Rahma Ben Ayed

Uniform verification of workflow soundness

The development of work process-oriented applications in various domains leads to workflow systems where a large number of flow instances run concurrently. A challenging problem is to provide methods for the uniform verification of these parameterized workflows, ie, proving the soundness of the workflow for any number of instances. In this paper, we show the ability of structure theory of Petri nets to conduct a uniform verification for large subclasses of parameterized workflow nets modelling control flow patterns associated with complex synchronization mechanisms, routing constructs and resource allocation constraints. We can take advantage of these results in domains where collaborative activities and competition for resources are preponderant such as agile manufacturing systems, web service applications or grid computing.

Towards the verification and validation of online learning systems: general framework and applications

Online adaptive systems cannot be certified using traditional testing and proving methods, because these methods rely on assumptions that do not hold for such systems. In this paper, we discuss a framework for reasoning about online adaptive systems, and see how this framework can be used to perform the verification of these systems. In addition to the framework, we present some preliminary results on concrete neural network models.

On the verification of business processes by model checking techniques

The correctness of a workflow specification is critical for the automation of business processes. For this reason, errors in the specification should be detected and corrected as early as possible - at specification time. In this paper, we present a verification method for workflow specifications using model checking techniques. We propose an approach for verifying correctness properties of workflow processes using SPIN model checker. First, a formalized workflow specification is translated into a Promela description. Second, the desired property is translated to an LTL formula. Finally, the SPIN model checker is run to check if the correctness properties hold for the model, and, if not, to provide a counterexample.

An adaptive timer for RPL to handle mobility in wireless sensor networks

This paper focuses on the performance of wireless sensor networks characterized by a hybrid topology composed of mobile and static sensor nodes. The Routing Protocol for Low power and lossy networks (RPL), which is standardized as an IPv6 routing protocol for low power and lossy networks, uses the trickle timer algorithm to handle changes in the network topology. However, this algorithm is not well adapted to dynamic environments. This paper enhances the trickle timer in order to fit with mobility requirements. Most of previous works have improved this algorithm without considering the random movement of nodes. In this work, the proposed timer algorithm takes into consideration the random trajectory of mobile nodes, pause time and nodes velocity. It is also dynamically adjusted to prevent from node disconnections. The performance of the modified protocol is evaluated and compared with native RPL, MERPL and RPL with reverse Trickle. The results show that our protocol optimization offers better performance.

Towards the Verification and Validation of Online Learning Adaptive Systems

Online Adaptive Systems in general, and learning neural nets in particular cannot be validated using traditional verification and validation techniques, because they evolve over time, and past learning data influences their behavior. In this paper we discuss a framework for reasoning about online adaptive systems, and see how this framework can be used to perform V\&V on such systems.

RPL protocol adapted for healthcare and medical applications

This paper focuses on wireless sensor networks (WSNs) for healthcare and medical applications which aim to look after patients by monitoring vital signs, diagnostics and drug administrations. WSNs in such applications are usually composed of different types of small-size battery powered sensors. In fact, wearable sensors are used to collect information about the signs of a person that needs a medical care. Static sensors, deployed inside the hospital or the home building, are used to collect information about indoor environment. The collected data is then transmitted towards the sink. Since some patients can move, WSN topology is hybrid and composed of mobile and static nodes. Routing Protocol for Low Power and Lossy Networks (RPL), an IPv6 distance vector routing protocol designed for static wireless sensor network, can be adapted to our need. So in this paper, we propose to modify RPL in order to fit with an hybrid topology. The performance of the modified protocol is evaluated and compared with the existing RPL protocol. The results show that our protocol optimization for healthcare application offers better performance.

A calculus of program adaptation and its applications

Abstract Traditional programming calculi focus on transforming a~specification into a~program. With the advent of such recent paradigms as white box reuse, component-based software development, and re-engineering, and with the continued predominance of software maintenance, less and less software engineering activity nowadays deals with straightforward development. More and more, software products are derived by incrementing, composing, merging, or otherwise modifying existing components. In this paper we present a~calculus that models these paradigms.

Dynamic Data Replication-Driven Model in Data Grids

Today, data grid appears more and more like the future solution of hardware and software offering infinite computing and storage capacity. In order to best exploit the available resources, it seems necessary to design new replication solutions and data movement suited to this type of architecture. It is therefore necessary to adapt the travel policies, positioning and data management based on the needs of applications and the opportunities for the underlying platform to optimize the execution time. The work presented in this paper is a solution to this problem.

Probabilistic verification and evaluation of Backoff procedure of the WSN ECo-MAC protocol

Communication protocols and techniques are often evaluated using simulation techniques. However, the use of formal modeling and analysis techniques for verification and evaluation in particular for Wireless Sensor Networks (WSN) becomes a necessity. In this paper we present a formal analysis of the backoff procedure integrated in the medium access control protocol named ECo-MAC designed for WSN. We describe this backoff procedure in terms of discrete time Markov chains (DTMCs) and evaluated using the well known probabilistic model checker PRISM. After checking the different invariants of the proposed model, we study the effect of contention window length (in number of time contention unit) on the acceptable number of simultaneous senders in a neighborhood of a given receiver. The obtained quantitative results confirm those provided by the simulation using OPNET tool and justify the validity of the adopted value for the time contention unit TCU.

On Service Composition in Cloud Computing: A Survey and an Ongoing Architecture

Cloud computing has become a widely used concept. It is characterized by its elasticity, its on demand services and the unlimited provided resources. However, because of the complexity of customers service requests, their provision became an increasingly difficult task. In fact, in order to meet these requirements, services should be combined to implement a composite one performing the requested task. It is in this sense that the use of SOA architecture, which provides service composition, seems a useful solution. This paper investigates existing works on services discovery and composition in SOA as well as Cloud architectures. We study and compare these works and present an architecture of services composition based on SOA architecture and Cloud computing.