Yassine Ouhammou

Reducing the gap between design and scheduling

Model-based design techniques for real-time systems have limited real-time expressiveness, focusing their abilities to classic scheduling models (like the classic sporadic model) and to a reduced set of temporal analysis techniques (like the Rate Monotonic Analysis). Moreover, to perform analysis with the real-time scheduling theory, the system designers must check that their models are compliant with the assumptions of this theory. This article introduces an open meta-model, based on model-driven engineering, which aims to cover new real-time scheduling models and techniques. Therefore, it will be possible to connect several independent schedulability analysis tools, following closely the advances in real-time scheduling theory, dealing with a temporal model that will be covered by our meta-model. This connection can be done at different stages of the design (early for sensitivity analysis, at a later stage for temporal validation) to create a temporal model of the designed system, and to assist the designer who is not necessarily an expert in scheduling theory. This paper can be considered as an attempt to motivate the real-time community to have a taxonomy of real-time scheduling models, problems and analysis techniques.

Model Driven Timing Analysis for Real-Time Systems

This paper stresses the difficulty for a system designer to use an appropriate real-time task model for his system, and to choose the associated scheduling analysis tests/dimensioning techniques. We propose a model-based approach tackling this difficulty. We focus on the schedulability analysis tree used by our method in order to help the designer to dimension, and then to validate his system.

CostDL: A Cost Models Description Language for Performance Metrics in Database

The development of database systems and applications requires the use of metrics to evaluate the quality and the efficiency of each phase, especially as regards the physical phase, where logical, physical and hardware optimizations are mainly used. Since the 1980s, a large range of cost models has been proposed. Each cost model is dedicated to the calculation of specific metrics and mainly pertains to specific target database, the workload, Database Management Systems (DBMS), deployment platforms, etc. Augmenting and improving reuse in complex systems is increasingly recognized as a crucial as it contributes to increasing the quality of the target systems, shortening engineering development time, and to paring down costs for the engineering of typically highly customer-specific solutions. In this paper, we propose a cost models language called CostDL that allows the description of metrics related to the most sensitive database system characteristics. An implementation of CostDL and its usage through a running example are also provided.

Towards a simple meta-model for complex real-time and embedded systems

We introduce an open meta-model that will be easily enriched to cover new real-time scheduling models and techniques. On the one hand, it will be possible to connect several independent schedulability analysis tools, following closely the advances in real-time scheduling theory, dealing with a temporal model that will be covered by our metamodel. On the other hand, we will use model transformation techniques in order to extract information from different design methodologies. This extraction can be done at different stages of the design (early for sensitivity analysis, at a later stage for temporal validation) to create a temporal model of the designed system, without the designer to be an expert in scheduling theory. We are working currently on the meta-model phase. The objective is to cover enough concepts to be able to represent a big part of the real-time scheduling models and problems, without introducing too much complexity. This paper uses the UML profile mechanism to describe such a meta-model.

More transparency in testing results: Towards an open collective knowledge base

We are currently witnessing an explosion of advances in database technology, that cover all phases of database application design: non-functional requirements, conceptual modeling, logical modeling, deployment, physical design and exploitation. Researchers and engineers cooperate to integrate these advances in the database design. Their proposed solutions have to be confronted with similar studies whose results have been either published in scientific papers or on specific websites such as that of TPC (the Transaction Processing Council). Recently, several researchers have highlighted difficulties in reproducing the results of existing studies. As a consequence, certain research communities require that the environment and the results of the testing activities have to be published in order to facilitate their reproduction, to publish their simulator environments, in order to allow evaluators to perform by their own the experiments. This is quite similar to the Volkswagen fake pollution controls scandal. In this paper, we firstly, advocate the transparency of testing in the database field. Secondly, we propose the use of a repository dedicated to store testing environment and results. The environment includes used data sets, deployment platform, non-functional requirements, used algorithms, hypotheses, etc. and the results completed with their measurement units.

