Composition is an important feature of a specification language, as it enables the design of a complex system in terms of a product of its parts. Decomposition is equally important in order to reason about structural properties of a system. Usually, however, a system can be decomposed in more than one way, each optimizing for a different set of criteria. We extend an algebraic component-based model for cyber-physical systems to reason about decomposition. In this model, components compose using a family of algebraic products, and decompose, under some conditions, given a corresponding family of division operators. We use division to specify invariant of a system of components, and to model desirable updates. We apply our framework to design a cyber-physical system consisting of robots moving on a shared field, and identify desirable updates using our division operator.

We propose a component-based semantic model for Cyber-Physical Systems (CPSs) wherein the notion of a component abstracts the internal details of both cyber and physical processes, to expose a uniform semantic model of their externally observable behaviors expressed as sets of sequences of observations. We introduce algebraic operations on such sequences to model different kinds of component composition. These composition operators yield the externally observable behavior of their resulting composite components through specifications of interactions of the behaviors of their constituent components, as they, e.g., synchronize with or mutually exclude each other's alternative behaviors. Our framework is expressive enough to allow articulation of properties that coordinate desired interactions among composed components within the framework, also as component behavior. We demonstrate the usefulness of our formalism through examples of coordination properties in a CPS consisting of two robots interacting through shared physical resources.

Abstract Correctness of the behavior of an adaptive system during dynamic adaptation is an important challenge to realize correct adaptive systems. Dynamic adaptation refers to changes to both the functionality of the computational entities that comprise a composite system, as well as the structure of their interconnections, in response to variations in the environment, e.g., the load of requests on a server system. In this research, we view the problem of correct structural adaptation as a supervisory control problem and synthesize a reconfiguration controller that guides the behavior of a system during adaptation. The reconfiguration controller observes the system behavior during an adaptation and controls the system behavior by allowing/disallowing actions in a way to ensure that a given property is satisfied and a deadlock is avoided. The system during adaptation is modeled using a graph transition system and properties to be enforced are specified using a graph automaton. We adapt a classical theory of supervisory control for synthesizing a controller for controlling the behavior of a system modeled using graph transition systems. This theory is used to synthesize a controller that can impose both behavioral and structural constraints on the system during an adaptation. We apply a tool that we have implemented to support our approach on a case study involving https servers.

Coordination languages, as Reo, have emerged for the specification and implementation of interaction protocols among concurrent entities. In this paper, we propose a framework for generating partially-distributed, partially-centralized implementations of Reo connectors to improve 1) build-time compilation and 2) run-time throughput and parallelism. Our framework relies on the definition of a new formal product operator on constraint automata (Reo's formal semantics), which enables the formally correct distribution of disjoint parts of a coordination scheme over different machines according to several possible motivations (e.g., performance, privacy, QoS constraints, resource availability, network topology). First, we describe the design and a proof-of-concept implementation of our framework. Then, in a case study, we show and explain how a generated connector implementation can be executed in the Cloud and supports Big Data coordination.

Ensuring transactional behavior of business processes and web service compositions is an essential issue in the area of service-oriented computing. Transactions in this context may require long periods of time to complete and must be managed using nonblocking techniques. Data integrity in long-running transactions (LRTs) is preserved using compensations, that is, activities explicitly programmed to eliminate the effects of a process terminated by a user or that failed to complete due to another reason. In this paper, we present a framework for behavioral modeling of business processes, focusing on their transactional properties. Our solution is based on the channel-based coordination language Reo, which is an expressive, compositional, and semantically precise design language admitting formal reasoning. The operational semantics of Reo is given by constraint automata (CA). We illustrate how Reo can be used for modeling termination and compensation handling in a number of commonly used workflow patterns, including sequential and parallel compositions, nested transactions, discriminator choice and concurrent flows with link dependences. Furthermore, we show how essential properties of LRTs can be expressed in LTL and CTL-like logics and verified using model checking technology. Our framework is supported by a number of Eclipse plug-ins that provides facilities for modeling, animation, and verification of LRTs to generate executable code for them.

