The same entity can be referenced by other entities through attribute which is component

Datomic Pro
1

E.g. I’m transacting schema

(def movie-schema [
                   {
                       :db/ident :org/code
                       :db/valueType :db.type/string
                       :db/cardinality :db.cardinality/one
                       :db/unique :db.unique/value
                   }
                   {
                       :db/ident :org/users
                       :db/valueType :db.type/ref
                       :db/cardinality :db.cardinality/many
                       :db/isComponent true
                   }
                   {
                       :db/ident :user/name
                       :db/valueType :db.type/string
                       :db/cardinality :db.cardinality/one
                       :db/unique :db.unique/value
                   }

                           ])
(d/transact conn movie-schema)

Where :org/users is component

And data according to the schema:

(def first-movies 
[
    {
    	  :db/id "user1"
          :user/name "user1"
    }
    {
    	  :db/id "user2"
          :user/name "user2"
    }

    {
          :org/code "org1"
          :org/users ["user1" "user2"]
    }

    {
          :org/code "org2"
          :org/users ["user1" "user2"]
    }

])

Actually I would expect that datomic will fail such transaction because of trying to set the same users among different organizations otherwise an example provided on datomic blog for Order and its LineItem is invalid because the same LineItem can’t be shared across more then one order

2

@marshall Could you please provide your thought on this issue, I believe it should be fundamental things, thanks

3

As you mentioned, having an entity be a component of multiple “parents” is generally not something you want to do, and I would argue it is a misuse of isComponent.
However, Datomic does not enforce this semantic.