Datomic extent query

gistfile1.clj

;; Datomic example code
;;
;; The extent of entity ?x is all datoms that are about ?x.
;; Drop this into your rules.
;;
;; Demonstrates
;;
;; 1. recursive query (extent calls itself)
;; 2. disjunction (different extent bodies are ORed)
;; 3. component attributes (e.g. your arm is a component, your brother isn't)
;; 4. navigating inbound and outbound references

'[[(extent ?x ?e ?a ?v)   ;; match datoms where x is entity...
   [?e ?a ?v]
   [?x ?a ?v]
   [(= ?e ?x)]]
  [(extent ?x ?e ?a ?v)   ;; ...or match datoms where x is value
   [?e ?a ?v]
   [?e ?a ?x]
   [(= ?v ?x)]]
  [(extent ?x ?e ?a ?v)   ;; recurse where y is a component of x
   (components ?x ?y)
   (extent ?y ?e ?a ?v)]
  [(components ?p ?c)     ;; only follow component attributes
   [?a :db/isComponent]
   [?p ?a ?c]]]