Vangalur S. Alagar

Publishing and discovering context-dependent services

In service oriented computing, service providers and service requesters are main interacting entities. A service provider publishes the services it wishes to make public using service registries. A service requester initiates a discovery process to find the service that meets its requirements using the service registries. Current approaches for the publication and discovery do not realize the essential relationship between the service contract and the conditions in which the service can guarantee its contract. Moreover, they do not use any formal methods for specifying services, contracts, and compositions. Without a formal basis it is not possible to justify through a rigorous verification the correctness conditions for service compositions and the satisfaction of contractual obligations in service provisions. In our recent works, we have identified the role of contextual information, trustworthiness information and legal rules in service provision. This paper focuses on the publication and discovery of trustworthy context-dependent services as supported by the novel framework FrSeC. It introduces a novel ranking algorithm that ranks trustworthy context-dependent services according to the degree they match service requesters requirements. Finally, this paper introduces a prototype implementation for the matching and ranking of services as supported by FrSeC.

A formal approach for the specification and verification of trustworthy component-based systems

Abstract: Software systems are increasingly becoming ubiquitous affecting the way we experience the world. Embedded software systems, especially those used in smart devices, have become an essential constituent of the technological infrastructure of modern societies. Such systems, in order to be trusted in society, must be proved to be trustworthy. Trustworthiness is a composite non-functional property that implies safety, timeliness, security, availability, and reliability. This paper presents a formal approach for the development of trustworthy component-based systems. The approach involves a formal component model for the specification of components structure, functional, and non-functional (trustworthiness) properties, a model transformation technique for the automatic generation of component behavior using the specified structure and restricted by the specified properties, and a unified formal verification method for safety, security, reliability and availability properties using model checking.

Algorithmic motion planning in robotics: Coordinated motion of several disks amidst polygonal obstacles

Given k ≥ 2 circular disks D<inf>1</inf>, D<inf>2</inf>...D<inf>k</inf>in a 2-dimensional region bounded by a finite set of polygonal obstacles, an algorithm to determine the existence of a collision free coordinated motion of the disks is given. The time complexity is shown to be O(n^k} where n is the number of edges composing the walls. This algorithm is believed to be optimal.

A formal framework for design and verification of robotic agents

Intelligent robots are autonomous and are used in environments where human interaction is hazardous or impossible. Verification of software for intelligent robots is mandatory because in situations where intelligent robots are employed online, error recovery is almost impossible. In this paper, we provide a formal framework for offline verification of software used in robotic applications. The specification enables one to design a robotic agent which represents a class of real-life robots. Forward and inverse kinematic operations of the robotic agent are specified using the specification for rigid solids and their primitive operations. An object-oriented design of the robotic agent derived from the specifications is given. We use the specification technique VDM for our purpose.

Context-Aware Security Solutions for Cyber-Physical Systems

The integration of physical systems and processes with networked computing has led to the emergence of a new generation of engineered systems, called Cyber-Physical Systems (CPS). These systems are large networked systems of systems, in which a component system may itself be a grid. In this paper we survey the current state of the art of CPS security, identify the issues surrounding secure control, and investigate the extent to which context information may be used to improve security and survivability of CPS.

A FRAMEWORK FOR DEVELOPING CONTEXT-AWARE SYSTEMS

In ubiquitous computing the environment constraints are often regarded as static and software applications are allowed to function in a mobile ecospace. However, in context-aware systems the environment attributes of software applications are dynamically changing. This dynamism of contexts must be accounted for in order to provide the true intended effect on the application of services. Consequently, context-aware software applications should perceive their context in a continuous manner and seamlessly adapt to it. This thesis investigates the process of constructing context-aware applications and identifies the main challenges in this domain. The two principal requirements are (1) formally defining what context is and expressing the enclosed semantics, (2) formally defining dynamic compositions of adaptations and triggering their responses to changes in the environment context. This thesis proposes a component-based architecture for a Context-aware Framework that would be used to bring awareness capabilities into applications. Two languages are formally designed. One is to formally express situations, leading to a context reasoner, and another is to formally express workflow, leading to timely triggering of reactions and enforcing policies. With these formalisms and a component design that can be formalized, the thesis work fulfills a formal approach to construct context-aware applications. A proof-ofconcept case study is implemented to examine the expressiveness of the framework design and test its implementation.

Functional specification and proof of correctness for time dependent behaviour of reactive systems

A functional formalism for describing and reasoning about the time dependent behaviour of reactive systems is presented. The model is event based and can describe the histories of events with finite duration. It is a generalisation of the model of Caspi and Halbwachs (1986). A set of tools with their operations are introduced in the formalism and structure theorems characterising the algebra of events are proved. The power of this extended model is illustrated through the formal specification and correctness proof for a problem chosen from robotics.

Conformance testing of BDI properties in agent-based software

Agent-based software engineering combines the strengths of agent theory with the practical software engineering methods for developing large intelligent systems. Designing and implementing agent-based systems are complicated tasks because the agents BDI characteristics (beliefs, desires, intentions) when codified in the design/implementation as software characteristics may have acquired different connotations. Consequently testing the reliability of the implementation is equally hard. It is necessary to choose an agents software abstraction that has a minimal deviation from the BDI agent concept, and use it as a formal basis to test an implementation. This paper proposes one such method for conformance testing of BDI properties in an agent-based system.

An Architecture for Managing and Delivering Trustworthy Context-Dependent Services

A precise definition of services is necessary in order to discover, publish, and deliver them. Services, when provided, should satisfy their binding contractual obligations, be seen as trustworthy by the users, and correctly fulfill the needs of the context in which they will be used. The FrSeC architecture proposed in this paper aims to fulfill these needs. The architecture is formally describable, supports the specification, publication, discovery, selection, and composition of services with context-dependent contracts.

Reliability assessment of web applications

The paper discusses a formal approach for specifying time-dependent web applications, and proposes a Markov model for reliability prediction. Measures for predicting reliability are calculated from the formal architectural specification and system configuration descriptions.