diff --git a/collects/datalog/ast.rkt b/collects/datalog/ast.rkt
index ed41f663ea..41052706aa 100644
--- a/collects/datalog/ast.rkt
+++ b/collects/datalog/ast.rkt
@@ -15,9 +15,9 @@
 (define-struct variable (srcloc sym) #:prefab)  
 (define (variable-equal? v1 v2)
   (eq? (variable-sym v1) (variable-sym v2)))
-(define-struct constant (srcloc datum) #:prefab)
+(define-struct constant (srcloc value) #:prefab)
 (define (constant-equal? v1 v2)
-  (datum-equal? (constant-datum v1) (constant-datum v2)))
+  (equal? (constant-value v1) (constant-value v2)))
 
 (define term/c (or/c variable? constant?))
 (define (term-equal? t1 t2)
@@ -29,15 +29,31 @@
     [else
      #f]))
 
+(define (terms-equal? t1 t2)
+  (and (= (length t1)
+          (length t2))
+       (andmap term-equal? t1 t2)))
+
 (define-struct literal (srcloc predicate terms) #:prefab)
 (define (literal-equal? l1 l2)
   (and (datum-equal? (literal-predicate l1)
                      (literal-predicate l2))
-       (= (length (literal-terms l1))
-          (length (literal-terms l2)))
-       (andmap term-equal?
-               (literal-terms l1)
-               (literal-terms l2))))
+       (terms-equal? (literal-terms l1) (literal-terms l2))))
+
+(define-struct external (srcloc predicate-sym predicate arg-terms ans-terms) #:prefab)
+(define (external-equal? e1 e2)
+  (match-define (external _1 _s1 p1 ar1 an1) e1)
+  (match-define (external _2 _s2 p2 ar2 an2) e2)
+  (and (equal? p1 p2)
+       (terms-equal? ar1 ar2)
+       (terms-equal? an1 an2)))
+
+(define question/c (or/c literal? external?))
+(define (question-equal? q1 q2)
+  (or (and (literal? q1) (literal? q2)
+           (literal-equal? q1 q2))
+      (and (external? q1) (external? q2)
+           (external-equal? q1 q2))))
 
 (define-struct clause (srcloc head body) #:prefab)
 (define (clause-equal? c1 c2)
@@ -45,13 +61,13 @@
                        (clause-head c2))
        (= (length (clause-body c1))
           (length (clause-body c2)))
-       (andmap literal-equal?
+       (andmap question-equal?
                (clause-body c1)
                (clause-body c2))))
 
 (define-struct assertion (srcloc clause) #:prefab)
 (define-struct retraction (srcloc clause) #:prefab)
-(define-struct query (srcloc literal) #:prefab)
+(define-struct query (srcloc question) #:prefab)
 
 (define statement/c (or/c assertion? retraction? query?))
 (define program/c (listof statement/c))
@@ -64,7 +80,7 @@
                    [sym symbol?])]
  [variable-equal? (variable? variable? . -> . boolean?)]
  [struct constant ([srcloc srcloc/c]
-                   [datum datum/c])]
+                   [value any/c])]
  [constant-equal? (constant? constant? . -> . boolean?)]
  [term/c contract?]
  [term-equal? (term/c term/c . -> . boolean?)]
@@ -72,15 +88,23 @@
                   [predicate datum/c]
                   [terms (listof term/c)])]
  [literal-equal? (literal? literal? . -> . boolean?)]
+ [struct external ([srcloc srcloc/c]
+                   [predicate-sym symbol?]
+                   [predicate procedure?]
+                   [arg-terms (listof term/c)]
+                   [ans-terms (listof term/c)])]
+ [external-equal? (external? external? . -> . boolean?)]
+ [question/c contract?]
+ [question-equal? (question/c question/c . -> . boolean?)]
  [struct clause ([srcloc srcloc/c]
                  [head literal?]
-                 [body (listof literal?)])]
+                 [body (listof question/c)])]
  [clause-equal? (clause? clause? . -> . boolean?)]
  [struct assertion ([srcloc srcloc/c]
                     [clause clause?])]
  [struct retraction ([srcloc srcloc/c]
                      [clause clause?])]
  [struct query ([srcloc srcloc/c]
-                [literal literal?])]
+                [question question/c])]
  [statement/c contract?]
  [program/c contract?])
diff --git a/collects/datalog/eval.rkt b/collects/datalog/eval.rkt
index 82f6e67d2a..ac1e51f5fa 100644
--- a/collects/datalog/eval.rkt
+++ b/collects/datalog/eval.rkt
@@ -14,9 +14,9 @@
                             "Unsafe clause in assertion"
                             (datum->syntax #f (format-statement s) (assertion-srcloc s))))))
 
