--- /dev/null
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- DTD for persistent lambda-delta logical data -->
+
+<!-- TERMS -->
+
+<!ENTITY % leaf '(Sort|LRef|GRef)'>
+
+<!ENTITY % node '(Cast|Appl|Abst|Abbr|Void)'>
+
+<!ENTITY % term '(%node;*,%leaf;)'>
+
+<!ENTITY % terms '(%term;*)'>
+
+<!ELEMENT Sort EMPTY>
+<!ATTLIST Sort
+ position NMTOKEN #REQUIRED
+ name NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT LRef EMPTY>
+<!ATTLIST LRef
+ position NMTOKEN #REQUIRED
+ offset NMTOKEN #IMPLIED
+ name NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT GRef EMPTY>
+<!ATTLIST GRef
+ uri CDATA #REQUIRED
+ name NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT Cast %term;>
+<!ATTLIST Cast
+ arity NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT Appl %terms;>
+<!ATTLIST Appl
+ arity NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT Abst %terms;>
+<!ATTLIST Abst
+ level NMTOKEN #IMPLIED
+ name NMTOKENS #IMPLIED
+ arity NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT Abbr %terms;>
+<!ATTLIST Abbr
+ name NMTOKENS #IMPLIED
+ arity NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!ELEMENT Void EMPTY>
+<!ATTLIST Void
+ name NMTOKENS #IMPLIED
+ arity NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta CDATA #IMPLIED
+>
+
+<!-- ENVIRONMENT ENTRIES -->
+
+<!ENTITY % entity '(ABST|ABBR)'>
+
+<!ELEMENT ABST %term;>
+<!ATTLIST ABST
+ uri CDATA #REQUIRED
+ level NMTOKEN #IMPLIED
+ name NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta NMTOKENS #IMPLIED
+ lang NMTOKEN "en-US"
+ info CDATA #IMPLIED
+>
+
+<!ELEMENT ABBR %term;>
+<!ATTLIST ABBR
+ uri CDATA #REQUIRED
+ name NMTOKEN #IMPLIED
+ mark NMTOKEN #IMPLIED
+ meta NMTOKENS #IMPLIED
+ lang NMTOKEN "en-US"
+ info CDATA #IMPLIED
+>
+
+<!ELEMENT ENTITY %entity;>
+<!ATTLIST ENTITY
+ xmlns CDATA #FIXED "http://lambda-delta.info"
+ hierarchy NMTOKEN #REQUIRED
+ options NMTOKENS #IMPLIED
+>
+
+<!-- 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
+ xmlns CDATA #FIXED "http://lambda-delta.info"
+ uri CDATA #REQUIRED
+>