Lpj Groenewegen

Operational Semantics for Coordination in Paradigm

Paradigm is the modeling language of SOCCA regarding communication, coordination and cooperation. A transition system or STD-based operational semantics for Paradigm is proposed and illustrated with basic producer-consumer examples. The proposed semantics for Paradigm, in contrast to other approaches, provides a sound basis for reasoning about system dynamics and system comparison.

Evolution on-the-fly with paradigm

The coordination language Paradigm allows for a flexible and orthogonal modeling of interprocess relationships at the architectural level. It is shown how dynamic system adaptation can be captured in Paradigm by means of a special evolution component and associated evolution coordination scheme. The component, called McPal, drives the migration following a just-in-time strategy in its own view of the system, independent of other coordination relations. During migration, dynamic consistency between components remains assured, even for mixtures of old, intermediate and new behaviour. A restricted scheme of McPal that supports various forms of self-adaptation is presented. A simple but generic example of a scheduler and workers illustrates on-the-fly updating of coordination and run-time adaptation of scheduling policies using McPal.

Dynamic Consistency in Process Algebra: From Paradigm to ACP

The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at various levels of abstraction. To enable automated verification of Paradigm models, a translation of Paradigm into process algebra is provided. Examples are given and guidelines for a systematic translation into the process algebra ACP are discussed. Verification results building on the mCRL2 toolset are presented as well.

Formalizing Adaptation On-the-Fly

Paradigm models specify coordination of collaborating components via constraint control. Component McPal allows for later addition of new constraints and new control in view of unforeseen adaptation. After addition McPal starts coordinating migration accordingly, adapting the system towards to-be collaboration. Once done, McPal removes obsolete control and constraints. All coordination remains ongoing while migrating on-the-fly, being deflected without any quiescence. Through translation into process algebra, supporting formal analysis is arranged carefully, showing that as-is and to-be processes are proper abstractions of the migrating process. A canonical critical section problem illustrates the approach.

Dynamic consistency in process algebra: From Paradigm to ACP

The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at various levels of abstraction. The operational semantics of Paradigm is given. For a large, general subclass of Paradigm models a translation into process algebra is provided. Once expressed in process algebra, relying on a correctness result, Paradigm models are amenable to process algebraic reasoning and to verification via the mCRL2 toolset. Examples of a scheduling problem illustrate the approach.

Paradigm as Organization-Oriented Coordination Language

Global component behaviours as distinguished in Paradigm, offer the ingredients for specifying inter-component coordination in separation from and consistent with detailed component behaviour. The paper discusses how global behaviours provide great flexibility in arranging computation as well as coordination. In the context of a mediating example we plea for taking such flexibility as an organizational, organic, human-like characteristic; good to have, but usually absent in system specification. In addition, we point out how Paradigms flexibility fits well in the historical perspective of discrete event simulation, modeling, object-orientation and patterns.

Dynamic adaptation with distributed control in Paradigm

Adaptation of a component-based system can be achieved in the coordination modeling language Paradigm through the special component McPal. McPal regulates the propagation of new behavior and guides the changes in the components and in their coordination. Here we show how McPal may delegate part of its control to local adaptation managers, created on-the-fly, allowing for distribution of the adaptation indeed. We illustrate the approach for the well-known example of the dining philosophers problem, by modeling migration from a deadlock-prone solution to a deadlock-free and starvation-free solution without any system quiescence. The system migration goes through various stages, exhibiting a shift of control among McPal and its helpers, and changing degrees of orchestrated and choreographic collaboration. The distributed system adaptation is formally verified using the mCRL2 model checker.

Towards dynamic adaptation of probabilistic systems

Dynamic system adaptation is modeled in the coordination language Paradigm as coordination of collaborating components. A special component McPal allows for addition of new behavior, of new constraints and of new control in view of a new collaboration. McPal gradually adapts the system dynamics. It is shown that the approach also applies to the probabilistic setting. For a client-server example, where McPal adds, step-by-step, probabilistic behavior to deterministic components, precise modeling of changing system dynamics is achieved. This modeling of the transient behavior, spanning the complete migration range from as-is collaboration to to-be collaboration, serves as a stepping stone to quantitative analysis of the system during adaptation.

Distributed adaption of dining philosophers

Adaptation of a component-based system can be achieved in the coordination modelling language Paradigm through the special component McPal. McPal regulates the propagation of new behaviour and guides the changes in the components and in their coordination. Here we show how McPal may delegate part of its control to local adaptation managers, created on-the-fly, allowing for distribution of the adaptation indeed. We illustrate the approach for the well-known example of the dining philosophers problem, by modelling the migration from a deadlock-prone solution to a deadlock-free starvation-free solution without any system quiescence. The adaptation goes through various stages, exhibiting shifting control among McPal and its helpers, and changing degrees of orchestrated and choreographic collaboration.

Towards reduction of Paradigm coordination models

htmlabstractThe coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at a detailed and a global level of abstraction. To enable automated verification of Paradigm models, a translation of Paradigm into process algebra has been defined in previous work. In this paper we investigate, guided by a client-server example, reduction of Paradigm models based on a notion of global inertness. Representation of Paradigm models as process algebraic specifications helps to establish a property-preserving equivalence relation between the original and the reduced Paradigm model. Experiments indicate that in this way larger Paradigm models can be analyzed.