<!--
How precise shall we define the values for relationship,from etc? 
Shall we enumerate those values in a simpleType. 
-->
<?xml version="1.0" encoding="UTF-8" ?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="calendarSpecification">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="granularity" maxOccurs="unbounded" />
      </xs:sequence>
      <xs:attribute name="underlyingGranularity" type="xs:NMTOKEN" use="required" />
      <xs:attribute name="implUrl" type="xs:string" use="required" />
    </xs:complexType>
  </xs:element>

  <xs:element name="granularity">
    <xs:complexType>
      <xs:choice>
        <xs:element ref="irregularMapping" />
        <xs:element ref="regularMapping" />
      </xs:choice>
      <xs:attribute name="name" type="xs:NMTOKEN" use="required" />
    </xs:complexType>
  </xs:element>

  <xs:element name="irregularMapping">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="method" />
      </xs:sequence>
      <xs:attribute name="relationship" type="xs:NMTOKEN" use="optional" />
      <xs:attribute name="from" type="xs:NMTOKEN" use="required" />
    </xs:complexType>
  </xs:element>

  <xs:element name="method">
    <xs:complexType>
      <xs:attribute name="name" type="xs:NMTOKEN" use="required" />
    </xs:complexType>
  </xs:element>

  <xs:element name="regularMapping">
    <xs:complexType>
      <xs:attribute name="groupSize" type="xs:NMTOKEN" use="required" />
      <xs:attribute name="from" type="xs:NMTOKEN" use="required" />
    </xs:complexType>
  </xs:element>

</xs:schema>