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The Saga of the Axiomatization of Parallel Composition ⋆
"... Abstract. This paper surveys some classic and recent results on the finite axiomatizability of bisimilarity over CCSlike languages. It focuses, in particular, on nonfinite axiomatizability results stemming from the semantic interplay between parallel composition and nondeterministic choice. The pa ..."
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Abstract. This paper surveys some classic and recent results on the finite axiomatizability of bisimilarity over CCSlike languages. It focuses, in particular, on nonfinite axiomatizability results stemming from the semantic interplay between parallel composition and nondeterministic choice. The paper also highlights the role that auxiliary operators, such as Bergstra and Klop’s left and communication merge and Hennessy’s merge operator, play in the search for a finite, equational axiomatization of parallel composition both for classic process algebras and for their realtime extensions. 1 The Problem and its History Process algebras are prototype description languages for reactive systems that arose from the pioneering work of figures like Bergstra, Hoare, Klop and Milner. Wellknown examples of such languages are ACP [18], CCS [44], CSP [40] and Meije [13]. These algebraic description languages for processes differ in the basic collection of operators that they offer for building new process descriptions from existing ones. However, since they are designed to allow for the description and analysis of systems of interacting processes, all these languages contain some form of parallel composition (also known as merge) operator allowing one to put two process terms in parallel with one another. These operators usually interleave the behaviours of their arguments, and support some form of synchronization between them. For example, Milner’s CCS offers the binary operator , whose intended semantics is described by the following classic rules in the style of Plotkin [49]. x µ → x ′ x   y µ → x ′   y y µ → y ′ x   y µ → x   y ′ x α → x ′ , y ¯α → y ′ x   y τ → x ′   y ′ (In the above rules, the symbol µ stands for an action that a process may perform, α and ¯α are two observable actions that may synchronize, and τ is a symbol denoting the result of their synchronization.)
Hume box calculus: robust system development through software transformation
 HIGHERORDER SYMB COMPUT
, 2011
"... Hume is a contemporary programming language oriented to systems with strong resource bounds, based on autonomous concurrent “boxes” interacting across “wires”. Hume’s design reflects the explicit separation of coordination and computation aspects of multiprocess systems, which greatly eases establi ..."
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Hume is a contemporary programming language oriented to systems with strong resource bounds, based on autonomous concurrent “boxes” interacting across “wires”. Hume’s design reflects the explicit separation of coordination and computation aspects of multiprocess systems, which greatly eases establishing resource bounds for programs. However, coordination and computation are necessarily tightly coupled in reasoning about Hume programs. Furthermore, in Hume, local changes to coordination or computation, while preserving input/output correctness, can have profound and unforeseen effects on other aspects of programs such as timing of events and scheduling of processes. Thus, traditional program calculi prove inappropriate as they tend to focus exclusively either on the coordination of interacting processes or on computation within individual processes. The Hume box calculus offers a novel approach to manipulating multiprocess systems by accounting seamlessly for both coordination and computation in individual rules. Furthermore, the “Hierarchical Hume” extension enables strong locality of the effects of program manipulation, as well as providing a principled encapsulation mechanism. In this paper, we present an overview of the Hume box calculus and its applications in program development. First of all, a base set of rules for introducing, changing, composing, separating and eliminating Hume boxes and wires, possibly within hierarchies, is presented. Next additional strategies are derived and a constructive approach to program development is illustrated through two examples of system elaboration from truth tables. Finally, at a considerably higher level, the use of the Hume box calculus to verify a generic transformation from a single box to an equivalent multibox program, offering a balanced parallel implementation, is discussed.
On Linear Logic Planning and Concurrency
"... We present an approach to linear logic planning where an explicit correspondence between partial order plans and multiplicative exponential linear logic proofs is established. This is performed by extracting partial order plans from sound and complete encodings of planning problems in multiplicativ ..."
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We present an approach to linear logic planning where an explicit correspondence between partial order plans and multiplicative exponential linear logic proofs is established. This is performed by extracting partial order plans from sound and complete encodings of planning problems in multiplicative exponential linear logic in a way that exhibits a noninterleaving behavioral concurrency semantics. Relying on this fact, we argue that this work is a crucial step for establishing a common language for concurrency and planning that will allow to carry techniques and methods between these two fields.
