10.6.2 Binding

Communication between components is achieved through component ports. The lines of communication are established by binding ports:

binding   ::= end-point "<=>" end-point ";"
end-point ::= port-name
              | wildcard
              | (instance-name "." port-name)
              | (instance-name "." wildcard)
wildcard  ::= "*"

Note that bindings are symmetrical, i.e., left and right end-points can be exchanged. Communication is restricted to ports of the same (interface) type. Moreover the communication ’direction’ has to be compatible. There are two cases:

• Two sub components communicating: always a provides port binds to a requires port, like in top.rr <=> middle.pp in the top_middle_bottom system example above.
• In the case of port forwarding, where a sub-component port is exposed as a system port, the directions of the ports must be the same, like in p <=> top.pp and bottom.rr <=> r in the top_middle_bottom system example above.

• Using Injection