-(define (print-literals ls)
+(define (print-questions ls)
   (displayln 
-   (format-literals ls)))
+   (format-questions ls)))
 
 (define (eval-program p)
   (for-each eval-top-level-statement p))
@@ -24,7 +24,7 @@
 (define (eval-top-level-statement s)
   (define v (eval-statement s))
   (unless (void? v)
-    (print-literals v)))
+    (print-questions v)))
 
 (define (eval-statement s)
   (cond
@@ -33,7 +33,7 @@
     [(retraction? s)
      (retract! (current-theory) (retraction-clause s))]
     [(query? s)
-     (prove (current-theory) (query-literal s))]))
+     (prove (current-theory) (query-question s))]))
 
 (define (eval-program/fresh p)
   (let loop ([thy (make-immutable-theory)]
@@ -48,14 +48,14 @@
              [(retraction? s)
               (retract thy (retraction-clause s))]
              [(query? s)
-              (print-literals (prove thy (query-literal s)))
+              (print-questions (prove thy (query-question s)))
               thy])
            (rest p))))))
 
 (provide/contract
  [current-theory (parameter/c mutable-theory/c)]
- [print-literals ((listof literal?) . -> . void)]
+ [print-questions ((listof question/c) . -> . void)]
  [eval-program (program/c . -> . void)]
  [eval-top-level-statement (statement/c . -> . void)]
- [eval-statement (statement/c . -> . (or/c void (listof literal?)))]
+ [eval-statement (statement/c . -> . (or/c void (listof question/c)))]
  [eval-program/fresh (program/c . -> . immutable-theory/c)])
\ No newline at end of file
diff --git a/collects/datalog/pretty.rkt b/collects/datalog/pretty.rkt
index e58d7d9f8b..39f92f6418 100644
--- a/collects/datalog/pretty.rkt
+++ b/collects/datalog/pretty.rkt
@@ -4,19 +4,19 @@
 
 (define (format-datum s)
   (cond
-    [(string? s)
-     (text (format "~S" s))]
     [(symbol? s)
-     (text (symbol->string s))]))
+     (text (symbol->string s))]
+    [else
+     (text (format "~S" s))]))
 (define (format-variable v)
   (format-datum (variable-sym v)))
 (define (format-constant c)
-  (format-datum (constant-datum c)))
-(define (format-term t)
-  (cond
-    [(variable? t)
+  (format-datum (constant-value c)))
+(define format-term 
+  (match-lambda
+    [(? variable? t)
      (format-variable t)]
-    [(constant? t)
+    [(? constant? t)
      (format-constant t)]))
 (define (format-literal l)
   (match l
@@ -29,10 +29,27 @@
                lparen
                (v-concat/s (apply-infix ", " (map format-term terms)))
                rparen)]))
-(define (format-literals ls)
+(define format-external
+  (match-lambda
+    [(external _ pred-sym pred args anss)
+     (h-append (format-datum pred-sym)
+               lparen
+               (v-concat/s (apply-infix ", " (map format-term args)))
+               rparen
+               (text " = ")
+               lparen
+               (v-concat/s (apply-infix ", " (map format-term anss)))
+               rparen)]))
+(define format-question
+  (match-lambda
+    [(? literal? l)
+     (format-literal l)]
+    [(? external? e)
+     (format-external e)]))
+(define (format-questions ls)
   (v-concat
    (append (map (lambda (l)
-                  (format-assertion (make-assertion #f (make-clause #f l (list)))))
+                  (h-append (format-question l) dot))
                 ls)
            (list line))))
 (define (format-clause c)
@@ -49,7 +66,7 @@
   (h-append (format-clause (retraction-clause r))
             (char #\~)))
 (define (format-query q)
-  (h-append (format-literal (query-literal q))
+  (h-append (format-question (query-question q))
             (char #\?)))
 
