Emna Bouazizi

Management of QoS and data freshness in RTDBSs using feedback control scheduling and data versions

These recent years, a lot of real-time applications are becoming increasingly sophisticated in their data needs, resulting in a greater demand for real-time data services. Real-time database systems (RTDBS) can manage these applications, but the workload in these systems is unpredictable, then RTDBS may become overloaded. A lot of work dealing with quality of service (QoS) has been done to control the transient overshoot. They are based on feedback control real-time scheduling theory. In this paper, we propose a work which allows to execute transactions before their deadlines while using the fresh data. We have extended the feedback-based miss ratio control, by using a multi versions data architecture to guarantee a set of requirements on the behavior of RTDBS and we have considered two data management policies. In the first policy, we have limited the maximum number of data versions and this number is the same for all the data items. In the second policy, the number is dynamically adjusted for each data item.

Multi versions data for improvement of QoS in RTDBS

In current research toward the design of more powerful behavior of RTDBS under unpredictable workloads, different research groups focus their work on QoS (Quality of Service) guarantee. Their research is often based on feedback control real-time scheduling theory. In this paper we propose a technique which allows to execute transactions on time using fresh and precise data while taking into account the global size of the database. We have extended the feedback-based miss ratio control by both using multi-versions data, and proposing a data management policy combining (1) limitation of the versions number and (2) dynamic adjustment of this limit according to a maximum database size parameter.

2LPA-RTDW: A Two-Level data Partitioning Approach for Real-time Data Warehouse

In order to explore the most recent data and react faster to changes of business conditions, organizations consider Real-Time Data Warehousing (RTDW) as a powerful technique to achieve OLAP (On Line Analytical Processing) analyses and business intelligence (BI). OLAP analyses are complex since they query several relational tables with huge volumes. In order to deal with this volumetry, several optimization techniques have been proposed in the literature as materialized views and data partitioning. Partitioning is an effective method to increase query efficiency in a data warehouse. This paper proposes a novel data partitioning approach for real-time data warehouse, called 2LPA-RTDW (Two-Level data Partitioning Approach for Real-Time Data Warehouse) by allowing unbalance of data amount in each partition while taking into account user requirements. We have evaluated the proposed approach using the new TPC-DS1 benchmark; the preliminary results show that the approach is quite interesting.

A new QoS Management Approach in real-time GIS with heterogeneous real-time geospatial data using a feedback control scheduling

Geographic Information System (GIS) is a computer system designed to capture, store, manipulate, analyze, manage, and present all types of spatial data. Spatial data, whether captured through remote sensors or large scale simulations becomes more and big and heterogenous. As a result, structured data and unstructured content are simultaneously accessed via an integrated user interface. The issue of real-time and heterogeneity is extremely important for taking effective decision. Thus, heterogeneous real-time spatial data management is a very active research domain nowadays. Existing research are interested in querying of real-time spatial data and their updates without taking into account the heterogeneity of real-time geospatial data. In this paper, we propose the use of the real-time Spatial Big Data and we define a new architecture called FCSA-RTSBD (Feedback Control Scheduling Architecture for Real-Time Spatial Big Data). The main objectives of this architecture are the following: take in account the heterogeneity of data, guarantee the data freshness, enhance the deadline miss ratio even in the presence of conflicts and finally satisfy the requirements of users by the improving of the quality of service (QoS).

Applicability of the (m,k)-firm Approach for the QoS Enhancement in Distributed RTDBMS

Many real-time applications are geographically distributed and have to use large amounts of real-time data. Using DRTDBMS is increasingly needed to better manage the large amount of real-time data. In order to take into account unpredictable workload, Quality of Service (QoS) based approaches are the most appropriate. In the particular case of distributed applications, it is necessary to consider the problems of load balancing for user transactions between different sites. Feedback Scheduling approaches can adapt to unpredictable workload variations. In this paper, we propose to apply a (m,k)-firm approach to schedule user transactions in a distributed feedback scheduling architecture. We also show that our approach can significantly improve the performance of existing approaches by increasing the number of transactions that meet their deadlines while maintaining the DRTDBMS in a stable state.

