Improving Polymorphism and Concurrency in Common Object Models

computer. An abstract computer consists of communication channels that can be used to communicate with every other abstract computer in the system. It also contains an application manager that manages the applications running in the system. A computer in a network can represent a node or multiple nodes can exist on one computer. A Distributed Act++ environment provides dedicated actors for communication between the nodes in the system. Each node in the system is connected to every other node via two dedicated communication actors called MsgReceiver and MsgSender. The MsgSender actor sends messages and the MsgReceiver actor receives messages meant for that node. If there are N nodes in the system, each node has (N-1) MsgSender actors and (N-1) MsgReceiver actors in the system. So the number of dedicated actors used for communication between nodes is (N-1)*(N-1) MsgSender actors and (N-1)*(N-1) MsgReceiver actors. A distributed actor system with two nodes on two different machines is shown in Figure 3.6. Each machine can support one or more nodes in the distributed actor system. One of the nodes is treated as the main node that acts as a centralized manager. Before joining the system, every other node has to establish communications with the main node. The main node helps the new node to establish communication channels with every other node in the system. The communication channels are represented in the figure as MsgSender and MsgReceiver. These channels are managed by dedicated actors whose sole purpose is to send and receive information respectively, from the nodes they represent. There is a Boot actor object that creates the AppMgr actor at any node. The AppMgr actor keeps track of all applications currently executing in the system. The initialization of the system and the communication between various actors is described below. The Distributed Act++ environment requires an initial setup that makes the communicating nodes (on possibly distributed machines) aware of the existence of CHAPTER 3. INTEROPERABLE COMMON OBJECT MODEL (ICOM) 56