<?xml version="1.0" encoding="ISO-8859-1"?>

<!ELEMENT interps (source?,heading?,input?,interp*)>

  <!ATTLIST interps  number_of_interps CDATA #IMPLIED>

  <!ELEMENT interp (op0|op1|op2|opn)*>

    <!ATTLIST interp  size CDATA #REQUIRED
                      number CDATA #IMPLIED
                      seconds CDATA #IMPLIED>

      <!ELEMENT sym (#PCDATA)>         <!-- symbol -->
      <!ELEMENT i (#PCDATA)>           <!-- index -->
      <!ELEMENT v (#PCDATA)>           <!-- value -->
      <!ELEMENT head (i+)>
      <!ELEMENT row (i?,e+)>
      <!ELEMENT tupval (tup,v)>        <!-- tuple-value -->
      <!ELEMENT tup    (i*)>           <!-- tuple -->

      <!ELEMENT op0 (sym,v)>                          <!-- arity 0 -->
        <!ATTLIST op0 type   CDATA #REQUIRED>
                           
      <!ELEMENT op1 (sym,head,row)>                   <!-- arity 1 -->
        <!ATTLIST op1 type   CDATA #REQUIRED>
  
      <!ELEMENT op2 (sym,head,row+)>                  <!-- arity 2 -->
        <!ATTLIST op2 type   CDATA #REQUIRED>
  
      <!ELEMENT opn (sym,tupval+)>                    <!-- arity >2 -->
        <!ATTLIST opn type   CDATA #REQUIRED
                      arity  CDATA #REQUIRED>
  
