Hmmm, maybe not.  I said:

> The unordered sequence can be modeled with a data array

Yet when implemented in MBTK, it throws a fatal error:

fatal: CTDP3148E: Infinite loop at offset 3: The DFDL parser cannot process array element 'ABCarray' because maxOccurs is unbounded and the length of the previous occurrence was zero. 

I think what happens is that on the last pass through the array, it doesn’t find a, b, or c, so it throws a fatal error.

So is this a bug in MBTK?  Or can DFDL not model an unordered sequence?  Or am I just doing it wrong?

Here’s a sample DFDL schemas that illustrates the point:

<?xml version="1.0" encoding="UTF-8"?>

<xsd:schema xmlns:dfdl="http://www.ogf.org/dfdl/dfdl-1.0/"

xmlns:fmt="http://www.ibm.com/dfdl/GeneralPurposeFormat"

xmlns:ibmSchExtn="http://www.ibm.com/schema/extensions" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:import namespace="http://www.ibm.com/dfdl/GeneralPurposeFormat"

schemaLocation="IBMdefined/GeneralPurposeFormat.xsd" />

<xsd:element ibmSchExtn:docRoot="true" name="ABC">

<xsd:complexType>

<xsd:sequence dfdl:separator="">

<xsd:annotation>

<xsd:appinfo source="http://www.ogf.org/dfdl/">

<dfdl:sequence />

</xsd:appinfo>

</xsd:annotation>

<xsd:element dfdl:occursCountKind="implicit" maxOccurs="unbounded"

minOccurs="1" name="ABCarray">

<xsd:complexType>

<xsd:sequence dfdl:separator="">

<xsd:element dfdl:length="1" dfdl:lengthKind="explicit"

dfdl:occursCountKind="implicit" fixed="a" minOccurs="0" name="a"

type="xsd:string" />

<xsd:element dfdl:length="1" dfdl:lengthKind="explicit"

dfdl:occursCountKind="implicit" fixed="b" minOccurs="0" name="b"

type="xsd:string" />

<xsd:element dfdl:length="1" dfdl:lengthKind="explicit"

dfdl:occursCountKind="implicit" fixed="c" minOccurs="0" name="c"

type="xsd:string" />

</xsd:sequence>

</xsd:complexType>

</xsd:element>

</xsd:sequence>

</xsd:complexType>

</xsd:element>

<xsd:annotation>

<xsd:appinfo source="http://www.ogf.org/dfdl/">

<dfdl:format ref="fmt:GeneralPurposeFormat" />

</xsd:appinfo>

</xsd:annotation>

</xsd:schema>

Test with “abc” as sample input.

From: Garriss Jr., James P.
Sent: Tuesday, March 05, 2013 8:43 AM
To: dfdl-wg@ogf.org
Subject: unordered sequence with constrained occurrences

Suppose text data has 3 constructs:  a, b, and c.

· a must occur 1 time

· b can occur 0 or 1 time

· c can occur any number of times, 0 or more

These 3 constructs can appear in any order.

So these are valid inputs:

abc

a

bcccca

But these are not:

ccbcc  

abbc

abcabc

Can data like this be modeled with DFDL?

The unordered sequence can be modeled with a data array, like this:

Array (0 to unbounded)

Sequence

  a (0 to 1)

  b (0 to 1)

  c (0 to 1)

/Sequence

/Array

But I don’t know how to constrain the total number of occurrences. 

Appreciate any ideas!