Abstract We present the semantics and proof system for an objectoriented language with active objects, asynchronous method calls, and futures. The language, based on Creol, distinguishes itself in that unlike active object models, it permits more than one thread of control within an object, though, unlike Java, only one thread can be active within an object at a given time and rescheduling occurs only at specific release points. Consequently, reestablishing an object’s monitor invariant is possible at specific well-defined points in the code. The resulting proof system shows that this approach to concurrency is simpler for reasoning than, say, Java’s multithreaded concurrency model. From a methodological perspective, we identify constructs which admit a simple proof system and those which require, for example, interference freedom tests. 1

We present the propositional fragment CLF0 of the Concurrent Logical Framework (CLF). CLF extends the Linear Logical Framework to allow the natural representation of concurrent computations in an object language. The underlying type theory uses monadic types to segregate values from computations. This separation leads to a tractable notion of definitional equality that identifies computations di#ering only in the order of execution of independent steps. From a logical point of view our type theory can be seen as a novel combination of lax logic and dual intuitionistic linear logic. An encoding of a small Petri net exemplifies the representation methodology, which can be summarized as "concurrent computations as monadic expressions ".

Concurrent programs require high-level abstractions in order to manage complexity and enable compositional reasoning. In this paper, we introduce a novel concurrency abstraction, dubbed transactional events, which combines first-class synchronous message passing events with all-or-nothing transactions. This combination enables simple solutions to interesting problems in concurrent programming. For example, guarded synchronous receive can be implemented as an abstract transactional event, whereas in other languages it requires a non-abstract, non-modular protocol. As another example, three-way rendezvous can be implemented as an abstract transactional event, which is impossible using first-class events alone. Both solutions are easy to code and easy to reason about. The expressive power of transactional events arises from a sequencing combinator whose semantics enforces an all-or-nothing transactional property – either both of the constituent events synchronize in sequence or neither of them synchronizes. This sequencing combinator, along with a non-deterministic choice combinator, gives transactional events the compositional structure of a monad-with-plus. We provide a formal semantics for transactional events and give a detailed account of an implementation.

A session type is an abstraction of a set of sequences of heterogeneous values sent and received over a communication channel. Session types can be used for specifying stream-based Internet protocols.

As part of ongoing work on evaluating Milner’s bigraphical reactive systems, we investigate bigraphical models of context-aware systems, a facet of ubiquitous computing. We find that naively encoding such systems in bigraphs is somewhat awkward; and we propose a more sophisticated modeling technique, introducing Plato-graphical models, alleviating this awkwardness. We argue that such models are useful for simulation and point out that for reasoning about such bigraphical models, the bisimilarity inherent to bigraphical reactive systems is not enough in itself; an equivalence between the bigraphical reactive systems themselves is also needed.

We introduce a new lambda calculus with futures, λ(fut), to model the operational semantics of concurrent extensions of ML. λ(fut) can safely express a variety of high-level concurrency constructs, including channels, semaphores, or ports. Safe implementations of these constructs in (fut) cannot be corrupted in any well-typed context. We prove safety on basis of a linear type system.

This is a tutorial on using type-indexed embedding/projection pairs when writing interpreters in statically-typed functional languages. The method allows (higher-order) values in the interpreting language to be embedded in the interpreted language and values from the interpreted language may be projected back into the interpreting one. This is particularly useful when adding command-line interfaces or scripting languages to applications written in functional languages. We first

We present Alice, a functional programming language that has been designed with strong support for typed open programming. It incorporates concurrency with data flow synchronisation, higher-order modularity, dynamic modules, and type-safe pickling as a minimal and generic set of simple, orthogonal features providing that support. Based on these mechanisms Alice offers a flexible notion of component, and high-level facilities for distributed programming.

The increasing availability of commodity multicore processors is making parallel computing available to the masses. Traditional parallel languages are largely intended for large-scale scientific computing and tend not to be well-suited to programming the applications one typically finds on a desktop system. Thus we need new parallel-language designs that address a broader spectrum of applications. In this paper, we present Manticore, a language for building parallel applications on commodity multicore hardware including a diverse collection of parallel constructs for different granularities of work. We focus on the implicitly-threaded parallel constructs in our high-level functional language. We concentrate on those elements that distinguish our design from related ones, namely, a novel parallel binding form, a nondeterministic parallel case form, and exceptions in the presence of data parallelism. These features differentiate the present work from related work on functional data parallel language designs, which has focused largely on parallel problems with regular structure and the compiler transformations — most notably, flattening — that make such designs feasible. We describe our implementation strategies and present some detailed examples utilizing various mechanisms of our language.

Type systems for programming languages help reasoning about program behavior and early finding of bugs. Recent applications of type systems include analysis of various program behaviors such as side effects, resource usage, security properties, and concurrency. This paper is a tutorial of one of such applications: type systems for analyzing behavior of concurrent processes. We start with a simple type system and extend it step by step to obtain more expressive type systems to reason about deadlock-freedom, safe usage of locks, etc.