Datalog docs

collects/datalog/scribblings/datalog.scrbl

@@ -3,18 +3,21 @@
           scribble/eval
           scribble/basic
           scribble/bnf
-          (for-label racket/base
-                     racket/contract
-                     "../main.rkt")
           "utils.rkt")
 
 @title[#:tag "top"]{@bold{Datalog}: Deductive database programming}
 @author[(author+email "Jay McCarthy" "jay@racket-lang.org")]
 
-This package contains a lightweight deductive database system. Queries and database updates are expressed
-using @link["http://en.wikipedia.org/wiki/Datalog"]{Datalog}---a declarative logic language in which each
+@link["http://en.wikipedia.org/wiki/Datalog"]{Datalog} is 
+@itemize[
+ @item{a declarative logic language in which each
 formula is a function-free Horn clause, and every variable
-in the head of a clause must appear in the body of the clause. The use of Datalog syntax and an implementation based
+in the head of a clause must appear in the body of the clause.}
+ @item{a lightweight deductive database system where queries and database updates are expressed
+       in the logic language.}
+]
+
+The use of Datalog syntax and an implementation based
 on tabling intermediate results ensures that all queries terminate.
 
 @table-of-contents[]
@@ -23,10 +26,6 @@ on tabling intermediate results ensures that all queries terminate.
 
 @defmodulelang[datalog]
 
-XXX Progress
-
-@subsection{Datalog Syntax}
-
 In Datalog input, whitespace characters are ignored except when they separate adjacent tokens or when they occur in strings.
 Comments are also considered to be whitespace. The character @litchar["%"] introduces a comment, which extends to the next line break.
 Comments do not occur inside strings.
@@ -70,17 +69,7 @@ END
 
 A program is a sequence of zero or more statements. A statement is an assertion, a retraction, or a query. An assertion is a clause followed by
 a period, and it adds the clause to the database if it is safe. A retraction is a clause followed by a tilde, and it removes the clause from
-the database. A query is a literal followed by a question mark. The effect of reading a Datalog program is to modify the database as directed
-by its statements, and then to return the literal designated as the query. If no query is specified, a reader returns a literal know to have no
-answers. The following is a program:
-
-@verbatim[#:indent 4 #<<END
-     edge(a, b). edge(b, c). edge(c, d). edge(d, a).
-     path(X, Y) :- edge(X, Y).
-     path(X, Y) :- edge(X, Z), path(Z, Y).
-     path(X, Y)?
-END
-]
+the database. A query is a literal followed by a question mark. 
 
 The following BNF describes the syntax of Datalog.
 
@@ -122,38 +111,66 @@ The following BNF describes the syntax of Datalog.
        (nonterm "STRING"))                
 ]
 
+The effect of running a Datalog program is to modify the database as directed
+by its statements, and then to return the literals designated by the query.
+
+The following is a program:
+
+@verbatim[#:indent 4 #<<END
+     #lang datalog
+     edge(a, b). edge(b, c). edge(c, d). edge(d, a).
+     path(X, Y) :- edge(X, Y).
+     path(X, Y) :- edge(X, Z), path(Z, Y).
+     path(X, Y)?
+END
+]
+
+Currently, REPL interaction is not supported.
+
 @section{Parenthetical Datalog Module Language}
+@(require (for-label datalog/sexp/lang))
 
 @defmodulelang[datalog/sexp]
 
-XXX Progress
+The semantics of this language is the same as the normal Datalog language, except it uses a @secref["parenstx"].
 
-@subsection{Parenthetical Datalog Syntax}
+Literals are represented as S-expressions with identifiers for constant symbols, strings for constant strings, and @racket[,id] for variable symbols.
 
-@racketgrammar*[
- #:literals (:- ! ~ ? unquote)
- [program (begin statement ...)]
- [statement assertion
-            retraction
-            query]
- [assertion (! clause)]
- [retraction (~ clause)]
- [query (? literal)]
- [clause (:- literal literal ...)
-         literal]
- [literal (datum term ...)]
- [term variable
-       constant]
- [variable ,symbol]
- [constant datum]
- [datum symbol
-        string]]
+@racket[unquote], top-level identifiers, and strings are not otherwise allowed in the program.
+
+The following is a program:
+@racketmod[datalog/sexp
+           
+(! (edge a b))
+(! (edge b c))
+(! (edge c d))
+(! (edge d a))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Y)))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Z)
+       (path ,Z ,Y)))
+(? (path ,X ,Y))]
+
+@subsection[#:tag "parenstx"]{Parenthetical Syntax}
+
+@defmodule[datalog/sexp/lang]
+
+@defform[(! clause)]{ Asserts the clause. }
+@defform[(~ clause)]{ Retracts the literal. }
+@defform[(? literal)]{ Queries the literal and prints the result literals. }
+
+@defform[(:- literal literal ...)]{ A conditional clause. }
+
+@defform[(= term term)]{ An equality literal. }
+
+@defform[(unquote symbol)]{ A variable symbol. }
 
 @include-section["racket.scrbl"]
 
 @section{Acknowledgments}
 
-This package is structurally based on Dave Herman's @racketmodname[(planet dherman/javascript)] library and
+This package was once structurally based on Dave Herman's @racketmodname[(planet dherman/javascript)] library and
 John Ramsdell's @link["http://www.ccs.neu.edu/home/ramsdell/tools/datalog/datalog.html"]{Datalog library}. 
 
