Einar Broch Johnsen

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This paper presents ABS, an abstract behavioral specification language for designing executable models of distributed object-oriented systems. The language combines advanced concurrency and synchronization mechanisms for concurrent object groups with a functional language for modeling data. ABS uses asynchronous method calls, interfaces for encapsulation,(More)
Distributed systems are often modeled by objects that run concurrently, each with its own processor, and communicate by synchronous remote method calls. This may be satisfactory for tightly coupled systems, but in the distributed setting synchronous external calls lead to much waiting; at best resulting in inefficient use of processor capacity, at worst(More)
Object-oriented distributed computing is becoming increasingly important for critical infrastructure in society. In standard object-oriented models, objects synchronize on method calls. These models may be criticized in the distributed setting for their tight coupling of communication and synchronization; network delays and instabilities may locally result(More)
Active objects offer a structured approach to concurrency, encapsulating both unshared state and a thread of control. For efficient data transfer, data should be passed by reference whenever possible, but this introduces aliasing and undermines the validity of the active objects. This paper proposes a minimal variant of ownership types that preserves the(More)
This volume collects a set of papers accompanying the lectures of the 15th International School on Formal Methods for the Design of Computer, Communication and Software Systems (SFM). This series of schools addresses the use of formal methods in computer science as a prominent approach to the rigorous design of the above-mentioned systems. The main aim of(More)
The Abstract Behavioral Specification (ABS) language facilitates to precisely model the behavior of highly configurable, distributed systems. Its basis is Core ABS which is a strongly typed, abstract, objectbased, concurrent, fully executable modeling language. Spatial variability of ABS models is represented by feature models, delta modules containing(More)
Delta-oriented programming is a modular, yet flexible technique to implement software product lines. To efficiently verify the specifications of all possible product variants of a product line, it is usually infeasible to generate all product variants and to verify them individually. To counter this problem, we propose a transformational proof system in(More)
An application’s quality of service (QoS) depends on resource availability; e.g., response time is worse on a slow machine. On the cloud, a virtualized application leases resources which are made available on demand. When its work load increases, the application must decide whether to reduce QoS or increase cost. Virtualized applications need to manage(More)