 (define (format-statement s)
@@ -66,7 +83,7 @@
  [format-constant (constant? . -> . doc?)]
  [format-term (term/c . -> . doc?)]
  [format-literal (literal? . -> . doc?)]
- [format-literals ((listof literal?) . -> . doc?)]
+ [format-questions ((listof question/c) . -> . doc?)]
  [format-clause (clause? . -> . doc?)]
  [format-assertion (assertion? . -> . doc?)]
  [format-retraction (retraction? . -> . doc?)]
diff --git a/collects/datalog/private/subst.rkt b/collects/datalog/private/subst.rkt
index 3ec35811fc..646e66dc76 100644
--- a/collects/datalog/private/subst.rkt
+++ b/collects/datalog/private/subst.rkt
@@ -9,32 +9,52 @@
     [_
      t]))
 
+(define (subst-terms env ts)
+  (map (curry subst-term env) ts))
+
 (define (subst-literal env lit)
-  (make-literal (literal-srcloc lit)
-                (literal-predicate lit)
-                (map (lambda (t) (subst-term env t))
-                     (literal-terms lit))))
+  (struct-copy 
+   literal lit
+   [terms 
+    (subst-terms env (literal-terms lit))]))
+
+(define (subst-external env ext)
+  (struct-copy 
+   external ext
+   [arg-terms 
+    (subst-terms env (external-arg-terms ext))]
+   [ans-terms 
+    (subst-terms env (external-ans-terms ext))]))
+
+(define (subst-question env q)
+  (match q
+    [(? literal?) (subst-literal env q)]
+    [(? external?) (subst-external env q)]))
 
 (define (subst-clause env c)
-  (make-clause (clause-srcloc c)
-               (subst-literal env (clause-head c))
-               (map (lambda (l) (subst-literal env l))
-                    (clause-body c))))
+  (clause (clause-srcloc c)
+          (subst-literal env (clause-head c))
+          (map (curry subst-question env)
+               (clause-body c))))
 
-(define (shuffle env lit)
-  (match lit
-    [(struct literal (_ pred terms))
-     (let loop ([env env]
-                [terms terms])
-       (match terms
-         [(list) 
-          env]
-         [(list-rest (struct constant (_ value)) terms)
-          (loop env terms)]
-         [(list-rest (struct variable (srcloc var)) terms)
-          (if (lookup env var)
-              (loop env terms)
-              (loop (extend env var (make-variable srcloc (gensym var))) terms))]))]))
+(define (shuffle-terms env terms)
+  (match terms
+    [(list) 
+     env]
+    [(list-rest (constant _ value) terms)
+     (shuffle-terms env terms)]
+    [(list-rest (variable srcloc var) terms)
+     (if (lookup env var)
+         (shuffle-terms env terms)
+         (shuffle-terms (extend env var (make-variable srcloc (gensym var)))
+                        terms))]))
+
+(define (shuffle env q)
+  (match q
+    [(external _ _ pred arg-terms ans-terms)
+     (shuffle-terms env (append arg-terms ans-terms))]
+    [(literal _ pred terms)
+     (shuffle-terms env terms)]))
 
 (define (rename-clause c)
   (define env
@@ -44,11 +64,12 @@
            (clause-body c)))  
   (subst-clause env c))  
 
-(define (rename-literal lit)
-  (subst-literal (shuffle (empty-env) lit) lit))
+(define (rename-question q)
+  (subst-question (shuffle (empty-env) q) q))
 
 (provide/contract
+ [subst-terms (env/c (listof term/c) . -> . (listof term/c))]
  [subst-term (env/c term/c . -> . term/c)]
  [subst-clause (env/c clause? . -> . clause?)]
  [rename-clause (clause? . -> . clause?)]
- [rename-literal (literal? . -> . literal?)])
\ No newline at end of file
+ [rename-question (question/c . -> . question/c)])
\ No newline at end of file
diff --git a/collects/datalog/private/unify.rkt b/collects/datalog/private/unify.rkt
index 8943e27ec6..fabbdf2c6b 100644
--- a/collects/datalog/private/unify.rkt
+++ b/collects/datalog/private/unify.rkt
@@ -38,12 +38,22 @@
             [env (unify-terms env (rest ts1) (rest ts2))]))))      
 
 (define (unify l1 l2)
-  (and (datum-equal? (literal-predicate l1)
-                     (literal-predicate l2))
-       (unify-terms (empty-env)
-                    (literal-terms l1)
-                    (literal-terms l2))))
+  (or (and (literal? l1) (literal? l2)
+           (datum-equal? (literal-predicate l1)
+                         (literal-predicate l2))
+           (unify-terms (empty-env)
+                        (literal-terms l1)
+                        (literal-terms l2)))
+      (and (external? l1) (external? l2)
+           (equal? (external-predicate l1)
+                   (external-predicate l2))
+           (unify-terms (empty-env)
+                        (append (external-arg-terms l1)
+                                (external-ans-terms l1))
+                        (append (external-arg-terms l2)
+                                (external-ans-terms l2))))))
 
