@Override
        public boolean equals( final Object o )
        {
            if ( this == o ) { return true; }
            if ( o == null || getClass() != o.getClass() ) { return false; }
            final UniqueIdentifier that = (UniqueIdentifier) o;
            return serviceId.equals( that.serviceId );
        }
A unique identifier for an item, in context of all nodes of all services in the system.

The property that uniquely identifies a service within the system is its serviceId.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/PubSubService.java