Riad Mokadem
Paul Sabatier University
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Publication
Featured researches published by Riad Mokadem.
International Journal of Grid and Utility Computing | 2015
Riad Mokadem; Abdelkader Hameurlain
Replicating for performance constitutes an important issue in large-scale data management systems. In this context, a significant number of replication strategies have been proposed for data grid systems. Some works classified these strategies into static vs. dynamic or centralised vs. decentralised or client vs. server initiated strategies. Very few works deal with a replication strategy classification based on the role of these strategies when building a replica management system. In this paper, we propose a new replication strategy classification based on objective functions of these strategies. Also, each replication strategy is designed according to the data grid topology for which it was proposed. We point out the impact of the topology on replication performance although most of these strategies have been proposed for a hierarchical grid topology. We also study the impact of some factors on performance of these strategies, e.g. access pattern, bandwidth consumption and storage capacity.
information integration and web-based applications & services | 2010
Riad Mokadem; Abdelkader Hameurlain; A Min Tjoa
Using Distributed Hash Tables (DHT) for resource discovery in large-scale systems generates considerable maintenance overhead. This not only increases the bandwidth consumption but also affect the routing efficiency. In this paper, we deal with resource discovery while minimizing maintenance overhead in hierarchical DHT systems. The considered resources are metadata describing the data sources. In our solution, only one gateway in one overlay is attached to the superior level overlay. It aims to reduce both lookup and maintenance costs while minimizing the overhead added to the system. We present a cost analysis for a resource discovery process and discuss capabilities of the proposed protocol to reduce the overhead of maintaining the overlay network. The analysis result proved that our design decrease significantly the maintenance costs in such systems especially when nodes frequently join/leave the system.
international conference on data management in grid and p2p systems | 2011
Imen Ketata; Riad Mokadem; Franck Morvan
This paper deals with resource discovery in data Grid environments while taking into account the semantic heterogeneity of data sources. A domain ontology is associated to each domain and mappings exist between these domain ontologies. Our resource discovery method is adapted to any mapping graph topology between domain ontologies provided that the graph is connected. The proposed addressing system allows permanent access from any domain ontology to another despite the dynamicity of nodes. The performance evaluation of the proposed method proved the discovery cost reduction especially for inter-ontology queries. They also provide a significant maintenance costs reduction of such system especially when peers frequently join / leave the system.
International Journal of Information Systems and Social Change | 2017
Sean B. Eom; Khaoula Tabet; Riad Mokadem; Mohamed Ridda Laouar
This paper presents a survey of data replication strategies in cloud systems. Based on the survey and reviews of existing classifications, we propose another classification of replication strategies based on the following five dimensions: i static vs. dynamic, ii reactive vs. proactive workload balancing, iii provider vs. customer centric, iv optimal number vs. dynamic adjustment of the replica factor and v objective function. Ideally, a good replication strategy must simultaneously consider multiple criteria: i the reduction of access time, ii the reduction of the bandwidth consumption, iii the storage resource availability, iv a balanced workload between replicas and v a strategic placement algorithm including an adjusted number of replicas. Therefore, selecting a data replication strategy is a classic example of multiple criteria decision making problems. The taxonomy we present can be a useful guideline for IT managers to select the data replication strategy for their organization.
ubiquitous intelligence and computing | 2016
Uras Tos; Riad Mokadem; Abdelkader Hameurlain; Tolga Ayav; Sebnem Bora
In todays world, tenants of cloud systems expect timely responses to queries that process ever-increasing sizes of data. However, most cloud providers offer their services without any performance guarantees to their tenants. In this paper we propose a data replication strategy that aims to satisfy performance guarantees for the tenant while ensuring profitability of the cloud provider. Our strategy estimates the response time of the queries, as well as the expenditures that affect the profitability of the cloud provider. The decision of whether to perform replication is determined by the fulfillment of these two criteria. Validity of the proposed strategy is provided by means of a simulation study.
Intech | 2011
Imen Ketata; Riad Mokadem; Franck Morvan
Informatics application in biomedicine accumulates large amount of data constituting a big data source network. These sources are highly heterogeneous, dynamic and distributed in large scale environments. Resource discovery in such environments presents an important step for the SQL-query processing. Many research studies have focused on this issue. However, structural heterogeneity problems have been more widely studied than semantic ones. In this paper, we deal with the resource discovery in large-scale environments (as data grid systems) considering data semantic heterogeneity of biomedical sources. The main advantages of the proposed resource discovery method are: (i) allowing a permanent access, through an addressing system, from any domain ontology DOi to another DOj (inter-domain discovery) despite peers’ dynamicity, (ii) reducing the maintenance cost and (iii) taking into account the semantic heterogeneity.
Cluster Computing | 2018
Uras Tos; Riad Mokadem; Abdelkader Hameurlain; Tolga Ayav; Sebnem Bora
Cloud computing is a relatively recent computing paradigm that is often the answer for dealing with large amounts of data. Tenants expect the cloud providers to keep supplying an agreed upon quality of service, while cloud providers aim to increase profits as it is a key ingredient of any economic enterprise. In this paper, we propose a data replication strategy for cloud systems that satisfies the response time objective for executing queries while simultaneously enables the provider to return a profit from each execution. The proposed strategy estimates the response time of the queries and performs data replication in a way that the execution of any particular query is still estimated to be profitable for the provider. We show with simulations that how the proposed strategy fulfills these two criteria.
extended semantic web conference | 2012
Riad Mokadem; Franck Morvan; Abdelkader Hameurlain
Most of the existing hierarchical Distributed Hash Table (DHT) systems, used for a resource discovery, generate considerable maintenance overhead which affects the routing efficiency in large scale systems. In this paper, we propose a Scalable Distributed Data Structures (SDDS) based Hierarchical DHT (SDDS- HDHT) solution for an efficient data source discovery in data Grid systems. Our solution deals with a reduced number of gateway peers running a DHT protocol. Each of them serves also as a proxy for second level peers in a single Virtual Organization (VO), structured as a SDDS. The performance evaluation of the proposed method proved the discovery cost reduction especially for intra-VO resource discovery queries. It also proved significant system maintenance save especially when peers frequently join/ leave the system.
International Journal of Adaptive, Resilient and Autonomic Systems | 2012
A Min Tjoa; Riad Mokadem; Abdelkader Hameurlain
Despite hierarchical Distributed Hash Table (DHT) systems have addressed flat overlay system problems, most of existing solutions add a significant overhead to large scale systems. This not only increases the bandwidth consumption but also affect the routing efficiency. This paper deals with a resource discovery while minimizing maintenance overhead in hierarchical DHT systems. The considered resources are metadata describing data sources. In the solution, only one gateway in one overlay is attached to the superior level overlay. It aims to reduce both lookup and maintenance costs while minimizing the overhead added to the system. The authors present a cost analysis for a resource discovery process and discuss capabilities of the proposed protocol to reduce the overhead of maintaining the overlay network. The analysis result proved that our design decrease significantly the maintenance costs in such systems especially when nodes frequently join/leave the system.
The Journal of Supercomputing | 2015
Uras Tos; Riad Mokadem; Abdelkader Hameurlain; Tolga Ayav; Sebnem Bora