A Dynamic Binding Strategy for Multiple Inheritance and Asynchronously Communicating Objects

Abstract

This paper considers an integration of asynchronous communication, virtual binding, and multiple inheritance. Object orientation is the leading paradigm for concurrent and distributed systems, but the tightly synchronized RPC communication model seems unsatisfactory in the distributed setting. Asynchronous messages are better suited, but lack the structure and discipline of traditional object-oriented methods. The integration of messages in the object-oriented paradigm is unsettled, especially with respect to inheritance and redefinition. Asynchronous method calls have been proposed in the Creol language, reducing the cost of waiting for replies in the distributed environment while avoiding lowlevel synchronization constructs such as explicit signaling. A lack of reply to a method call need not lead to deadlock in the calling object. Creol has an operational semantics defined in rewriting logic. This paper considers a formal operational model of multiple inheritance, virtual binding, and asynchronous communication between concurrent objects, extending the semantics of Creol.

Incremental reasoning with lazy behavioral subtyping for multiple inheritance

“…We say that a call to a method m is bound with respect to a search class D; i.e., bind(D, m) denotes the search for a definition of m which starts in D. In this case, the call must bind to a definition of m in a class above D, such that no other definition of m is found by the search below this class. Following [10,13,22] where D.inh D reduces to D when D.inh is empty. Observe that this strategy is not healthy, since an internal call would be bound independently of where the call-site occurs in the class hierarchy, i.e., the class in which the call textually occurs.…”

“…This may be due to the complexity of resolving method binding, as discussed in Section 2, which may easily cause ambiguities. However, multiple inheritance is supported in, e.g., C++ [38], CLOS [13], Eiffel [29], Ocaml [26], POOL [2], Self [10], and Creol [22]. Horizontal name conflicts in C++, POOL, and Eiffel are removed by explicit resolution, after which the inheritance graph may be linearized.…”

Type-Safe Runtime Class Upgrades in Creol

“…3 Creol: A Language for Distributed Concurrent Objects Creol is a high-level object-oriented language targeting open distributed systems by combining interface types and concurrent objects with asynchronous method calls, and by combining active and reactive object behavior [13,15]. In this paper blocking and nonblocking (suspending) method calls are considered, although the results of the paper apply to the full language.…”

“…The class identifier for version n of class C is denoted C#n. The rules for the static language constructs may be found in [13]. Focus here is on method binding and dynamic class constructs, given in Figure 5.…”

“…This paper considers a type-safe mechanism for distributed runtime updates in Creol [13], a formally defined object-oriented language which specifically targets open distributed systems. We consider updates in the form of runtime upgrades of existing classes combined with runtime additions of new interfaces and new classes.…”