 The package uses the tabled logic programming algorithm described in

collects/datalog/scribblings/racket.scrbl

@@ -12,6 +12,8 @@
 
 @defmodule[datalog]
 
+The Datalog database can be directly used by Racket programs through this API.
+
 @examples[#:eval the-eval
           (define example-program
             #<<END
@@ -588,6 +590,13 @@ This library provides facilities for evaluating Datalog. It can be required via:
     (open-input-string
      "path(X, Y) :- edge(X, a).")))]
 }
+
+@defproc[(eval-top-level-statement [s statement/c])
+         void]{
+ Evaluates @racket[s] using @racket[(current-theory)] as the @tech{theory}, printing query answers if @racket[s] is a query.
+           
+ This will raise a syntax error if given an @racket[assertion] of a @racket[clause] that is not a @racket[safe-clause?].
+ }
               
 @defproc[(eval-statement [s statement/c])
          (or/c void (listof literal?))]{

collects/datalog/sexp/lang.rkt

@@ -1,23 +1,31 @@
 #lang racket
 (require (for-syntax syntax/parse)
+         racket/stxparam
          "../eval.rkt"
          "../ast.rkt")
 
-(define-syntax (top stx)
+(define-syntax-parameter top
+  (λ (stx) (raise-syntax-error '#%top "undefined identifier" stx)))
+(define-syntax-parameter unquote
+  (λ (stx) (raise-syntax-error 'unquote "only allowed inside literals" stx)))
+(define-syntax-parameter datum
+  (λ (stx) (raise-syntax-error '#%datum "only allowed inside literals" stx)))
+
+(define-syntax (literal-top stx)
   (syntax-parse 
    stx
    [(_ . sym:id)
     (quasisyntax/loc stx
       (constant #'#,stx 'sym))]))
 
-(define-syntax (unquote stx)
+(define-syntax (literal-unquote stx)
   (syntax-parse 
    stx
    [(_ sym:id)
     (quasisyntax/loc stx
       (variable #'#,stx 'sym))]))
 
-(define-syntax (datum stx)
+(define-syntax (literal-datum stx)
   (syntax-parse 
    stx
    [(_ . sym:str)
@@ -32,10 +40,17 @@
       (literal #'#,stx 'sym empty))]
    [(_ (sym:id e ...))
     (quasisyntax/loc stx
-      (literal #'#,stx 'sym (list e ...)))]))
+      (literal #'#,stx 'sym 
+               (syntax-parameterize ([top (make-rename-transformer #'literal-top)]
+                                     [datum (make-rename-transformer #'literal-datum)]
+                                     [unquote (make-rename-transformer #'literal-unquote)])
+                                    (list e ...))))]))
 
 (define-syntax (->simple-clause stx)
-  (syntax-case stx ()
+  (syntax-case stx (:-)
+    [(_ (:- . r))
+     (quasisyntax/loc stx
+       (:- . r))]
     [(_ e)
      (quasisyntax/loc stx
        (clause #'#,stx (->literal e) empty))]))
@@ -44,10 +59,8 @@
   (syntax-case stx ()
     [(_ head body ...)
      (quasisyntax/loc stx
-       (eval-top-level-statement 
-        (assertion #'#,stx 
-                   (clause #'#,stx (->literal head) 
-                           (list (->literal body) ...)))))]))
+       (clause #'#,stx (->literal head) 
+               (list (->literal body) ...)))]))
 
 (define-syntax-rule (define-paren-stx op struct)
   (define-syntax (op stx)
@@ -65,12 +78,14 @@
      (quasisyntax/loc stx
        (eval-top-level-statement (query #'#,stx (->literal c))))]))
 
