+
+<!-- CONVERSION CONSTRAINT SYSTEM -->
+
+<!ENTITY % cc '(ToPositive|ToOne|ToNext)'>
+
+<!ENTITY % ccs '(%cc;*)'>
+
+<!ELEMENT ToPositive EMPTY>
+<!ATTLIST ToPositive
+ arity NMTOKEN #IMPLIED
+ mark NMTOKENS #IMPLIED
+>
+
+<!ELEMENT ToOne EMPTY>
+<!ATTLIST ToOne
+ arity NMTOKEN #IMPLIED
+ mark NMTOKENS #IMPLIED
+>
+
+<!ELEMENT ToNext EMPTY>
+<!ATTLIST ToNext
+ arity NMTOKEN #IMPLIED
+ prec NMTOKENS #IMPLIED
+ next NMTOKENS #IMPLIED
+>
+
+<!ELEMENT CCS %ccs;>
+<!ATTLIST CCS
+ uri CDATA #REQUIRED
+>