C.: From individuals to populations: A mean field semantics for process algebra
 Theor. Comput. Sci
, 2011
"... A new semantics in terms of Mean Field Equations is presented for WSCCS (Weighted Synchronous Calculus of Communicating Systems). The semantics captures the average behaviour of the system over time, but without computing the entire state space, therefore avoiding the state space explosion problem. ..."
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A new semantics in terms of Mean Field Equations is presented for WSCCS (Weighted Synchronous Calculus of Communicating Systems). The semantics captures the average behaviour of the system over time, but without computing the entire state space, therefore avoiding the state space explosion problem. This allows easy investigation of models with large numbers of components. The new semantics is shown to be equivalent to the standard Discrete Time Markov Chain semantics of WSCCS as the number of processes tends to infinity. The method of deriving the semantics is illustrated with examples drawn from biology and from computing.
1 Getting it Right the First time: Robot Mission Guarantees in the Presence of Uncertainty*
"... Abstract—Certain robot missions need to perform predictably in a physical environment that may only be poorly characterized in advance. We have previously developed an approach to establishing performance guarantees for behaviorbased controllers in a processalgebra framework. We extend that work he ..."
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Abstract—Certain robot missions need to perform predictably in a physical environment that may only be poorly characterized in advance. We have previously developed an approach to establishing performance guarantees for behaviorbased controllers in a processalgebra framework. We extend that work here to include random variables, and we show how our prior results can be used to generate a Dynamic Bayesian Network for the coupled system of program and environment model. Verification is reduced to a filtering problem for this network. Finally, we present validation results that demonstrate the effectiveness of the verification of a multiple waypoint robot mission using this approach. I.
Modeling Time in Computing: A . . .
, 2010
"... The increasing relevance of areas such as realtime and embedded systems, pervasive computing, hybrid systems control, and biological and social systems modeling is bringing a growing attention to the temporal aspects of computing, not only in the computer science domain, but also in more traditiona ..."
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The increasing relevance of areas such as realtime and embedded systems, pervasive computing, hybrid systems control, and biological and social systems modeling is bringing a growing attention to the temporal aspects of computing, not only in the computer science domain, but also in more traditional fields of engineering. This article surveys various approaches to the formal modeling and analysis of the temporal features of computerbased systems, with a level of detail that is also suitable for nonspecialists. In doing so, it provides a unifying framework, rather than just a comprehensive list of formalisms. The article first lays out some key dimensions along which the various formalisms can be evaluated and compared. Then, a significant sample of formalisms for time modeling in computing are presented and discussed according to these dimensions. The adopted perspective is, to some extent, historical, going from “traditional” models and formalisms to more modern ones.
Multidisciplinary Modeling Current status and expectations in the Dutch TWINS consortium
"... Abstract: The TWINS project addresses industrial hardwaresoftware codesign product development. In search for a multidisciplinary modeling solution, knowledge is required about the current practice of multidisciplinary development in industry. By analyzing user requirements, use cases, and applied ..."
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Abstract: The TWINS project addresses industrial hardwaresoftware codesign product development. In search for a multidisciplinary modeling solution, knowledge is required about the current practice of multidisciplinary development in industry. By analyzing user requirements, use cases, and applied tools and techniques of six industrial partners, this paper presents the current status of multidisciplinary development in the Dutch consortium. The analysis is used to improve a successful collaboration between the industrial partners, and it also identifies the challenging topics that need to be explored within a multidisciplinary environment.
A Formal Approach to Specifying and Verifying Spacecraft Behavior
, 2007
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"... This dissertation has not been submitted as an exercise for a degree at any other University. Except where otherwise stated, the work described herein has been carried out by the author alone. This dissertation may be borrowed or copied upon request with the permission of the Librarian, University o ..."
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This dissertation has not been submitted as an exercise for a degree at any other University. Except where otherwise stated, the work described herein has been carried out by the author alone. This dissertation may be borrowed or copied upon request with the permission of the Librarian, University of