References: Yonezawa, Shibayama, Takada, Honda, Modelling and Programming in an Object-Oriented Concurrent Language ABCL/1

FTP directory with some information: ABCL

Main Concepts

Scripts, patterns and constraints. An object has its own processing power and persistent state. Each object has a script that specifies its behavior. In ABCL/1, the behavior of an object is determined by the messages it accepts and the actions it performs when it receives each message. Message patterns and constraints are used to indicate the set of messages an object may accept.

Modes. Any object is on one of three modes: dormant, active, or waiting. An object is initially dormant, then becomes active when it receives a message that satisfies one of its patterns and constraints. When an object completes the sequence of actions in response to an accepted message, it becomes dormant again. An active object may wait for a message satsifying a specific pattern. In this case, it becomes active again once such a message is received.

Communication. Communication is point-to-point, with one sender and one receiver. An object may send a message to any other object as long as it knows the name of the object. Message transmission is asynchronous in the sense that an object may send a message to another, regardless of the state or mode of the other object.


[object object-name
    (state representation-of-local-memory)
      (=>  message-pattern where constraint   ...action...  )
      (=>  message-pattern where constraint   ...action...  ))]