 (provide/contract
- [unify (literal? literal? . -> . (or/c false/c env/c))]
+ [unify (question/c question/c . -> . (or/c false/c env/c))]
+ [unify-terms (env/c (listof term/c) (listof term/c) . -> . (or/c false/c env/c))]
  [unify-term (env/c term/c term/c . -> . (or/c false/c env/c))])
\ No newline at end of file
diff --git a/collects/datalog/private/variant.rkt b/collects/datalog/private/variant.rkt
index e28981d46e..76b77e4c46 100644
--- a/collects/datalog/private/variant.rkt
+++ b/collects/datalog/private/variant.rkt
@@ -35,13 +35,25 @@
     [_ #f]))
 
 (define (variant? l1 l2)
-  (and 
-   (datum-equal? (literal-predicate l1)
-                 (literal-predicate l2))
-   (variant-terms 
-    (empty-env) (empty-env)
-    (literal-terms l1)
-    (literal-terms l2))))
+  (or 
+   (and (literal? l1) (literal? l2)
+        (datum-equal? (literal-predicate l1)
+                      (literal-predicate l2))
+        (variant-terms 
+         (empty-env) (empty-env)
+         (literal-terms l1)
+         (literal-terms l2)))
+   (and (external? l1) (external? l2)
+        (equal? (external-predicate l1)
+                (external-predicate l2))
+        (variant-terms 
+         (empty-env) (empty-env)
+         (external-arg-terms l1)
+         (external-arg-terms l2))
+        (variant-terms 
+         (empty-env) (empty-env)
+         (external-ans-terms l1)
+         (external-ans-terms l2)))))
 
 (define (mem-literal lit ls)
   (ormap (lambda (l) (variant? lit l)) ls))
@@ -52,11 +64,21 @@
     [(variable? t)
      101]
     [(constant? t)
-     (recur-hash (constant-datum t))]))
-(define ((mk-literal-hash recur-hash) l)
-  (let loop ([code (recur-hash (literal-predicate l))]
+     (recur-hash (constant-value t))]))
+(define ((mk-literal-hash recur-hash) q)
+  (define-values
+    (code terms)
+    (match q
+      [(? literal? l)
+       (values (recur-hash (literal-predicate l))
+               (literal-terms l))]
+      [(? external? e)
+       (values (recur-hash (external-predicate e))
+               (append (external-arg-terms e)
+                       (external-ans-terms e)))]))
+  (let loop ([code code]
              [i 0]
-             [terms (literal-terms l)])
+             [terms terms])
     (if (empty? terms)
         code
         (loop (+ code (term-hash (first terms) recur-hash) (* i -7))
@@ -78,6 +100,6 @@
 (provide/contract
  [literal-tbl/c contract?]
  [make-literal-tbl (-> literal-tbl/c)]
- [literal-tbl-find (literal-tbl/c literal? . -> . (or/c false/c any/c))]
- [literal-tbl-replace! (literal-tbl/c literal? any/c . -> . void)]
- [mem-literal (literal? (listof literal?) . -> . boolean?)])
\ No newline at end of file
+ [literal-tbl-find (literal-tbl/c question/c . -> . (or/c false/c any/c))]
+ [literal-tbl-replace! (literal-tbl/c question/c any/c . -> . void)]
+ [mem-literal (question/c (listof question/c) . -> . boolean?)])
\ No newline at end of file
diff --git a/collects/datalog/runtime.rkt b/collects/datalog/runtime.rkt
index a7a0feaf52..f0715fdb25 100644
--- a/collects/datalog/runtime.rkt
+++ b/collects/datalog/runtime.rkt
@@ -11,7 +11,12 @@
   (andmap (lambda (v)
             (ormap (lambda (l)
                      (ormap (lambda (t) (term-equal? t v))
-                            (literal-terms l)))
+                            (cond
+                              [(literal? l)
+                               (literal-terms l)]
+                              [(external? l)
+                               (append (external-arg-terms l)
+                                       (external-ans-terms l))])))
                    (clause-body c)))
           head-vars))
 
@@ -52,20 +57,20 @@
   (hash-ref thy (literal-key lit) empty))
 
