Summary Checklist

• Component-and-connector (C&C) views define models consisting of elements that have some runtime presence, such as processes, objects, clients, servers, and data stores. Additionally, component-and-connector models include as elements the pathways of interaction, such as communication links and protocols, information flows, and access to shared storage.
• Components have interfaces, which are called ports.
• Connectors have interfaces, which are called roles.
• Connectors need not be binary, meaning that they may have more than two roles. Even if the connector is ultimately implemented using binary connectors, such as a procedure call, it can be useful to adopt n-ary connector representations at an architectural level.
• If a component's primary purpose is to mediate interaction between a set of components, consider representing it as a connector instead.
• Connectors can and often should represent complex forms of interaction. Even a semantically simple procedure call can be complex when carried out in a distributed setting, involving runtime protocols for timeouts, error handling, and locating the service provider.
• Connectors embody a protocol of interaction. When two or more components interact, they must obey conventions about order of interactions, locus of control, and handling of error conditions and timeouts. When providing a detailed description of a connector, the documentation should attempt to capture this detail.
• Be clear about which style you are using, by referring to an appropriate style guide.
• Make clear which port is used when attaching a component to a connector.
• If it is not clear that it is valid to attach a given port with a given role, provide a justification in the rationale section for the view.
• Make clear which ports are used to connect the system to its external environment.
• Data flow and control flow diagrams are projections of C&C models. When creating such diagrams, be explicit about the semantic criteria being used to determine where the arrows go. Data flow and control flow projections are at best ap-proximations to the connectors, which define the components' interactions.