Groups of Ports

Ports can be assembled into groups. The concept of group extends port-to-port addressing between threads by adding a synchronous multicast facility. Alternatively, functional access to a service can be selected from among a group of (equivalent) services using port groups.

Creating a group of ports only allocates a name for the group. Ports can then be inserted into the group and it is built dynamically. A port can be removed from a group. Groups cannot contain other groups.

Like an actor, a group is named by a capability. This capability contains a unique identifier (UI), specific to the group. This UI can be used for sending messages to the ports in the group. The full group capability is needed to modify the group configuration (inserting ports in and removing ports from the group).

Like ports, messages are addressed to port groups by their UI. In the case of a group UI, the address is accompanied by an address mode. The possible address modes are:

• Broadcast to all ports in the group (broadcast mode).

• Addressing one of the ports of the group, selected arbitrarily (functional mode).

• Addressing one of the ports of the group, located on the same site as a given object designated by its UI (associative functional mode).

• Addressing one of the ports of the group, assuming that the selected port UI is on a different site from that of a given UI (exclusive functional mode).