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Created March 8, 2012 18:39
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Datomic extent query
;; 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]]]
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