Seek your recommendation on modeling this input

[Costello, Roger L.]

Hello DFDL community,


  *   The input is binary.
  *   There is a sequence of sections.
  *   Section 1 is identified by the 2-bit code 01. There are zero or more of 
Section 1. The content of each Section 1 is a 3-bit unsigned int followed by a 
1-bit unsigned int.
  *   Section 2 is identified by the 2-bit code 10. There are zero or more of 
Section 2. The content of each Section 2 is a 4-bit unsigned int followed by a 
2-bit unsigned int.
  *   Section 3 is identified by the 2-bit code 11. There are zero or more of 
Section 4. The content of each Section 3 is a 4-bit unsigned int followed by a 
5-bit unsigned int.
  *   Afterwards, there is padding to fill the last byte.

One way to model the input is as a sequence of arrays:

<xs:element name="input">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="Section_1" type="Section_1_type"
                       minOccurs="0" maxOccurs="unbounded"
                        dfdl:occursCountKind="implicit"/>
            <xs:element name="Section_2" type="Section_2_type"
                        minOccurs="0" maxOccurs="unbounded"
                        dfdl:occursCountKind="implicit"/>
            <xs:element name="Section_3" type="Section_3_type"
                        minOccurs="0" maxOccurs="unbounded"
                        dfdl:occursCountKind="implicit"/>
            <xs:sequence dfdl:hiddenGroupRef="padToByteBoundary" />
        </xs:sequence>
    </xs:complexType>
</xs:element>

A second way to model the input is as a repeatable section that contains a 
choice:

<xs:element name="input">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="Section" maxOccurs="unbounded"
                        dfdl:occursCountKind="implicit">
                <xs:complexType>
                    <xs:sequence>
                        <xs:element name="code" type="unsignedint2" />
                        <xs:choice dfdl:choiceDispatchKey="{xs:string(./code)}"
                                    dfdl:choiceLengthKind="implicit">
                            <xs:element name="Section_1" type="Section_1_type"
                                    dfdl:choiceBranchKey="1" />
                            <xs:element name="Section_2" type="Section_2_type"
                                    dfdl:choiceBranchKey="2" />
                            <xs:element name="Section_3" type="Section_3_type"
                                    dfdl:choiceBranchKey="3" />
                        </xs:choice>
                    </xs:sequence>
                </xs:complexType>
            </xs:element>
            <xs:sequence dfdl:hiddenGroupRef="padToByteBoundary" />
        </xs:sequence>
    </xs:complexType>
</xs:element>

Which way do you recommend and why?

/Roger