How to create a hidden group for 0-7 padding bits?

[Costello, Roger L.]

Hello DFDL community,

I swore that I would not use hidden groups, but I just can't bear to display 
padding bits in the XML output.

My input file is binary. At the end of a section, there may be 0-7 padding 
bits. The following doesn't work because outputValueCalc is not allowed on an 
array:

<xs:group name="padding7Bits">
    <xs:sequence>
        <xs:element name="padding" minOccurs="0" maxOccurs="7" 
                dfdl:occursCountKind="implicit" type="unsignedint1" 
                dfdl:outputValueCalc="{0}" />
    </xs:sequence>
</xs:group>

Next, this doesn't work because outputValueCalc is not allowed on optional 
elements:

<xs:group name="padding7Bits">
    <xs:sequence>
        <xs:element name="bit0" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit1" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit2" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit3" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit4" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit5" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
        <xs:element name="bit6" minOccurs="0" dfdl:occursCountKind="implicit" 
                type="unsignedint1" dfdl:outputValueCalc="{0}" />
    </xs:sequence>
</xs:group>

So, how do I declare the hidden group?

/Roger