<xs:restriction base="xs:NMTOKEN"> <xs:enumeration value="standard"/>
<xs:enumeration value="delta"/>
<xs:enumeration value="diamond"/>
<xs:enumeration value="white_diamond"/>
<xs:enumeration value="white_delta"/>
<xs:enumeration value="none"/>
<xs:enumeration value="plain"/>
<xs:enumeration value="concave"/>
<xs:enumeration value="convex"/>
<xs:enumeration value="circle"/>
<xs:enumeration value="dash"/>
<xs:enumeration value="transparent_circle"/>
<xs:enumeration value="skewed_dash"/>
<xs:enumeration value="t_shape"/>
</xs:restriction>