Stateful Behavioral Types for Active Objects

Abstract

It is notoriously hard to correctly implement a multiparty protocol which involves asynchronous/concurrent interactions and constraints on states of multiple participants. To assist developers in implementing such protocols, we propose a novel specification language to specify interactions within multiple object-oriented actors and the sideeffects on heap memory of those actors. A behavioral-type-based analysis is presented for type checking. Our specification language formalizes a protocol as a global type, which describes the procedure of asynchronous method calls, the usage of futures, and the heap side-effects with a firstorder logic. To characterize runs of instances of types, we give a modeltheoretic semantics for types and translate them into logical constraints over traces. We prove protocol adherence: If a program is well-typed w.r.t. a protocol, then every trace of the program adheres to the protocol, i.e., every trace is a model for the formula of the protocol's type.

Crowbar: Behavioral Symbolic Execution for Deductive Verification of Active Objects

“…Example 2. We give a simple example using our session type system [21]: the following expresses that the statement s first calls method m on role f and then n on role g. Finally, the last action is a return in a state where ϕ holds. No other communication, synchronization or suspension happens.…”

“…The mapping of roles to fields is specified with [Spec: Role("name",this.field)]. For details we refer to [19,20,21].…”

Behavioral Program Logic and LAGC Semantics without Continuations (Technical Report)

“…Behavioral types, especially session types [25], are restricted in their expressive power to easily compose their local results to global guarantees, and are natural specifications for protocols. However, they lack precision when handling state [6] or require additional static analyses [29]. For Active Objects [13] (object-oriented actors with futures), a translation from session types to a trace logic has been given [29].…”

“…However, they lack precision when handling state [6] or require additional static analyses [29]. For Active Objects [13] (object-oriented actors with futures), a translation from session types to a trace logic has been given [29].…”

“…Our main contributions are (1) BPL, a trace program logic that integrates deductive reasoning with static analyses (2) method types, a behavioral type in BPL that generalizes method contracts, object invariants and local types for Active Objects. Decomposition and projection for Session Types for Active Objects are given in [29,30]. We introduce our programming language in Sec.…”