obj STRING is
  pr QID .
  sort String .
  subsort Id < String .
  op _ _ : String String -> String [ assoc ] .
endo

obj QUERY is
  pr INT .
  sort Query .
  op price > _ : Int -> Query .
endo

***> DTD for Book Store 1
obj BOOKSTORE1-DTD is
   pr QID .
   pr INT .
   pr STRING .
   sorts Document Book BookList Title Author Price .
   subsort Book < BookList .
   op nil : -> BookList .
   op _ _ : BookList BookList -> BookList [ assoc idr: nil ].
   op <document> _ </document> : BookList -> Document .
   op <book> _ _ _ </book> : Title Author Price -> Book .
   op <title> _ </title> : String -> Title .
   op <author> _ _ </author> : Id Id -> Author .
   op <price unit="$"> _ </price> : Int -> Price .
endo

***> XML for Book Store 1
obj BOOKSTORE1-XML is
   pr BOOKSTORE1-DTD .
   op doc1 : -> Document .
   eq doc1 = <document>
	       <book>
                   <title>  'Inside 'XML </title>
	           <author> 'Steven 'Holzner </author>
                   <price unit="$">  39 </price>
	       </book>
	       <book>
                   <title>  'Professional 'XML 'Databases  </title>
	           <author> 'Kevin 'Williams </author>
                   <price unit="$">  53 </price>
	       </book>
	       <book>
                   <title>  'Learning 'XML   </title>
	           <author> 'Erik 'Ray  </author>
                   <price unit="$">  41 </price>
	       </book>
	     </document> .
endo

***> query
obj QUERY-BOOKSTORE1 is
   pr BOOKSTORE1-XML .
   pr QUERY .
   op query : Document Query -> BookList .
   op query : BookList Query -> BookList .
   var BL : BookList .
   vars N N1 N2 : Int .
   var T : Title .
   var A : Author .
   var P : Price .
   eq query(<document> BL </document>, price > N) = query(BL, price > N) .
   cq query(<book> T A <price unit="$"> N1 </price> </book> BL , price > N2) =
      query(BL, price > N2) if N1 <= N2 .
   cq query(<book> T A <price unit="$"> N1 </price> </book> BL , price > N2) =
      <book> T A <price unit="$"> N1 </price> </book> query(BL, price > N2)
        if N1 > N2 .
   cq query(<book> T A <price unit="$"> N1 </price> </book> , price > N2) = nil
        if N1 <= N2 .
   cq query(<book> T A <price unit="$"> N1 </price> </book> , price > N2) =
	<book> T A <price unit="$"> N1 </price> </book>
        if N1 > N2 .
endo

red query(doc1, price > 40) .

***> DTD for Book Store 2
obj BOOKSTORE2-DTD is
   pr QID .
   pr INT .
   pr STRING .
   sorts Document Book BookList Title Author Price FirstName LastName .
   subsort Book < BookList .
   op nil : -> BookList .
   op _ _ : BookList BookList -> BookList [ assoc idr: nil ].
   op <document> _ </document> : BookList -> Document .
   op <book> _ _ _ </book> : Title Author Price -> Book .
   op <title> _ </title> : String  -> Title .
   op <author> _ _ </author> : FirstName LastName -> Author .
   op <first-name> _ </first-name> : Id -> FirstName .
   op <last-name> _ </last-name> : Id -> LastName .
   op <price unit="yuan"> _ </price> : Int -> Price .
endo

***> XML for Book Store 2
obj BOOKSTORE2-XML is
   pr BOOKSTORE2-DTD .
   op doc2 : -> Document .
   eq doc2 = <document>
	       <book>
                   <title>  'Java 'and 'XML </title>
	           <author>
                       <first-name> 'Brett     </first-name>
                       <last-name> 'McLaughlin </last-name>
                   </author>
                   <price unit="yuan">  350 </price>
	       </book>
	       <book>
                   <title>  'Professional 'XML 'Databases  </title>
	           <author>
                       <first-name>  'Kevin </first-name>
                       <last-name> 'Williams </last-name>
                   </author>
                   <price unit="yuan">  530 </price>
	       </book>
	       <book>
                   <title>  'XML 'by 'Example   </title>
	           <author>
                       <first-name> 'Benoit </first-name>
                       <last-name> 'Marchal </last-name>
                   </author>
                   <price unit="yuan">  190 </price>
	       </book>
	     </document> .
endo