 (define-struct subgoal 
-  (literal 
+  (question 
    [facts #:mutable]
    [waiters #:mutable]))
 
-(define (resolve c lit)
+(define (resolve c q)
   (define body (clause-body c))
   (and (not (empty? body))
        (cond
-         [(unify (first body) (rename-literal lit))
+         [(unify (first body) (rename-question q))
           => (lambda (env)
                (subst-clause env (make-clause (clause-srcloc c) (clause-head c) (rest body))))]
          [else #f])))
 
-(define (prove thy lit)
+(define (prove thy q)
   (define subgoals (make-literal-tbl))
   (define (fact! sg lit)
     (unless (mem-literal lit (subgoal-facts sg))
@@ -100,12 +105,25 @@
        (define renamed (rename-clause clause))
        (define selected (clause-head renamed))
        (cond
-         [(unify (subgoal-literal sg) selected)
+         [(unify (subgoal-question sg) selected)
           => (lambda (env)
                (add-clause! sg (subst-clause env renamed)))]))
-     (get thy (subgoal-literal sg))))
+     (get thy (subgoal-question sg))))
   (define (search! sg)
-    (match (subgoal-literal sg)
+    (match (subgoal-question sg)
+      [(external srcloc pred-sym pred args anss)
+       (and (andmap constant? args)
+            (call-with-values 
+             (λ ()
+               (apply pred (map constant-value args)))
+             (λ resolved-vals
+               (define resolved-anss
+                 (map (curry constant #f)
+                      resolved-vals))
+               (cond
+                 [(unify-terms (empty-env) anss resolved-anss)
+                  => (λ (env)
+                       (fact! sg (external srcloc pred-sym pred args (subst-terms env anss))))]))))]
       [(struct literal (srcloc '= (list a b)))
        (define (equal-test a b)
          (when (term-equal? a b)
@@ -116,8 +134,8 @@
          [else (equal-test a b)])]
       [_
        (search-theory! sg)]))
-  (define sg (make-subgoal lit empty empty))
-  (literal-tbl-replace! subgoals lit sg)
+  (define sg (make-subgoal q empty empty))
+  (literal-tbl-replace! subgoals q sg)
   (search! sg)
   (subgoal-facts sg))
 
@@ -133,4 +151,4 @@
  [retract (immutable-theory/c clause? . -> . immutable-theory/c)]
  [assume! (mutable-theory/c safe-clause? . -> . void)]
  [retract! (mutable-theory/c clause? . -> . void)]
- [prove (theory/c literal? . -> . (listof literal?))])
\ No newline at end of file
+ [prove (theory/c question/c . -> . (listof question/c))])
\ No newline at end of file
diff --git a/collects/datalog/scribblings/datalog.scrbl b/collects/datalog/scribblings/datalog.scrbl
index 367feb9a9d..cef43910e1 100644
--- a/collects/datalog/scribblings/datalog.scrbl
+++ b/collects/datalog/scribblings/datalog.scrbl
@@ -130,13 +130,14 @@ The Datalog REPL accepts new statements that are executed as if they were in the
 @include-section["tutorial.scrbl"]
 
 @section{Parenthetical Datalog Module Language}
-@(require (for-label datalog))
+@(require (for-label datalog
+                     racket))
 
 @defmodulelang[datalog/sexp]
 
-The semantics of this language is the same as the normal Datalog language, except it uses a parenthetical syntax.
+The semantics of this language is the same as the normal Datalog language, except it uses the parenthetical syntax described in @secref{interop}.
 
-Literals are represented as S-expressions with non-capitalized identifiers for constant symbols, strings for constant strings, and capitalized identifiers for variable symbols. Top-level identifiers and strings are not otherwise allowed in the program.
+All identifiers in @racketmodname[racket/base] are available for use as predicate symbols or constant values. Top-level identifiers and datums are not otherwise allowed in the program. The program may contain @racket[require] expressions.
 
 The following is a program:
 @racketmod[datalog/sexp
@@ -152,7 +153,13 @@ The following is a program:
        (path Z Y)))
 (? (path X Y))]
 
-The Parenthetical Datalog REPL accepts new statements that are executed as if they were in the original program text.
+This is also a program:
+@racketmod[datalog/sexp
+(require racket/math)
+
+(? (sqr 4 :- X))]
+
+The Parenthetical Datalog REPL accepts new statements that are executed as if they were in the original program text, except @racket[require] is not allowed.
 
