Abdelghani Benharref

Performance Evaluation of Mobile Web Services

Due to the advances on mobile technology, it is becoming feasible to host Web Services on a mobile device, making it perceived as potential data collector and provider. Hosting Web Services on mobile devices gains in importance when it comes to deliver real-time contextual data, such as current location or real-time heart rate. In addition to the characteristics of the available network, the usability of the Mobile Host depends on computational resources of the device itself. Currently, some emerging lightweight frameworks to host web services on mobile devices have been developed. They are recognized for their low resources footprint but they are barely tested. Consequently, the potential of utilizing them in real life settings is not known yet. In this paper, we address this issue and we propose to test the performance of Web Services hosted on mobile devices. We first propose an architecture that allows the deployment of Web Services on mobile devices. The architecture implements an important feature that provides the possibility of resuming and managing the connection state when disconnections happen. Then, we identify and evaluate the QoS of these web services such as response time, availability, throughput, and scalability. We also evaluate the overall performance of the mobile device host with main focus on the battery consumption. We applied our experiments to both SOAP and RESTful Web Services. The results we have obtained are promising and confirm the fact that RESTful Web Services are more convenient for mobile devices as their QoS does not degrade considerably and is kept at a satisfactory level. It also proves the potential hosting of Web Services on current mobile devices with acceptable battery consumption.

Efficient traces' collection mechanisms for passive testing of Web Services

Web Services are a novel approach for business-to-business interactions. Their management, especially fault and performance management, is becoming necessary for their success and emergence. Nowadays, this management is platform-dependent and does not allow third parties to be involved. In this paper, we consider management of Web Services by passive testing where the tester itself is a Web Service. We propose different architectures for observation of simple and composite Web Services. We also study a set of online traces collection mechanisms and discuss their performances in terms of required CPU/RAM resources and introduced network overhead. These performances are then maximized by selecting best locations of observers. Observation considers both functional and non-functional (QoS) properties of Web Services. The paper presents also our experiments using different observation architectures and traces collection mechanisms while observing a simple and a composite Web Service.

New approach for EFSM-based passive testing of web services

Fault management, including fault detection and location, is an important task in management of Web Services. Fault detection can be performed through testing, which can be active or passive. Based on passive observation of interactions between a Web Service and its client, a passive tester tries to detect possible misbehaviors in requests and/or responses. Passive observation is performed in two steps: passive homing and fault detection. In FSM-based observers, the homing consists of state recognition. However, it consists of state recognition and variables initialization in EFSM-based observers. In this paper, we present a novel approach to speed up homing of EFSM-based observers designed for observation of Web Services. Our approach is based on combining observed events and backward walks in the EFSM model to recognize states and appropriately initialize variables. We present different algorithms and illustrate the procedure through an example where faults would not be detected unless backward walks are considered.

Towards the testing of composed web services in 3 rd generation networks

With the proliferation of web services in business and as the number of web services is increasing, it is anticipated that a single web service will become insufficient to handle multitude, heterogeneous, and complex functions. Hence, web service composition will be used to create new value added services with a wide range of functionalities. Management of a composed web service is a complex issue compared to the management of a non-composed (basic) web service. In this paper, we propose a multi-observer architecture for detecting and locating faults in composed web services. It makes use of a network of observers that cooperate together to observe a composed web service. An observation strategy based on a set of heuristics is presented to reduce the number of web services to be observed. Observers are developed as mobile agent observers to help reducing the load introduced by the observation. Algorithms for fault detection, notification, and collaboration between observers are described. Finally, the architecture is illustrated through a case study for observing a composed teleconferencing web services in a 3G network. Different components of the architecture are developed. The network load introduced by the observation is measured and the fault detection capabilities of the architecture are discussed.

Mobile agents for testing web services in next generation networks

Web services are emerging as the standard paradigm for program-to-program interactions on Internet. They are gaining more and more momentum and are expected to play a key role in Next Generation Networks. For these reasons, their management is becoming critical. Fault management is one of the most challenging areas of network and service management. It includes fault detection, isolation and repair. This paper proposes a Web service-based architecture for detecting faults in Web services. The architecture is rooted in passive testing. Passive testing consists of observing and analyzing messages the component under test exchanges with its environment. The passive testers of our architecture are designed as Web services. The components of the architecture are presented and the potential interfacing technologies are evaluated. This evaluation has led us to the selection of mobile agents.

