present 

An enumerated type indicating the presence or absence of an allele.

          N: a particular allele was tested for and found not to be a 
             possibility
          U: the given allele was not tested for
          Y: (default) the given allele was tested for and found to be a 
             possible result

Simple Type Information

Used By

Attribute allele/@present

Source 

<xs:simpleType name="present">
  <xs:annotation>
    <xs:documentation>An enumerated type indicating the presence or absence of an allele. N: a particular allele was tested for and found not to be a possibility U: the given allele was not tested for Y: (default) the given allele was tested for and found to be a possible result</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:string">
    <xs:enumeration value="N"/>
    <xs:enumeration value="U"/>
    <xs:enumeration value="Y"/>
  </xs:restriction>
</xs:simpleType>