In this paper, we present Reo2MC, a tool chain for the performance evaluation of coordination models. Given a coordination model represented by a stochastic Reo connector, Reo2MC is able to automatically generate the Quantitative Intentional Automaton (QIA) as its operational semantics, and the corresponding Continuous-Time Markov Chain (CTMC), which allows us to apply existing CTMC tools, e.g., PRISM, for performance analysis of Reo connectors. In support of understanding connector behavior and performance properties, the tool also provides the graphical representation of the QIA and Markov Chains.

The complex interactions appearing in service-oriented computing make coordination a key concern in service-oriented systems. In this paper, we present a fault-based method to generate test cases for component connectors from specifications. For connectors, faults are caused by possible errors during the development process, such as wrongly used channels, missing or redundant subcircuits, or circuits with wrongly constructed topology. We give test cases and connectors a unifying formal semantics by using the notion of design, and generate test cases by solving constraints obtained from the specification and faulty connectors. A prototype symbolic test case generator serves to demonstrate the automatizing of the approach.

Assuring Quality of Service (QoS) properties is critical in Service-Oriented Application (SOA) development. In this paper, we present an approach for specifying the QoS properties of services along multiple dimensions and selecting services for their composition in a way that optimizes the QoS of the result. We apply the integration of concerns paradigm to allow combined specification of QoS and functional properties by using Quantitative Constraint Automata, which integrate QoS aspects into service-oriented application development processes, mainly for service selection and composition.

Reo is an exogenous coordination language for compositional construction of the coordinating subsystems of component-based softwares. Constraint automaton has been proposed as the operational semantics of Reo networks. The main goal of this work is to prepare a model checking based verification environment for component-based systems, whose component connectors are modeled by Reo networks and constraint automata. We use the methods of compositional reduction and abstraction in model checking of component-based systems and their component connectors modeled by Reo.

No abstract available.

We investigate the use of a new concept in component communication during the coordination of Web Services, expressed by the channel based coordinating communication system called Reo. The role of Reo is to construct and manage connectors, the latter being patterns of connected channel communicators. The communication and coordination of components lying over a distributed address space has been dealt so far with stream or datagram connections created and controlled by the participating calculation and coordination components. Web services can take advantage of the Reo channel system that separates communication from computation concerns using components that have independent sink and source ports that can be attached to Web Services components, thus overcoming the problem of compatibility in distributed systems. The flow of information is entirely regulated by the channel interconnections.

In this paper, we discuss one of our experiments using the coordination language MANIFOLD to restructure an existing sequential numerical application into a concurrent application. The application was written in ANSI C and deals with a sparse-grid method for a transport problem. Our approach is simple and is in fact a cut-and-paste method. First, we try to identify and isolate components in the legacy source code (the cut). Second, we glue them together by writing coordinator modules (glue modules) with the help of a coordination language (the paste). We also give some performance results.

In this paper, we present Reo, which forms a paradigm for composition of software components based on the notion of mobile channels. Reo is a channel-based exogenous coordination model in which complex coordinators, called connectors , are compositionally built out of simpler ones. The simplest connectors in Reo are a set of channels with well-defined behaviour supplied by users. Reo can be used as a language for coordination of concurrent processes, or as a ‘glue language’ for compositional construction of connectors that orchestrate component instances in a component-based system. The emphasis in Reo is just on connectors and their composition, and not on the entities that connect to, communicate and cooperate through these connectors. Each connector in Reo imposes a specific coordination pattern on the entities (for example, components) that perform I/O operations through that connector, without the knowledge of those entities. Channel composition in Reo is a very powerful mechanism for construction of connectors. We demonstrate the expressive power of connector composition in Reo through a number of examples. We show that exogenous coordination patterns that can be expressed as (meta-level) regular expressions over I/O operations can be composed in Reo out of a small set of only five primitive channel types.

