cc: DFDL-WG <dfdl-wg@ogf.org>
Date: 04/10/2018 00:50
Subject: Part 2 - Re: Action 307 - Demonstrate implementation interoperability

Based on Daffodil JIRA ticket backlog, and documentation at https://daffodil.apache.org/unsupported/, below are DFDL non-core features that are not supported by Daffodil, but that seem to be supported by IBM DFDL (based on my not finding anything that says they aren't implemented), and so are possibly in use in DFDL schemas we will need to use for interoperability testing.

Please advise if IBM DFDL does *not* implement any of these.

* default, fixed - for defaulting values at parse time - Daffodil support for this is partial at parse time, unsupported at unparse time. The fixed attribute isn't supported at all.
* unordered sequences. IBM DFDL does not support default/fixed when parsing (see other thread).
* byte-value entities - in contexts other than fillByte
* ICU symbols 'u' and 'I' in calendarPattern
* binaryFloatRep 'ibm390Hex'
* documentFinalTerminatorCanBeMissing
* textStandardBase - with value not equal to 10
* lengthKind 'prefixed', and prefixIncludesPrefixLength, prefixLengthType - Note IBM restricts prefixLengthType to a type that itself cannot be prefixed. Correct.
* assert with failure type 'recoverableError'
* calendarObserveDST
* calendarCenturyStart
* textNumberPattern 'V' and 'P' symbols
* CCSID for specifying dfdl:encoding
* nilKind 'literalValue' for binary data
* choiceLengthKind 'explicit' and choiceLength
* separatorSuppressionPolicy - behaviors for these in Daffodil are known to be both non-standard currently and also different from IBM DFDL. This needs correcting. IBM DFDL does not support 'trailingEmptyStrict'
.

The above list (after review/correction) needs to be crossed with the published DFDL schemas on github that were published by IBM. The features required to run those DFDL schemas are required for Daffodil to implement before the interoperability demonstration.

Below are features of DFDL I believe neither IBM DFDL nor Daffodil implement, and as they are non-core, they need not be implemented by either for interoperability testing:

* lengthKind 'endOfParent'
* nilKind 'logicalValue' IBM DFDL implements this.
* occursCountKind 'stopValue' (and occursStopValue)
* textBiDi - and other related biDi properties
* useNilForDefault IBM DFDL implements this
* floating
* fn:exactlyOne function
* fn:namespace-URI() function
* dfdl:escapeCharacterPolicy 'delimiters' - daffodil doesn't implement this property at all.

Below are features of Daffodil that are not implemented by IBM DFDL and so cannot be used in schemas created using Daffodil that intend to be interoperable. These are either easy to work around, or impossible to work around, so are not a big deal, they just have to be kept in mind if considering a DFDL schema for use in interoperability testing. This includes schemas published on github, for image formats, CSV, etc., and a number of the FOUO schema published on DI2E.net/forge.mil - some of those quite possibly can work with IBM DFDL, and if they can do so, they should be modified so that they can be included in the interoperability testing.

The list below mostly comes from https://www.ibm.com/support/knowledgecenter/en/SSMKHH_10.0.0/com.ibm.etools.mft.doc/df00150_.htm

* calendarTimeZone specified as "" (empty string) - This is the most problematic one, so I've put it first. The predefined DFDL named format that is supplied with Daffodil and used as a starting point by most schemas has calendarTimeZone="". This is because customers didn't like that their datetimes were all being appended with "+00:00" for UTC time zone (in the infoset) when the data simply didn't specify a time zone. Schemas intended for interoperability testing should specify 'UTC' for this property.
* calendarTimeZone specified as an Olson format time zone
* inputValueCalc, outputValueCalc
* hiddenGroupRef
* Asserts and discriminators on simple type definitions or global element definitions
* fn:concat with more than 4 arguments
* non-8-bit charset encodings
* bitOrder not mostSignifcantBitFirst
* '@' in textNumberPattern (TBD: unsure if Daffodil has this)
* "_" in calendarLanguage
* calendarLanguage an expression
* assert & discriminator messages an expression
* binaryBooleanTrueRep as "" (empty string)
* checks for binary packed numbers with length units 'bits' and not a multiple of 4 length, and similarly for alignmentUnits bits and alignment not multiple of 4. (relevant to negative tests only)
* lengthKind 'implicit' complex elements inside lengthKind 'delimited' complex elements.

Additionally IBM DFDL contains these bugs in its expression processing:
1) Path locations are not correctly validated. Specifically, array elements without predicates and references into other choice branches are not flagged as errors.
2) In DFDL expression functions, the namespace prefixes for http://www.w3.org/2001/XMLSchema and http://www.w3.org/2005/xpath-functions" must be 'xs' and 'fn' respectively, even if not declared.
3) In DFDL expressions, namespace prefixes in paths are ignored and matching is against element name only.

For interoperability testing therefore:
- For 1) avoid the use of either example
- For 2) always declare xmlns:xs and xmlns:fn and always use those prefixes in expressions
- For 3) avoid sibling elements that have same name but different namespace; use elementFormDefault="unqualified" to avoid namespaces for local elements altogether

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