***> Query for Book Store2
obj QUERY-BOOKSTORE2 is
   pr BOOKSTORE2-XML .
   pr QUERY .
   op query : Document Query -> BookList .
   op query : BookList Query -> BookList .
   var BL : BookList .
   vars N N1 N2 : Int .
   var T : Title .
   var A : Author .
   var P : Price .
   eq query(<document> BL </document>, price > N) = query(BL, price > N) .
   cq query(<book> T A <price unit="yuan"> N1 </price> </book> BL ,
            price > N2) = query(BL, price > N2) if N1 <= N2 .
   cq query(<book> T A <price unit="yuan"> N1 </price> </book> BL ,
            price > N2) =
      <book> T A <price  unit="yuan"> N1 </price> </book> query(BL, price > N2)
            if N1 > N2 .
   cq query(<book> T A <price unit="yuan"> N1 </price> </book>, price > N2) =
            nil if N1 <= N2 .
   cq query(<book> T A <price unit="yuan"> N1 </price> </book>, price > N2) =
	<book> T A <price unit="yuan"> N1 </price> </book>
        if N1 > N2 .
endo

red query(doc2, price > 320) .

***> combined bookstore
obj MY-BOOKSTORE-DTD is
   pr QID .
   pr INT .
   pr STRING .
   sorts Document Book BookList Title Author Price FirstName LastName .
   subsort Book < BookList .
   op nil : -> BookList .
   op _ _ : BookList BookList -> BookList [ assoc idr: nil ].
   op <document> _ <document> : BookList -> Document .
   op <book> _ _ _ </book> : Title Author Price -> Book .
   op <title> _ </title> : String -> Title .
   op <author> _ _ </author> : FirstName LastName -> Author .
   op <firstname> _ </firstname> : Id -> FirstName .
   op <lastname> _ </lastname> : Id -> LastName .
   op <price unit="$"> _ </price> : Int -> Price .
endo

obj QUERY-MY-BOOKSTORE is
   pr MY-BOOKSTORE-DTD .
   pr QUERY-BOOKSTORE1 .
   pr QUERY-BOOKSTORE2 .
   op doc : -> Document.MY-BOOKSTORE-DTD  .
   op query : Document.MY-BOOKSTORE-DTD  Query ->
BookList.MY-BOOKSTORE-DTD .
   op f1 : BookList.BOOKSTORE1-DTD -> BookList.MY-BOOKSTORE-DTD .
   op f2 : BookList.BOOKSTORE2-DTD -> BookList.MY-BOOKSTORE-DTD .
   op q : Query -> Query .
   var Q : Query . var N : NzInt .
   var S : String .
   vars I1 I2 : Id .
   eq query(doc, Q) = f1(query(doc1, Q)) f2(query(doc2, q(Q))) .
   eq q(price > N) = price > (N * 8) .
   eq    f1(<book>
               <title> S </title>
               <author> I1 I2 </author>
               <price unit="$"> N </price>
            </book> )
      =  <book>
            <title> S </title>
            <author>
                <firstname> I1  </firstname>
                <lastname> I2 </lastname>
            </author>
            <price unit="$"> N </price>
         </book> .

   eq    f2(<book>
               <title> S </title>
               <author>
                   <first-name> I1  </first-name>
                   <last-name> I2 </last-name>
               </author>
               <price unit="yuan"> N </price>
            </book> )
      =  <book>
            <title> S </title>
            <author>
               <firstname> I1  </firstname>
               <lastname> I2 </lastname>
            </author>
            <price unit="$"> (N quo 8) </price>
         </book> .
endo

red query(doc, price > 50) .