17.2. Anonymous Explicit Bridges
A link to another domain is effected by actions that generate signals or synchronously invoke defined operations on an external entity. The domain to which the external entity refers remains anonymous.
17.2.1. External Entities
Each domain's models include a number of external entities. External entities are not domains themselves; rather, they act as anonymous proxies to other domains. This notion of anonymity is important: There are times when a domain requires something of some other domain—for example, the bookstore needs signals to initiate activities—but the models of the bookstore domain need to be independent of the methods by which those signals originate.
External entities are represented on the collaboration ...