A coherent description of architectures provides insight, enables communication among different stakeholders and guides complicated (business and ICT) change processes. Unfortunately, so far no architecture description language exists that fully enables integrated enterprise modeling. In this paper we focus on the requirements and design of such a language. This language defines generic, organization-independent concepts that can be specialized or composed to obtain more specific concepts to be used within a particular organisation. It is not our intention to re-invent the wheel for each architectural domain: wherever possible we conform to existing languages or standards such as UML. We complement them with missing concepts, focusing on concepts to model the relationships among architectural domains. The concepts should also make it possible to define links between models in other languages. The relationship between architecture descriptions at the business layer and at the application layer (business-IT alignment) plays a central role.

MoCha is a middleware for distributed communication and collaboration using mobile channels as its medium. Channels allow directed, anonymous, and peer-to-peer communication among entities, while mobility ensures that the structure of their connections can change over time in arbitrary ways. MoCha provides communication mechanisms without requiring central servers or fixed network infrastructures, and it allows exogenous coordination between processes. In this paper we briefly introduce MoCha and discuss the implementation of an important channel type: the asynchronous FIFO mobile channel.

A workable approach for modernization of existing software into parallel/distributed applications is through coarse-grain restructuring. If, for instance, entire subroutines of legacy code can be plugged into a new structure, the investment required for the rediscovery of the details of what they do can be spared. The resulting renovated software can then take advantage of the improved performance offered by modern parallel/distributed computing environments, without rethinking or rewriting the bulk of their existing code. The authors discuss one of their experiments using the coordination language MANIFOLD to restructure an existing sequential numerical application written in Fortran 77, into a concurrent application.

In this paper we describe one experiment in which a new co-ordination language, called Manifold, is used to restructure an existing sequential Fortran 77 code from computational fluid dynamics (CFD), into a parallel application. Manifold is a co-ordination language developed at CWI (Centrum voor Wiskunde en Informatica) in the Netherlands. It is very well suited for applications involving dynamic process creation and dynamically changing (ir)regular communication patterns among sets of independent concurrent co-operating processes. With a simple but generic master/worker protocol, written in the Manifold language, we are able to reuse the existing code without rethinking or rewriting it. The performance evaluation of a standard 3D CFD problem shows that Manifold performs very well. Copyright © 2000 John Wiley & Sons, Ltd.

Isolating computation and communication concerns into separate pure computation and pure coordination modules enhances modularity, understandability and reusability of parallel and/or distributed software. MANIFOLD is a pure coordination language that encourages this separation. We use real, concrete, running ANIFOLD programs to demonstrate the concept of pure coordination modules and the advantage of their reuse in applications of different natures. Performance results for the examples presented in this paper show that the overhead of using MANIFOLD to achieve this enhanced modularity and reusability is in practice small, compared to the more conventional paradigms for the design and programming of parallel and distributed software. © 1998 John Wiley & Sons, Ltd.

The paper combines work done in the areas of asynchronous timed computations and coordination models in order to derive a framework able to express real-time coordination without adhering to special architectures or real-time programming languages. In particular, it is shown how the coordination language MANIFOLD can be used to support coordinators with bounded response time. The only assumption made about the coordinated components is that they adhere to some constraints as imposed by timed asynchronous computational models derived for concurrent constraint languages. The model can be used as a basis for building complex software and hardware systems with the distinct advantage of enhancing reusability of existing components. Indeed, it is already being used in a project aiming to develop distributed multimedia applications.

A workable approach for modernization of existing software into parallel/distributed applications is through coarse grain restructuring. If for instance, entire subroutines of legacy code can be plugged into the new structure, the investment required for the rediscovery of the details of what they do can be spared. The resulting renovated software can then take advantage of the improved performance offered by modern parallel/distributed computing environments, without rethinking or rewriting the bulk of their existing code. We discuss one of our experiments using the new coordination language MANIFOLD to restructure an existing sequential numerical application written in Fortran 77, into a parallel/distributed application.