+(define-syntax (= stx)
+  (quasisyntax/loc stx
+    (constant #'#,stx '=)))
+
 (provide (rename-out [top #%top]
-                     [datum #%datum]
-                     #;[module-begin #%module-begin]
-                     #;[top-interaction #%top-interaction])
-         
+                     [datum #%datum])
+         #%top-interaction
          #%module-begin
          ! ~ ?
-         :-
+         :- =
          unquote)

collects/datalog/tests/paren-examples/ancestor.rkt

@@ -1,11 +1,11 @@
 #lang datalog/sexp
 ; Equality test
-(:- (ancestor ,A ,B)
-    (parent ,A ,B))
-(:- (ancestor ,A ,B)
-    (parent ,A ,C)
-    (= D C) ; Unification required
-    (ancestor ,D ,B))
+(! (:- (ancestor ,A ,B)
+       (parent ,A ,B)))
+(! (:- (ancestor ,A ,B)
+       (parent ,A ,C)
+       (= D C) ; Unification required
+       (ancestor ,D ,B)))
 (! (parent john douglas))
 (! (parent bob john))
 (! (parent ebbon bob))

collects/datalog/tests/paren-examples/bidipath.rkt

@@ -4,12 +4,12 @@
 (! (edge b c))
 (! (edge c d))
 (! (edge d a))
-(:- (path ,X ,Y)
-    (edge ,X ,Y))
-(:- (path ,X ,Y)
-    (edge ,X ,Z)
-    (path ,Z ,Y))
-(:- (path ,X ,Y)
-    (path ,X ,Z)
-    (edge ,Z ,Y))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Y)))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Z)
+       (path ,Z ,Y)))
+(! (:- (path ,X ,Y)
+       (path ,X ,Z)
+       (edge ,Z ,Y)))
 (? (path ,X ,Y))

collects/datalog/tests/paren-examples/laps.rkt

@@ -2,12 +2,12 @@
 ; Laps Test
 (! (contains ca store rams_couch rams))
 (! (contains rams fetch rams_couch will))
-(:- (contains ca fetch ,Name ,Watcher)
-    (contains ca store ,Name ,Owner)
-    (contains ,Owner fetch ,Name ,Watcher))
+(! (:- (contains ca fetch ,Name ,Watcher)
+       (contains ca store ,Name ,Owner)
+       (contains ,Owner fetch ,Name ,Watcher)))
 (! (trusted ca))
-(:- (permit ,User ,Priv ,Name)
-    (contains ,Auth ,Priv ,Name ,User)
-    (trusted ,Auth))
+(! (:- (permit ,User ,Priv ,Name)
+       (contains ,Auth ,Priv ,Name ,User)
+       (trusted ,Auth)))
 (? (permit ,User ,Priv ,Name))
 

collects/datalog/tests/paren-examples/path.rkt

@@ -4,9 +4,9 @@
 (! (edge b c))
 (! (edge c d))
 (! (edge d a))
-(:- (path ,X ,Y)
-    (edge ,X ,Y))
-(:- (path ,X ,Y)
-    (edge ,X ,Z)
-    (path ,Z ,Y))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Y)))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Z)
+       (path ,Z ,Y)))
 (? (path ,X ,Y))

collects/datalog/tests/paren-examples/pq.rkt

@@ -1,8 +1,8 @@
 #lang datalog/sexp
 ; p q test from Chen & Warren
-(:- (q ,X)
-    (p ,X))
+(! (:- (q ,X)
+       (p ,X)))
 (! (q a))
-(:- (p ,X)
-    (q ,X))
+(! (:- (p ,X)
+       (q ,X)))
 (? (q ,X))

collects/datalog/tests/paren-examples/revpath.rkt

@@ -4,9 +4,9 @@
 (! (edge b c))
 (! (edge c d))
 (! (edge d a))
-(:- (path ,X ,Y)
-    (edge ,X ,Y))
-(:- (path ,X ,Y)
-    (path ,X ,Z)
-    (edge ,Z ,Y))
+(! (:- (path ,X ,Y)
+       (edge ,X ,Y)))
+(! (:- (path ,X ,Y)
+       (path ,X ,Z)
+       (edge ,Z ,Y)))
 (? (path ,X ,Y))

collects/datalog/tests/paren-examples/says.rkt

@@ -1,7 +1,7 @@
 #lang datalog/sexp
 (! (tpme tpme1))
 (! (ms m1 "TPME" tpme1 ek tp))
-(:- (says ,TPME ,M)
-    (tpme ,TPME)
-    (ms ,M "TPME" ,TPME ,A ,B))
+(! (:- (says ,TPME ,M)
+       (tpme ,TPME)
+       (ms ,M "TPME" ,TPME ,A ,B)))
 (? (says ,A ,B))

collects/datalog/tests/paren-examples/true.rkt

@@ -1,3 +1,3 @@
 #lang datalog/sexp
 (! true)
-(? true)
+(? true)

collects/datalog/tests/paren-examples/tutorial.rkt

@@ -12,11 +12,11 @@
 
 (? (parent ,A ,A))
 
-(:- (ancestor ,A ,B)
-    (parent ,A ,B))
-(:- (ancestor ,A ,B)
-    (parent ,A ,C)
-    (ancestor ,C ,B))
+(! (:- (ancestor ,A ,B)
+       (parent ,A ,B)))
+(! (:- (ancestor ,A ,B)
+       (parent ,A ,C)
+       (ancestor ,C ,B)))
 (? (ancestor ,A ,B))
 
 (? (ancestor ,X john))