Hacène Fouchal

Regression Testing Web Services-based Applications

Web applications can be composed of heterogeneous selfcontained web services. Such applications are usually modified to fix errors or to enhance their functionality. After modifications, regression testing is essential to ensure that modifications do not lead to adverse effects. In this paper, we present a safe regression testing algorithm that selects an adequate number of non-redundant test sequences aiming to find modification-related errors. In our technique, a web application and the behavior of its composed components are specified by a two-level abstract model represented as a Timed Labeled Transition System. Our algorithm selects every test sequence that corresponds to a different behavior in the modified system. We discuss three situations for applying this algorithm: (1) connecting to a newly established web service that fulfills a composed web service, (2) adding or removing an operation in any of the composed web services, (3) modifying the specification of the web application. Moreover, modifications handled by the algorithm are classified into three classes: (a) adding an operation, (b) deleting an operation, (c) fixing a condition or an action. Key-words : label transition systems, testing, verification, web service, web application.

A simple approach for testing web service based applications

The cost of developing and deploying web applications is reduced by dynamically integrating other heterogeneous self-contained web services. However, the malfunctioning of such systems would cause severe losses. This paper presents a technique for building reliable web applications composed of web services. All relevant web services are linked to the component under test at the testing time; thus, the availability of suitable web services is guaranteed at invocation time. In our technique, a web application and its composed components are specified by a two-level abstract model. The web application is represented as Task Precedence Graph (TPG) and the behavior of the composed components is represented as a Timed Labeled Transition System (TLTS). Three sets of test sequences are generated from the WSDL files, the TLTS and the TPG representing the integrated components and the whole web application. Test cases are executed automatically using a test execution algorithm and a test framework is also presented. This framework wraps the test cases with SOAP interfaces and validates the testing results obtained from the web services.

Joint routing and location-based service in VANETs

Geographic routing protocols use location information when they need to route packets. In the meantime, location information are maintained by location-based services provided by network nodes in a distributed manner. Routing and location services are very related but are used separately. Therefore, the overhead of the location-based service is not considered when we evaluate the geographic routing overhead. Our aim is to combine routing protocols with location-based services in order to reduce communication establishment latency and routing overhead. Our main contribution is to reduce the location overhead. Thus, we propose two combinations: (1) a geographic routing protocol with GLS called Hybrid Routing and Grid Location Service (HRGLS) and (2) a geographic routing protocol with HLS denoted Hybrid Routing and Hierarchical Location Service (HRHLS), where instead of launching an exact position request, we send the packet to the old destination position and when the packet is approaching the former position, we request the exact one. The complexity of the location query cost in both proposed schemes is O(logN), while it is O(N) in the case of HLS and GLS. Simulation results also confirm the complexity analysis and show promising results in terms of latency, packet delivery ratio and control message overhead.

A Comparison of Reactive, Grid and Hierarchical Location-Based Services for VANETs

VANETs (Vehicular Ad-hoc NETworks) are a special case of MANETs (Mobile Ad-hoc NETworks). Their main feature is the high mobility range of nodes, which causes topology changes and frequent disconnections. Topology-based routing protocols have weak performances in such networks. This is why a new set of routing protocols, designated as geographic routing protocols, were designed to enhance performances and ensure a better scalability. These geographic protocols assume on one hand that all nodes must be aware about their position (by using a positioning system like GPS). On the other hand they also assume a certain knowledge about the position of the destination node and the position of their neighbors thanks to Location-based Services. In this paper, we compare three location-based services: Reactive Location Service (RLS), Grid Location Service (GLS) and Hierarchical Location Service (HLS) while coupled to the well known geographic routing protocol Greedy Perimeter Stateless Routing (GPSR). As far as we know, our work is the first that targets the performance evaluation of location-based services while coupled with a routing protocol. The simulations were performed using the NS-2 simulator on a realistic map about the city of Reims (France). Besides, a scalability study of GLS and HLS is presented. This study is based on three qualitative metrics (the location maintenance cost, the location query cost and the storage cost).

Slot scheduling for wireless sensor networks

In wireless sensor networks WSN, one of the most important challenges is power saving, then various contributions are suggested since a decade. In this paper, we propose a distributed and adaptive gossiping technique able to guarantee communications over all sensors and to save a high amount of energy. The aim is to allow to the network to achieve a self-organizing procedure in order to provide an efficient structuring approach for communications over all sensors. The medium access will be TDMA Time Division Medium Access like. Indeed, each sensor will have a particular slot for listening and another one for sending. The slot assignment is achieved in a distributed manner and is continuously reconfigurable. That means when a sensor leaves the network, its assigned slot will be recovered and when a new one wants to join the network, the last available slot will be assigned to it.