 @include-section["racket.scrbl"]
 
diff --git a/collects/datalog/scribblings/racket.scrbl b/collects/datalog/scribblings/racket.scrbl
index 195a7a1c5f..57e1ea3878 100644
--- a/collects/datalog/scribblings/racket.scrbl
+++ b/collects/datalog/scribblings/racket.scrbl
@@ -8,7 +8,7 @@
                      "../main.rkt")
           "utils.rkt")
 
-@title{Racket Interoperability}
+@title[#:tag "interop"]{Racket Interoperability}
 
 @defmodule[datalog]
 
@@ -45,7 +45,10 @@ The Datalog database can be directly used by Racket programs through this API.
  
           (let ([x 'joseph2])
             (datalog family
-                     (? (parent x X))))]
+                     (? (parent x X))))
+                                       
+          (datalog family
+                   (? (add1 1 :- X)))]
 
 @defthing[mutable-theory/c contract?]{ A contract for Datalog theories. }
 
@@ -58,11 +61,18 @@ The Datalog database can be directly used by Racket programs through this API.
 @defform[(datalog! thy-expr
                   stmt ...)
          #:contracts ([thy-expr mutable-theory/c])]{ Executes the statements on the theory given by @racket[thy-expr]. Prints the answers to every query in the list of statements. Returns @racket[(void)]. }     
-                                                   
-Literals are represented as S-expressions with non-capitalized identifiers for constant symbols, strings for constant strings, and capitalized identifiers for variable symbols. Bound identifiers are treated as constants; they must evaluate to either a symbol or string. 
+              
+Statements are either assertions, retractions, or queries.
 
 @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. }
\ No newline at end of file
+@defform[(:- literal question ...)]{ A conditional clause. }
+
+@defform[(? question)]{ Queries the literal and prints the result literals. }
+                                                   
+Questions are either literals or external queries.
+Literals are represented as @racket[identifier] or @racket[(identifier term ...)].
+Questions are represented as @racket[(identifier term ... :- term ...)], where @racket[identifier] is bound to a procedure that when given the first set of terms as arguments returns the second set of terms as values.
+A term is either a non-capitalized identifiers for a constant symbol, a Racket datum for a constant datum, or a capitalized identifier for a variable symbol. Bound identifiers in terms are treated as datums. 
+
diff --git a/collects/datalog/sexp/lang.rkt b/collects/datalog/sexp/lang.rkt
index addccfbd54..4a613740ed 100644
--- a/collects/datalog/sexp/lang.rkt
+++ b/collects/datalog/sexp/lang.rkt
@@ -1,15 +1,36 @@
-#lang racket
-(require (for-syntax syntax/parse)
+#lang racket/base
+(require (for-syntax syntax/parse
+                     racket/list
+                     racket/base)
          datalog/stx
          datalog/runtime)
 
 (define lang-theory (make-theory))
 
-(define-syntax module-begin
-  (syntax-rules ()
-    [(_ stmt ...)
-     (#%module-begin 
-      (datalog! lang-theory stmt ...))]))
+(define-for-syntax (partition-requires es)
+  (define-values (rs stmts)
+    (partition 
+     (λ (e-stx)
+       (syntax-parse
+        e-stx
+        #:literals (require)
+        [(require . r)
+         #t]
+        [_
+         #f]))
+     (syntax->list es)))
+  (list rs stmts))
+
+(define-syntax (module-begin stx)
+  (syntax-case stx ()
+    [(_ . es)
+     (with-syntax ([((requires ...)
+                     (stmt ...))
+                    (partition-requires #'es)])
+       (syntax/loc stx
+         (#%module-begin 
+          requires ...
+          (datalog! lang-theory stmt ...))))]))
 
 (define-syntax top-interaction
   (syntax-rules ()
@@ -18,4 +39,7 @@
 
 (provide (rename-out [top-interaction #%top-interaction]
                      [module-begin #%module-begin])
+         (except-out (all-from-out racket/base)
+                     #%top-interaction
+                     #%module-begin)
          ! ~ ? :-)
\ No newline at end of file
diff --git a/collects/datalog/stx.rkt b/collects/datalog/stx.rkt
index 9cff0b97f3..fdff1396e3 100644
--- a/collects/datalog/stx.rkt
+++ b/collects/datalog/stx.rkt
@@ -21,6 +21,10 @@
 
