Question about optional element in instance

How can I code the Instance including "optional" element?
ie. the instance is like this.

<xforms:instance id="register">

And the "name" and "sex" elements are optional.
The instance data will send to third party server,
then must pass with the following XML Schema.

<xsd:complexType name="client">
    <xsd:element name="id">...</xsd:element>
    <xsd:element name="name" minOccurs="0">
          <xsd:element name="first">...</xsd:element>
          <xsd:element name="last">...</xsd:element>
    <xsd:element name="sex" minOccurs="0">...</xsd:element>
    <xsd:element name="date">...</xsd:element>


Received on Sunday, 18 February 2007 14:55:17 UTC