Yanik Ngoko

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In this work we study the portfolio problem which is to find a good combination of multiple heuristics to solve given instances on parallel resources in minimum time. The resources are assumed to be discrete, it is not possible to allocate a resource to more than one heuristic. Our goal is to minimize the average completion time of the set of instances,(More)
A challenging task in Web service composition is the runtime binding of a set of interconnected abstract services to concrete ones. This question, formulated as the service selection problem, has been studied in the area of service compositions implementing business processes. Despite the abundance of work on this topic, few of them match some practical(More)
In this paper, we investigate the question of QoS prediction of Web Service Composition (WSC) implementing a business process. We focus on the graph reduction technique and the prediction of the Service Response Time. In the graph reduction technique, we assume that a Web Service Composition can be represented as a graph. The main thesis is that the QoS of(More)
Given a Web Services Composition, we deal with the prediction of the mean service response time that can be expected from a user request that is serviced. This challenge is a key issue in the design of middleware, managing Web Services Composition. We focus on complex services composition that can be described as BPMN choreographies of services. Our main(More)
We propose a new mixed integer linear programming approach to solve the classical problem of scheduling independent parallel tasks without preemption. We propose a formulation where the goal is to minimize the makespan.Then we show the flexibility of this approach by extending the result to the contiguous case. We validate this approach with some(More)
In this paper we deal with the cloud brokering problem in the context of a multi-cloud infrastructure. The problem is by nature a multi-criterion optimization problem. The focus is put mainly (but not only) on the security/trust criterion which is rarely considered in the litterature. We use the well known Promethee method to solve the problem which is(More)
In this paper, we are interested in the service selection problem. In the variant that we consider, the problem's inputs consists of: (1) a services' composition described as an extended business process, (2) a set of concrete services that can be associated with the nodes of the services' composition. The objective is to decide the best mapping between(More)
We can view the topology of classical clouds infrastructures as data centers to which are connected user machines. In these architectures the computations are centered on a subset of machines (the data centers) among the possible ones. In our study, we propose to consider an alternative view of clouds where both users machines and data centers are used for(More)