optional int and unparse formatting

[Theodore Toth]

I just started looking at daffodil and have a few questions about my
first experiment:
Here's my dfdl:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
    xmlns:xs="http://www.w3.org/2001/XMLSchema";
    xmlns:dfdl="http://www.ogf.org/dfdl/dfdl-1.0/";>

  <xs:include schemaLocation="default-dfdl-properties/defaults.dfdl.xsd" />
  <xs:annotation>
    <xs:appinfo source="http://www.ogf.org/dfdl/";>
      <dfdl:format ref="default-dfdl-properties" />
    </xs:appinfo>
  </xs:annotation>

  <xs:element name="FOO"
              dfdl:initiator="FOO/"
              dfdl:lengthKind="implicit">
<!--
              dfdl:terminator="//%NL;%WSP*;">
-->
    <xs:complexType>
      <xs:sequence dfdl:sequenceKind="ordered"
                   dfdl:separator="/"
                   dfdl:separatorPosition="infix">

        <xs:element name="elem1">
          <xs:simpleType>
            <xs:restriction base="xs:string">
              <xs:minLength value="1"/>
              <xs:maxLength value="14"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>

        <xs:element name="elem2">
          <xs:simpleType>
            <xs:restriction base="xs:string">
              <xs:pattern value="CAT|DOG|HORSE"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>

        <xs:element name="elem3">
          <xs:simpleType>
            <xs:restriction base="xs:int">
              <xs:minInclusive value="1"/>
              <xs:maxInclusive value="99999"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>

        <xs:element name="elem4" minOccurs="0" maxOccurs="1">
          <xs:simpleType>
            <xs:restriction base="xs:string">
              <xs:minLength value="1"/>
              <xs:maxLength value="20"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>

        <xs:element name="elem5" minOccurs="0" maxOccurs="1">
          <xs:simpleType>
            <xs:restriction base="xs:int">
              <xs:minInclusive value="1"/>
              <xs:maxInclusive value="999"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

</xs:schema>

Here's some test data:
FOO/GONE FISHIN/DOG/0001///

The parse fails with:
[error] Parse Error: Unable to parse xs:int from empty string
Schema context: elem5 Location line 59 column 10 in
file:/home/tedx/dfdl-test/test.dfdl.xsd
Data location was preceding byte 26

Why does it fail when elem5 has minOccurs="0"? elem5 is optional.

Then if I put a 0 before the last slash it generates:
<?xml version="1.0" encoding="UTF-8"?>
<FOO>
  <elem1>GONE FISHIN</elem1>
  <elem2>DOG</elem2>
  <elem3>1</elem3>
  <elem4></elem4>
  <elem5>0</elem5>
</FOO>

and when I unparse it generates:
FOO/GONE FISHIN/DOG/1//0

but I'd like it to output 0001 for elem3, how do I do that?

Ted