Hi Mike

Yes I think your interpretation of the spec is correct. If you removed dfdl:initiatedContent and used a discriminator on foo instead then you have an analogous situation.

The awkward scenario is 4, when the points of uncertainty vary depending on the occurrences.

Possibly writing Scenario 4 as follows makes things clearer:

<xs:choice dfdl:initiatedContent="yes">
   ....
   <xs:element name="foo" minOccurs="5" maxOccurs="5" dfdl:initiator="foo:" dfdl:occursCountKind="fixed".../>
   <xs:element name="foo" minOccurs="0" dfdl:initiator="foo:" dfdl:occursCountKind="implicit".../>
   ...
</xs:choice>

When I get a chance I will create a schema for your scenarios, and see what IBM DFDL does and what it outputs in its trace.

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: DFDL-WG <dfdl-wg@ogf.org>
Date: 14/06/2019 22:57
Subject: [DFDL-WG] Tracker 299 and clarifications needed for dfdl:initiatedContent="yes" behaviors
Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org>

Clarifications around initiatedContent="yes", choices, and array elements

DFDL spec says in Section 15 that the root of a choice branch must not be optional, meaning minOccurs cannot be 0.
This was questioned and resulted in tracker 299. The last comment there suggests a need to revisit.

Here's the link: https://redmine.ogf.org/issues/299

The additional clarification I seek is whether I have properly understood how dfdl:initiatedContent works in scenarios involving a combination of choices with
array elements.

Consider this schema fragment:


<xs:choice dfdl:initiatedContent="yes">
   ....
   <xs:element name="foo" minOccurs="5" dfdl:initiator="foo:" dfdl:occursCountKind="parsed".../>
   ...
</xs:choice>
When parsing this choice, if you encounter "foo:" in the data stream, that discriminates two things: the choice itself, and the first occurrence of the array foo. Both that choice branch (aka the array), and the first occurrence of the array are "known to exist" per section 9.3.1.1.
Subsequent occurrences of additional foo elements with their initiators "foo:" discriminate only the array occurrences. The minOccurs="5" is ignored (except for validation)


<xs:choice dfdl:initiatedContent="yes">
   ....
   <xs:element name="foo" minOccurs="5" dfdl:initiator="foo:" dfdl:occursCountKind="fixed".../>
   ...
</xs:choice>
When parsing this choice, if you encounter "foo:" in the data stream, that discriminates the choice, but only for the first occurrence of element foo. There is no point of uncertainty for the array. Subsequent occurrences of element foo do not discriminate anything. There must be exactly 5 occurrences of element foo with initiators.


<xs:choice dfdl:initiatedContent="yes">
   ....
   <xs:element name="foo" minOccurs="5" dfdl:initiator="foo:" dfdl:occursCountKind="expression".../>
   ...
</xs:choice>
When parsing this choice, if you encounter "foo:" that discriminates the choice, but there are no points of uncertainty for the array. MinOccurs is ignored (except for validation).
Subsequent occurrences of element "foo" do not discriminate anything.


<xs:choice dfdl:initiatedContent="yes">
   ....
   <xs:element name="foo" minOccurs="5" dfdl:initiator="foo:" dfdl:occursCountKind="implicit".../>
   ...
</xs:choice>
When parsing this choice, if you encounter "foo:" that discriminates the choice, but there is no point of uncertainty for the array until 5 occurrences have been parsed.
Once the occurs index is 6 then if you encounter "foo:" that discriminates the occurrence of the array element foo, but the choice is already decided.

I raise these scenarios because they show that there is quite a bit of complexity associated with dfdl:initiatedContent if viewed as a mechanism for setting discriminators.
Sometimes more than one discriminator must be set, other times only one, and sometimes it depends on the array index.

So the question is: Is my understanding of the above scenarios correct?

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
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