(set *semantic-net* (vector 1000)) 

(define query  
   [is Object Concept] -> (if (belongs? Object Concept) yes no))

(define belongs?  
   Object Concept 
   -> (element? Concept (fix (fn spread-activation) [Object])))

(define spread-activation  
   [ ] -> [ ] 
   [Vertex  |  Vertices]  
  -> (union (accessible-from Vertex) (spread-activation Vertices)))

(define accessible-from  
   Vertex -> [Vertex | (union (is_links Vertex) (type_links Vertex))])

(define is_links  
   Vertex -> (trap-error (get Vertex is_a (value *semantic-net*))  (/. E [])))

(define type_links 
  Vertex -> (trap-error (get Vertex type_of (value *semantic-net*))  (/. E [])))

(define assert
   [Object is_a Type] 
    -> (put Object is_a (adjoin Type (is_links Object)) (value *semantic-net*))
   [Type1 type_of Type2] 
   -> (put Type1 type_of (adjoin Type2 (type_links Type1)) (value *semantic-net*)))