 (define literal->sexp
   (match-lambda
+    [(external _ pred-sym _ args anss)
+     `(,pred-sym ,@(map term->datum args)
+                 :-
+                 ,@(map term->datum anss))]
     [(literal _ pred ts)
      (list* pred (map term->datum ts))]))
 
@@ -49,57 +53,63 @@
   (syntax-parse 
    stx
    #:literals (! ~ ?)
-   [(_ (! c))
-    (quasisyntax/loc stx
-      (assertion #'#,stx (datalog-clause c)))]
-   [(_ (~ c))
-    (quasisyntax/loc stx
-      (retraction #'#,stx (datalog-clause c)))]
-   [(_ (? l))
-    (quasisyntax/loc stx
-      (query #'#,stx (datalog-literal l)))]))
+   [(_ (~and tstx (! c)))
+    (quasisyntax/loc #'tstx
+      (assertion #'#,#'tstx (datalog-clause c)))]
+   [(_ (~and tstx (~ c)))
+    (quasisyntax/loc #'tstx
+      (retraction #'#,#'tstx (datalog-clause c)))]
+   [(_ (~and tstx (? l)))
+    (quasisyntax/loc #'tstx
+      (query #'#,#'tstx (datalog-literal l)))]))
 
 (define-syntax (datalog-clause stx)
   (syntax-parse 
    stx
    #:literals (:-)
-   [(_ (:- head body ...))
-    (quasisyntax/loc stx
-      (clause #'#,stx (datalog-literal head) 
+   [(_ (~and tstx (:- head body ...)))
+    (quasisyntax/loc #'tstx
+      (clause #'#,#'tstx (datalog-literal head) 
               (list (datalog-literal body) ...)))]
    [(_ e)
-    (quasisyntax/loc stx
-      (clause #'#,stx (datalog-literal e) empty))]))
+    (quasisyntax/loc #'e
+      (clause #'#,#'e (datalog-literal e) empty))]))
 
 (define-syntax (datalog-literal stx)
   (syntax-parse 
    stx
+   #:literals (:-)
    [(_ sym:id)
-    (quasisyntax/loc stx
-      (literal #'#,stx 'sym empty))]
-   [(_ (sym:id e ...))
-    (quasisyntax/loc stx
-      (literal #'#,stx 'sym 
+    (quasisyntax/loc #'sym
+      (literal #'#,#'sym 'sym empty))]
+   [(_ (~and tstx (sym:id arg ... :- ans ...)))
+    (quasisyntax/loc #'tstx
+      (external #'#,#'tstx 'sym sym
+                (list (datalog-term arg) ...)
+                (list (datalog-term ans) ...)))]
+   [(_ (~and tstx (sym:id e ...)))
+    (quasisyntax/loc #'tstx
+      (literal #'#,#'tstx 'sym 
                (list (datalog-term e)
                      ...)))]))
 
 (define-syntax (datalog-term stx)
   (syntax-parse 
    stx
-   [(_ sym:str)
-    (quasisyntax/loc stx
-      (constant #'#,stx 'sym))]
    [(_ sym:id)
     (cond
       [(identifier-binding #'sym 0)
-       (quasisyntax/loc stx
-         (constant #'#,stx sym))]
+       (quasisyntax/loc #'sym
+         (constant #'#,#'sym sym))]
       [(char-upper-case? (string-ref (symbol->string (syntax->datum #'sym)) 0))
-       (quasisyntax/loc stx
-         (variable #'#,stx 'sym))]
+       (quasisyntax/loc #'sym
+         (variable #'#,#'sym 'sym))]
       [else
-       (quasisyntax/loc stx
-         (constant #'#,stx 'sym))])]))
+       (quasisyntax/loc #'sym
+         (constant #'#,#'sym 'sym))])]
+   [(_ sym:expr)
+    (quasisyntax/loc #'sym
+      (constant #'#,#'sym sym))]))
 
 (provide datalog datalog!
          :- ! ~ ?)
diff --git a/collects/tests/datalog/eval.rkt b/collects/tests/datalog/eval.rkt
index 8864bd6639..3611fd5613 100644
--- a/collects/tests/datalog/eval.rkt
+++ b/collects/tests/datalog/eval.rkt
@@ -22,22 +22,17 @@
                            port->lines))
                  (filter (lambda (l)
                            (not (string=? l "")))
-                         (file->lines test-txt))
-                 ))
+                         (file->lines test-txt))))
+  
+  (define (test-files d)
+    (for ([f (in-list (directory-list d))]
+          #:when (regexp-match #rx"rkt$" (path->bytes f)))
+      (test-example (path->string (path-replace-suffix f #"")))))
   