An Ontological Approach to Design Real-time Applications

These recent years, we have seen the emergence of several studies allowing a linkage between databases and ontologies to facilitate the design of databases. However, these studies do not address the needs of the advanced applications, because they do not integrate mechanisms that consider the temporal characteristic. In addition, the complexity of real-time applications is ever increasing which makes their design processes very difficult. For that purpose, a new vision will allow to fill in the limits of these studies and to suggest a method to conceptualize this kind of databases (real-time databases). This vision needs to define a new ontology to be integrated into these databases. This suggested ontology should be used to represent a domain in an explicit way without any ambiguity, to describe the most general categories and relations, and to define the temporal information and to resolve the semantic conflicts. In this paper, our solution is to advance an ontological modeling for real-time applications.

Phenotypic and Molecular Characterization of Verticillium dahliae , the Causal Agent of Verticillium Wilt of Olive in Tunisia

Aims: During the last two decades, verticillium wilt of olive has spread to young olive orchards were it causes severe yield losses and death of olive trees in southern and central regions of Tunisia. Therefore, identification of the causal agent as well as the study of its pathogenicity will be useful for design the appropriate management program. Place and Duration of Study: This work was performed in the Laboratory of Phytopathology at the Olive Tree Institute (Sfax, Tunisia) between July 2014 and June 2015. Original Research Article Gharbi et al.; JALSI, 4(3): 1-8, 2016; Article no.JALSI.23696 2 Methodology: This study was conducted using phenotypic and molecular methods to identify the causal agent of the decline and death of olive trees. The pathogen was recovered from infested tissues using a potato dextrose agar medium. Identity of the isolates was confirmed by ITS-RFLP and sequencing. Pathogenicity of the isolates was evaluated by infection bioassay on young olive plants. Results: All the fungal isolates were hyaline, flocculose and produced microsclerotia after 15 days of incubation at 25°C, which is in agreement with the identification key of Verticillium species. All the isolates were characterized by ITS-RFLP and sequencing of the internal transcribed spacer. All the isolates produced 470 bp using primers ITS1/ITS4. Digestion of the ITS product using EcoRI and HaeIII produced two fragment of 250 and 220 bp and three fragment of 300, 150, and 20 bp respectively. Pathogenicity was evaluated on two-year old olive plants using an artificial infection bioassay. After 15 days of inoculation, similar symptoms were produced as natural infection. Symptoms of wilt developed rapidly and caused the death of more than 50% of the inoculated plants. Conclusion: V. dahliae is present in almost all growing olive regions of Tunisia. However, local V. dahliae populations in Tunisia is predominated by a highly pathogenic clone which is able to overcome the resistance of the main olive cultivar.

Molecular Epidemiology of Verticillium Wilt of Olive in Southern and Central Tunisia: Evidence of Host Adaptation Hypothesis

Aims: During the last two decades, verticillium wilt of olive has spread to young olive orchards where highly susceptible crops such as potato, watermelon and tomato are cultivated near to olive orchards. It was therefore hypothesized that there is an adaptation phenomenon that drives the pathogenicity of V. dahliae in order to infect a broad range of hosts. Therefore, it will be useful to identify the factors that increase the severity of the pathogen which helps growers to implement the appropriate crop rotation program. Place and Duration of Study: This work was performed in the Laboratory of Phytopathology at the Original Research Article

Scheduling Approach for Enhancing Quality of Service in Real-Time DBMS

Applications are increasingly characterized by manipulating large amounts of data and by time constraints to which are submitted data and treatments. RTDBMSs (Real-Time DataBase Management Systems) are an appropriate formalism to handle such applications. However, a RTDBMS often goes through overload periods following the unexpected arrival of user transactions. During such periods, transactions are more likely to miss their deadlines and that directly affects the QoS (Quality of Service) provided to users. Thus, our work is to propose a new scheduling protocol to optimize the execution of transactions without exceeding their deadlines. It consists on assigning priorities to transactions based both on their deadlines, their arrival dates and their priority levels defined by users. Also, we show that our approach can maximize the number of successful transactions, in particular those classified as critical for users. The obtained results are compared with conventional scheduling approaches.