Clojurians Log v2

Is there a way to build hierarchies in rules engines/precept? i'm trying to understand the relationship between rules and datomic's query language in general. Specifically, i see how in precept you can build a subscription to a single entity:

(defsub :visible-todos
  [[?e :todo/visible true]]
  [(<- ?todo (entity ?e))]
  =>
  {:visible-todo ?todo}

but is there a way to mimic the datomic pull syntax? that is, build a isComponent type relationship?