4.1.10 Connections

The definition of connections is not required for servers, the models that passively wait for incoming service requests, and provide those services to the clients.

In the clients, connections must be specified in addition to the ports. The clients must also locate the servers. A specific implementation of DCharts may provide a number of ways to locate those servers. The following mechanisms are most common:

• Locate servers by their names. The clients specify name patterns of the servers that they want to connect to. All the servers with names matching those name patterns are selected by the simulation/execution environments. They attempt to establish the required connections between the servers and the clients. The name patterns are strings of UNIX regular expressions.

• Locate servers by their types. The clients specify types of the servers. The type of a model is an unordered list of the types of all its ports. For example, the type of a model with 2 in-ports, 1 out-port and 3 inout-ports is $\{in,in,out,inout,inout,inout\}$. This scheme selects all the servers that match a given type.

• Locate servers by their behavioral keywords. A server may define several keywords that define its behavior or the services that it provides. If so, the clients can use the keywords to match the servers.

• Any combination of the above schemes.

Figure 4.14: An example of the graphical representation of connections

The graphical representation of three connections is given in Figure 4.14. The scheme to locate the server is a property of the connections and is not shown graphically. Connections are the links between the ports and the server. A connection must also specify the port of the server to which the client is connected. This specification is not shown graphically, either.

In the figure, port p, because it is an inout-port (supporting input, output, or both), can be connected to ports of any type of the server; q can only be connected to out-ports or inout-ports of the server; r can only be connected to in-ports or inout-ports of the server.

Figure 4.15: Alternate graphical representation of connections in AToM$^3$

The graphical representation of connections is a little different in AToM$^3$ (Figure 4.15).