   (test-suite
    (path->string examples-dir)
    
-   (test-example "ancestor")
-   (test-example "bidipath")
-   (test-example "laps")
-   (test-example "long")
-   (test-example "path")
-   (test-example "pq")
-   (test-example "revpath")
-   (test-example "says")
-   (test-example "true")
-   (test-example "tutorial")))
+   (test-files examples-dir)))
 
 (define eval-tests
   (test-suite
diff --git a/collects/tests/datalog/paren-examples/add1.rkt b/collects/tests/datalog/paren-examples/add1.rkt
new file mode 100644
index 0000000000..f89b1b08bf
--- /dev/null
+++ b/collects/tests/datalog/paren-examples/add1.rkt
@@ -0,0 +1,10 @@
+#lang datalog/sexp
+(? (add1 2 :- X))
+
+(! (:- (add2 X Y)
+       (add1 X :- Z)
+       (add1 Z :- Y)))
+
+(? (add2 1 3))
+
+(? (add1 X :- 1))
\ No newline at end of file
diff --git a/collects/tests/datalog/paren-examples/add1.txt b/collects/tests/datalog/paren-examples/add1.txt
new file mode 100644
index 0000000000..dc6a141334
--- /dev/null
+++ b/collects/tests/datalog/paren-examples/add1.txt
@@ -0,0 +1,3 @@
+add1(2) = (3).
+
+add2(1, 3).
diff --git a/collects/tests/datalog/paren-examples/req.rkt b/collects/tests/datalog/paren-examples/req.rkt
new file mode 100644
index 0000000000..c7cfb8d651
--- /dev/null
+++ b/collects/tests/datalog/paren-examples/req.rkt
@@ -0,0 +1,4 @@
+#lang datalog/sexp
+(require racket/math)
+
+(? (sqr 4 :- X))
\ No newline at end of file
diff --git a/collects/tests/datalog/paren-examples/req.txt b/collects/tests/datalog/paren-examples/req.txt
new file mode 100644
index 0000000000..8cc557431d
--- /dev/null
+++ b/collects/tests/datalog/paren-examples/req.txt
@@ -0,0 +1 @@
+sqr(4) = (16).
diff --git a/collects/tests/datalog/private/subst.rkt b/collects/tests/datalog/private/subst.rkt
index 2871f40eb7..2dc0a48236 100644
--- a/collects/tests/datalog/private/subst.rkt
+++ b/collects/tests/datalog/private/subst.rkt
@@ -85,14 +85,14 @@
                                          'v1))))
    
    (test-suite
-    "rename-literal"
-    (test-equal? "l" (rename-literal (make-literal #f 'lit (list (make-constant #f 'v1))))
+    "rename-question"
+    (test-equal? "l" (rename-question (make-literal #f 'lit (list (make-constant #f 'v1))))
                  (make-literal #f 'lit (list (make-constant #f 'v1))))
     (test-not-false "l"
                     (gensym-var?
                      (first
                       (literal-terms
-                       (rename-literal (make-literal #f 'lit (list (make-variable #f 'v1)))))))))
+                       (rename-question (make-literal #f 'lit (list (make-variable #f 'v1)))))))))
    
    (test-suite
     "rename-clause"
diff --git a/collects/tests/datalog/private/unify.rkt b/collects/tests/datalog/private/unify.rkt
index 2ea94e61a5..688c3812c2 100644
--- a/collects/tests/datalog/private/unify.rkt
+++ b/collects/tests/datalog/private/unify.rkt
@@ -3,7 +3,7 @@
          datalog/ast
          datalog/private/env
          datalog/private/unify)
-(require/expose datalog/private/unify (chase unify-terms))
+(require/expose datalog/private/unify (chase))
 
 (provide unify-tests)
 
diff --git a/collects/tests/datalog/racket.rkt b/collects/tests/datalog/racket.rkt
index 39a67167e7..439aa743b0 100644
--- a/collects/tests/datalog/racket.rkt
+++ b/collects/tests/datalog/racket.rkt
@@ -54,4 +54,9 @@
  (list '(parent joseph2 joseph1)
        '(parent joseph2 lucy))
  
+ (datalog parent
+          (? (add1 1 :- X)))
+ =>
+ (list '(add1 1 :- 2))
+ 
  )
\ No newline at end of file