Anne-Elisabeth Baert

A CSP Approach for Metamodel Instantiation

This work is a contribution of Artificial Intelligence to Software Engineering. We present a comprehensive approach to metamodel instantiation using CSP. The generation of models which conform to a given metamodel is a crucial issue in Software Engineering, especially when it comes to produce a variate and large dataset of relevant models to test model transformations or to properly design new metamodels. We define an original constraint modeling of the problem of generating a model conform to a metamodel, also taking into account its additional OCL constraints. The generation process we describe appears to be quicker, more efficient and flexible than any other state-of-the-art approach.

Lifetime in Wireless Sensor Networks

The following paper deals with criterion used to measure communication protocol efficiency in Wireless Sensor Networks. As energy is a crucial characteristic of those networks, it is necessary to pay attention both to the energy consumption and to the distribution of energy consumption, when using communication protocols, so as to increase the lifetime of the whole network. Our aim is to present and discuss criterion designed to analyze communication protocol effectiveness. When designing, for example, communication protocols, it is really important to measure performances with a suitable metric according to our application, else it would be difficult to analyze and to improve a protocol. In this paper, we draw a list of existing criterion, and then introduce two new ones : Average Node Percentage and Monitored Interest Point Percentage. We also point out the relevance regarding the required application for each criterion.

Instantiation of meta-models constrained with OCL: A CSP approach

The automated generation of models that conform to a given meta-model is an important challenge in Model Driven Engineering, as well for model transformation testing, as for designing and exploring new meta-models. Amongst the main issues, we are mainly concerned by scalability, flexibility and a reasonable computing time. This paper presents an approach for model generation, which relies on Constraint Programming. After the translation of a meta-model into a CSP, our software generates models that conform to this meta-model, using a Constraint Solver. Our model also includes the most frequent types of OCL constraints. Since we are concerned by the relevance of the produced models, we describe a first attempt to improve them. We outperform the existing approaches from the mentioned point of view, and propose a configurable, easy-to-use and free-access tool, together with an on-line demonstrator.

Data replication optimisation in grid delivery network

In this paper, we examine the data replication problem in a particular Grid Delivery Network (GDN) which is a system that provides video services, among which is Video On Demand (VOD). In this system, the data are divided into fixed size blocks which must be replicated on hosts to decrease the total download time. We propose a probabilistic model to optimise the average download time of requests based on the hosts availability and the document size distribution. The objective function induced by this model is a non-linear integer problem. It can be solved in real values by Lagrangian optimisation. We prove that in a particular case, this problem can be reduced to a knapsack problem. We propose approximation algorithms and validate them using simulations with varying characteristics.

Dynamic Localized Broadcast Incremental Power Protocol and Lifetime in Wireless Ad Hoc and Sensor Networks

This paper deals with the problem of broadcasting messages and lifetime in wireless ad-hoc and sensor networks. The study is based on the best known localized algorithm, namely LBIP, which is based on a centralized one, BIP, whose principle consists in constructing a broadcast tree rooted on the source node, taking into account the specificities of wireless networks. Even if LBIP has excellent performances regarding energy consumption, it selects for each broadcast the same nodes to retransmit the message; if the source of the broadcast, the base station in a sensor network, is always the same, this will lead to deplete quickly the energy of relay nodes. In this paper, we propose DLBIP, a new localized broadcast algorithm based on LBIP, which dynamically changes the broadcast tree to balance energy consumption on nodes without any additional messages. We show that proposed strategy can significantly increase the number of broadcasts before the network failure. We provide simulations results that clearly demonstrates the lifetime enhancement due to our optimization.