A mobile wireless body area network platform

Abstract This paper aims to propose a system architecture for a mobile health-monitoring platform based on a wireless body area network (WBAN). We detail the WBAN features from either hardware and software point of view. The system architecture of this platform is three-tier system. Each tier is detailed. We have designed a flowchart of a use of the WBANs to illustrate the functioning of such platforms. We show the use of this platform in a wide area to detect and to track disease movement in the case of epidemic situation. Indeed, tracking epidemic disease is a very challenging issue. The success of such process could help medical administration to stop diseases quicker than usual. In this study, WBANs deployed over volunteers who agree to carry a light wireless sensor network. Sensors over the body will monitor some health parameters (temperature, pressure, etc) and will run some light classification algorithms to help disease diagnosis. Finally, the WBAN will send aggregated data about the disease to some base stations which collect the results. Our platform will run an on-line disease tracking program and to detect some information about how the disease is propagated.

HHLS: A hybrid routing technique for VANETs

In this paper, we propose a combination between a routing protocol Greedy Perimeter Stateless Routing (GPSR) and Hierarchical Location Service (HLS) that we denote Hybrid Hierarchical Location Service (HHLS). HLS and GPSR used to be combined in the original work with a direct method, i.e. GPRS takes care of routing packets and HLS is called to get the destination position when the target node position is not known or is not fresh enough. When a destination is quite far away from the sender, the exact position of the target is calculated, and an extra overhead is generated from sender to receiver. Our main purpose is to reduce this overhead in HHLS. We suggest to proceed as follows: when a packet has to be sent to the destination, it will be sent directly to the former position of the target instead of requesting for the exact position. When the packet is approaching the former position, the exact position request is then sent. We have proposed a patch over the NS-2 simulator for HHLS according to our proposal. We have conducted experimentations which show promising results in terms of latency, packet delivery rate and overhead.

A low energy consumption MAC protocol for WSN

The design of an energy-efficient Medium Access Control (MAC) protocol is one of the major issues in wireless sensor networks (WSN). In this study, we present a MAC protocol adapted to a particular class of WSNs. This protocol is mainly used for nodes located in the same radio range. It could be used by WSNs dedicated to environment monitoring where each node senses a parameter periodically. In this particular case, a node executes a code during a small period and in the rest of the time it moves to a sleeping mode. Our protocol maintains a abstract ring which ensures the ordered communications and avoids collisions. The actual version of the technique is one-hop based communication. The multi-hop extension is discussed in the paper.

PHRHLS: A movement-prediction-based joint routing and Hierarchical Location Service for VANETs

Location-based services provide (and maintain) location information used by geographic routing protocols. Routing and location service are widely related, but handled separately in usual studies about Vehicular Ad hoc Network (VANET). In this paper, we propose a hybrid approach, denoted mobility-Prediction-based Hybrid Routing and Hierarchical Location Service (PHRHLS), coupling a VANET routing protocol, the Greedy Perimeter Stateless Routing (GPSR), and the Hierarchical Location Service (HLS) extended with a mobility prediction algorithm. We show that our approach, PHRHLS, reduces the localization overhead and enhances the routing performances. Indeed, our extensive simulations show promising results in terms of end-to-end latency, packet delivery ratio and control message overhead.

Distributed backtracking algorithm based on tree decomposition over wireless sensor networks

In this paper, we propose a methodological approach to solve distributed nonbinary constraint satisfaction problem (CSP) on wireless sensor networks (WSNs). A distributed CSP is a CSP in which variables and constraints are distributed among multiple agents. On WSNs, it is usual to handle applications that need to solve distributed problems. Different real‐world applications can be modeled as distributed CSPs, and numerous algorithms based on enumerative search have been proposed to solve them. The most cited one is distributed backtracking algorithm in which each variable is associated to each agent. This algorithm is known as fine‐grained distributed algorithm. All the search efforts of this algorithm concerns the communication between agents that are very expensive. In addition, this approach is not realistic because, in general, an agent might control more than one variable. In this paper, we propose a generic methodology for developing coarse‐grained backtracking algorithm. Mainly, a preprocess technique breaks a single large problem into a set of smaller connected ones. These semi‐independent CSPs can be efficiently and concurrently solved and can cooperate to solve the whole problem. We illustrate the preprocess technique by the tree decomposition method for its good theoretical properties. The aim of our paper is to present an efficient approach to solve complex distributed CSPs over WSNs. Copyright