On the Verification of Behavioral and Probabilistic Web Services Using Transformation

In this paper, we propose a preliminary approach for automating web service verification. We use Semantic Markup for Web Services (OWL-S) to describe web service behavior. We parse the OWL-S file and transform it automatically to a corresponding Markov chain diagram or Markov decision process, which are then transformed to a PRISM model to be used as input by PRISM, a probabilistic model checker, to verify automatically the web service behavior. We provide an implementation of the transformation algorithm through a developed software tool automating all the transformation and verification activities.

A New Approach for Quality Enforcement in Communities of Web Services

Nowadays, Web Services are considered as de facto and attracting distributed approach of application/services integration over the Internet. Web Services can also operate within communities to improve their visibility and market share. In a community, Web Services usually offer competing and/or complementing services. In this paper, we augment the community approach by defining a specific-purpose community to monitor Web Services operating in any Web Services community. This monitoring community consists of a set of Web Services capable of observing other Web Services. Clients, providers, as well as managers of communities can make use of the monitoring community to check if a Web Service is operating as expected. This paper defines the overall architecture of the monitoring community, the business model behind, different rules and terms to be respected by its members, services it offers to its various classes of customers. The paper also presents promising experimental results using the monitoring community.

VAQoS: Architecture for End-to-End QoS Management of Value Added Web Services

During the last few years, Value Added Web Services (VAWS) are increasingly becoming a hot issue in both research and industry. With the abundance of VAWS providers, Quality of Service (QoS) is a key factor to allow potential clients to differentiate between providers. In this paper, we propose a new architecture, called VAQoS, for managing and assuring QoS provision for VAWS. This architecture performs management of QoS by: (1) allowing providers to extend the service description with QoS-centered annotations, (2) including a validation process that enables providers to test their service interfaces as well as the level of QoS they can provide prior to publishing the service, (3) allowing clients to express their required functionalities with QoS requirements; (4) providing support for QoS negotiation between clients and providers, (5) allowing monitoring of the agreed QoS between clients and providers, and therefore, detecting any QoS violation; (6) providing an application programming interface that shields the application of the provider and client from the complexity of managing QoS specification, QoS publication, and QoS discovery. A first prototype of VAQoS is developed.

Towards a best-effort framework for developing smart mobile applications

Despite the rapid growth of the mobile technology, mobile devices are still considered as resource constrained with limited battery. Same computations are awkward to be undertaken on these devices with limited processing capabilities. Other processes are costly in terms of battery consumption. Ideally, mobile applications will have the possibility to decide either to do a computation locally or remotely depending on the current device capabilities status. Making such decision is very challenging as many interrelated factors are to be considered (e.g. network connection, battery level, and processing capabilities). In this paper, we propose a framework that supports developers in implementing such smartness fitness within their mobile applications. This solution provides approaches in form of algorithms to instrument code of mobile applications to behave in smart way. Incorporating these algorithms will allow for on-the-fly decision of local versus remote computation using a calculated cost function. We conducted some experimental scenarios to evaluate the usability and effectiveness of our decision-based algorithms. The results we have obtained prove that for the same computation, depending on the size of data, the network status and the device status, the decision of the engine may differ.

Mobility-Aware Selection of Mobile Web Services

Quality of Web Service (QoWS) support for Mobility-aware Web services (MWS) is critical for mobile users since it relies on the available resources on mobile devices consuming these services. In this paper, we propose a selection model for MWS based on QoWS and device resources requirements. The main purpose of the model is to support the client in selecting MWS based on desired QoWS as well as on its device resources availability. We propose a verification scheme to verify the conformity of claimed MWS QoWS and required device resources compared to the published one. The verification is used to support selection of MWS. The implementation of our model is discussed and the importance of our verification scheme is highlighted.