+<?xml version="1.0" encoding="ISO-8859-1"?>
+
+<!-- Copyright (C) 2000, HELM Team -->
+<!-- -->
+<!-- This file is part of HELM, an Hypertextual, Electronic -->
+<!-- Library of Mathematics, developed at the Computer Science -->
+<!-- Department, University of Bologna, Italy. -->
+<!-- -->
+<!-- HELM is free software; you can redistribute it and/or -->
+<!-- modify it under the terms of the GNU General Public License -->
+<!-- as published by the Free Software Foundation; either version 2 -->
+<!-- of the License, or (at your option) any later version. -->
+<!-- -->
+<!-- HELM is distributed in the hope that it will be useful, -->
+<!-- but WITHOUT ANY WARRANTY; without even the implied warranty of -->
+<!-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -->
+<!-- GNU General Public License for more details. -->
+<!-- -->
+<!-- You should have received a copy of the GNU General Public License -->
+<!-- along with HELM; if not, write to the Free Software -->
+<!-- Foundation, Inc., 59 Temple Place - Suite 330, Boston, -->
+<!-- MA 02111-1307, USA. -->
+<!-- -->
+<!-- For details, see the HELM World-Wide-Web page, -->
+<!-- http://cs.unibo.it/helm/. -->
+
+<!--*****************************************************************-->
+<!-- DTD FOR the MATHEMATICAL QUERY MARKUP LANGUAGE (MathQML) -->
+<!-- First draft: April 2002, Irene Schena -->
+<!--*****************************************************************-->
+
+<!--*****************************************************************-->
+<!-- This syntax is not convenient for humans to read and write, but -->
+<!-- it is for programs. -->
+<!-- XMathQL is useful for: -->
+<!-- 1) generating queries in a XML-orienting programming environment-->
+<!-- 2) embedding queries in XML documents -->
+<!-- 3) reusing queries saved in a standard format -->
+<!-- The syntax reflects the structure of the grammar productions of -->
+<!-- MathQL. -->
+<!-- The %queryexpr parameter entity is used to allow all query -->
+<!-- expression types to occur -->
+<!-- Operators are unambiguous (binary or unary), so there isn't any -->
+<!-- grouping operator. -->
+<!-- CONST is the constant string. -->
+<!--*****************************************************************-->
+
+<!ENTITY % position '(Conclusion|Hypothesis|Body|MainConclusion|
+ MainHypothesis)'>
+
+<!ENTITY % order '(ascendant|descendant)'>
+
+<!ENTITY % bool '(True|False)'>
+
+<!-- MathQL query expression declaration -->
+
+<!ENTITY % queryexpr '(Union|Intersect|Diff|SortBy|Select|Exists|Use|UsedBy|
+ ConstructorsOf|Pattern|InTheory|TheoryRefTo|TypeOf|
+ SuperTypeOf|SubTypeOf|Group)'>
+
+<!-- MathQL boolean expression declaration -->
+
+<!ENTITY % boolexpr '(AND|OR|NOT|BOOL|IS|GROUP)'>
+
+<!-- MathQL string expression declaration -->
+
+<!ENTITY % functexpr '(NAME|PROPERTY|SUPERPROPERTY|SUBPROPERTY)'>
+
+<!ENTITY % stringexpr '(CONST|POSITION|RVAR|BINDER|%functexpr;)'>
+
+
+<!-- MathQL top-element -->
+
+<!ELEMENT MathQL %queryexpr;>
+
+<!-- MathQL query expressions -->
+
+<!ELEMENT Union (%queryexpr;, %queryexpr;)>
+
+<!ELEMENT Intersect (%queryexpr;, %queryexpr;)>
+
+<!ELEMENT Diff (%queryexpr;, %queryexpr;)>
+
+<!ELEMENT SortBy (%queryexpr;, SortField)>
+
+<!ELEMENT Select (In, Where)>
+
+<!ELEMENT Exists (In, Where)>
+
+<!ELEMENT Use (%queryexpr;, Position)>
+
+<!ELEMENT Position EMPTY>
+<!ATTLIST Position
+ binder CDATA #REQUIRED>
+
+<!ELEMENT UsedBy (%queryexpr;, Position)>
+
+<!ELEMENT ConstructorsOf %queryexpr;>
+
+<!ELEMENT Pattern EMPTY>
+<!ATTLIST Pattern
+ arg CDATA #REQUIRED>
+
+<!ELEMENT InTheory (%queryexpr;, ItemType)>
+
+<!ELEMENT ItemType EMPTY>
+<!ATTLIST ItemType
+ binder CDATA #REQUIRED>
+
+<!ELEMENT TheoryRefTo %queryexpr;>
+
+<!ELEMENT TypeOf %queryexpr;>
+<!ATTLIST TypeOf
+ binder CDATA #REQUIRED>
+
+<!ELEMENT SuperTypeOf %queryexpr;>
+<!ATTLIST SuperTypeOf
+ binder CDATA #REQUIRED>
+
+<!ELEMENT SubTypeOf %queryexpr;>
+<!ATTLIST SubTypeOf
+ binder CDATA #REQUIRED>
+
+<!-- MathQL query sub-expressions -->
+
+<!ELEMENT SortField %functexpr;>
+<!ATTLIST SortField
+ order %order; #IMPLIED>
+
+<!ELEMENT In %queryexpr;>
+
+<!ELEMENT Where %boolexpr;>
+<!ATTLIST Where
+ rvar CDATA #REQUIRED>
+
+<!-- MathQL boolean expressions -->
+
+<!ELEMENT AND (%boolexpr;, %boolexpr;)>
+
+<!ELEMENT OR (%boolexpr;, %boolexpr;)>
+
+<!ELEMENT NOT %boolexpr;>
+
+<!ELEMENT IS (%stringexpr;, %stringexpr;)>
+
+<!ELEMENT BOOL EMPTY>
+<!ATTLIST BOOL
+ value %bool; #REQUIRED>
+
+<!-- MathQL string expressions -->
+<!ELEMENT CONST (#PCDATA)>
+
+<!ELEMENT RVAR EMPTY>
+<!ATTLIST RVAR
+ name CDATA #REQUIRED>
+
+<!ELEMENT BINDER EMPTY>
+<!ATTLIST BINDER
+ name CDATA #REQUIRED>
+
+<!ELEMENT POSITION EMPTY>
+<!ATTLIST POSITION
+ name %position; #REQUIRED>
+
+<!ELEMENT NAME (RVAR)>
+
+<!ELEMENT PROPERTY (RVAR|CONST)>
+<!ATTLIST PROPERTY
+ name CDATA #REQUIRED>
+
+<!ELEMENT SUPERPROPERTY (RVAR|CONST)>
+<!ATTLIST SUPERPROPERTY
+ name CDATA #REQUIRED>
+
+<!ELEMENT SUBPROPERTY (RVAR|CONST)>
+<!ATTLIST SUBPROPERTY
+ name CDATA #REQUIRED>
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