Abstract The development of multimedia applications is a complex task. Much of this complexity stems from requirements associated with programming multiple media objects and the control of dependences and inter‐relationships between these media objects and the user(s). It is clearly necessary to have a basic framework on which to build multimedia applications in the face of such complexities. Such a conceptual model is what we have called an object model and it is the main subject of this paper. The MADE object model represents a novel approach to multimedia application programming that is founded on the two principal concepts of active objects and delegation. Although these concepts are not novel in themselves, we believe that their combined use in a multimedia development environment represents a substantial enhancement to more traditional approaches to programming in this area.

Abstract Management of the communications among a set of concurrent processes arises in many applications and is a central concern in parallel computing. In this paper we introduce MANIFOLD: a co‐ordination language whose sole purpose is to describe and manage complex interconnections among independent, concurrent processes. In the underlying paradigm of this language the primary concern is not with what functionality the individual processes in a parallel system provide. Instead, the emphasis is on how these processes are interconnected and how their interaction patterns change during the execution life of the system. This paper also includes an overview of our implementation of MANIFOLD. As an example of the application of MANIFOLD, we present a series of small manifold programs which describe the skeletons of some adaptive recursive algorithms that are of particular interest in computer graphics. Our concern in this paper is to show the expressiveness of MANIFOLD, the feasibility of its implementation and its usefulness in practice. Issues regarding performance and optimization are beyond the scope of this paper.

In this paper we describe algorithms for generating NC tool paths for machining of arbitrarily shaped 2 l/2 dimensional pockets with arbitrary islands. These pocketing algorithms are based on a new offsetting algorithm presented in this paper. Our offsetting algorithm avoids costly two-dimensional Boolean set operations, relatively expensive distance calculations, and the overhead of extraneous geometry, such as the Voronoi diagrams, used in other pocketing algorithms.

This paper describes the specification of the GKS input model in Manifold. The aim of the work reported in this paper was two‐fold: first, to review the communication patterns implied by the GKS input model, and second, to evaluate the suitability of the Manifold language as a tool for defining complex dynamic interaction patterns that are common in non‐trivial user interfaces. The GKS input model is also adopted by all more recent ISO graphics standard documents. A more formal scrutiny of the inter‐communication of the components of this model, excluding the implementation details of their functionality, is instructive in itself. It can reveal directions for improvement of its shortcomings and for generalization of its strengths for the ongoing effort to define the functionality of future graphics packages. Manifold is a language for describing inter‐process communications. Processes in Manifold communicate by means of buffered communication links called streams and by reacting to events raised asynchronously by other processes. Our experience shows that Manifold is a promising tool for describing systems of cooperating parallel processes. Our Manifold specification of the GKS input model offers a very flexible way to structure user defined logical input devices. Furthermore, it is simple and modular enough to allow easy extensions to include more functionality by local modifications. As such, it can serve as a basis for possible extensions and enhancements envisioned for future graphics packages. 1987 CR Categories: C.1.2, C.1.3, C.2.m, D.1.3, F.1.2, I.1.3, I.3.6, I.3.4. 1885 Mathematical Subject Classification: 68N99, 68Q10,68U05.

An algorithm for generating tool positions for three-axis mill cutter paths on parametric surfaces is presented. The novelty of this algorithm is in its use of a surface subdivision technique as an alternative to the traditional APT-style iterative approaches based on local tangent-plane extensions. The algorithm presented provides global interference checking and does not exhibit the convergence problems of the traditional approaches.>

A new solid modeling scheme is proposed and developed as the core of an integrated approach to the computer aided design and manufacture of mechanical parts. The benefits of this methodology, which considers the manufacturing process during the design phase, are discussed in the context of an integrated CAD/CAM system.