A single fortress by itself is not very interesting. It is the relationship between fortresses that defines the enterprise architecture. A fortress–ally diagram (FAD) shows all of the enterprise fortresses and the ally relationships between them. Figure 2.2 shows an example of a FAD for a bill payment system.
The important features of a FAD are as follows:
Each fortress should be identified with a name and a type in the format name::type so that the appropriate fortress overview can be consulted for more detail.
Each drawbridge should be identified (with either labeled arrows or boxes) so that ...