A Meta-advisor Repository for Database Physical Design

The physical design is one of the crucial phases of advanced database design life cycle. This is due to its important role in selecting optimization structures such as materialized views, indexes, and partitioning to speed up the performance of queries. This phase has been amplified by the continually needs of storing and managing in efficient way the deluge of data in storage systems. This situation motivates the editors of commercial and non-commercial Database Management Systems (e.g. SQL Tuning Advisor - Oracle and Parinda - PostgreSQL) to propose tools (called advisors) to assist database administrators in their tasks when selecting their relevant optimization structures for a given database/data warehouse schema and a workload. The maturity of research performed in the physical design motivates us to go further and capitalize the knowledge and expertise in terms of processes, the algorithms, the cost models used to quantify the benefit of the selected optimization structures, etc. used by the research community. In this paper, we first propose a physical design language called PhyDL that allows describing all inputs and outputs of the physical design phase. Secondly, to increase the reuse of the existing advisors, we elaborate a repository called Meta-Advisor that persists all components of the physical design. Finally, a case study of our contribution is presented to stress the meta-advisor repository and highlights its importance.

A Recommender System for DBMS Selection Based on a Test Data Repository

Nowadays, we see an explosion in the number of Database Management Systems (DBMS) in the market. Each one has its own characteristics. This spectacular development of DBMS is mainly motivated by the need for storing and exploiting the deluge of heterogeneous data for analytical purposes. As a consequence, companies and users are faced with huge range of choices and sometimes it is hard for them to find the relevant DBMS. Some Web sites such as DB-Engines (http://db-engines.com/en/) provide monthly a classification of hundreds of DBMS (303 in April 2016) using metrics related to usage and user feedbacks. These criteria are not always sufficient to help companies and users to make a good choice. Therefore, they have to be enhanced by qualitative measurements obtained by testing the activities of DBMS for a set of non-functional requirements. In this perspective, some council such as Transaction Processing Council publish non-functional requirement results of DBMS using their own benchmarks. Another serious producer of test data is the researchers via their scientific papers. Each year they publish a large amount of results of new solutions. To facilitate the exploitation of these test results by small companies and researchers from developing countries, the construction of a test data repository connected to recommender system is an asset for companies/users. In this paper, we first propose a repository for structuring and storing test data. Secondly, a recommender system is built on the top of this repository to advise companies to choose appropriate DBMS based on their requirements. Finally, a proof of concept of our recommender system is given to illustrate our proposal.

Mapping AADL models to a repository of multiple schedulability analysis techniques

To fill the gap between the modeling of real-time systems and the scheduling analysis, we propose a framework that supports seamlessly the two aspects: (1) modeling a system using a methodology, in our case study, the Architecture Analysis and Design Language (AADL), and (2) helping to easily check temporal requirements (schedulability analysis, worst-case response time, sensitivity analysis, etc.). We introduce the usefulness of an intermediate framework called MoSaRT, which supports a rich semantic concerning temporal analysis. We show with a case study how the input model is transformed into a MoSaRT model, and how our framework is able to generate the proper models as inputs to several classic temporal analysis tools.

MetricStore repository: on the leveraging of performance metrics in databases

The database performance is one of the most important quality indicators that companies are looking for to choose their appropriate database management systems. Quantifying this performance is usually performed by the means of mathematical cost models. Due to the importance of these models, for each evolution of the database technology pushes researchers to revisit or to propose cost models in order to integrate new dimensions brought by that evolution. As a consequence, a huge number of cost models exists. To exploit them, we need to find their respective scientific papers. This situation is in contradiction with Era Sharing, because it reduces reuse of these cost models by researchers, students (from third world countries), etc. and even more it penalizes the reproduction of experiments that intensively use these cost models. In this paper, we propose a framework for cost models dedicated to query processing and optimization. We first propose a common repository, called, MetricStore, to store metrics of cost model units. Secondly, thanks to model-driven engineering facilities, the repository offers capabilities aiming at publishing, searching and reusing cost models through a suitable user interface. Tool support is fully available.

Bridging the gap between practical cases and temporal performance analysis: a models repository-based approach

Despite various analysis models and tests proposed by the real-time community to validate the temporal performance of hard real-time systems, several cases derived from industrial practices do not find their corresponding tests in standard schedulability analysis tools. They need to be transformed and adapted in terms of qualitative and quantitative information while remaining conservative. The current state-of-practice of transformation relies solely on designers expertise. As a result, the adaptation/transformation task tends to be time- and effort-intensive. This paper proposes to capitalize adaptation efforts by storing them in a repository, hence designers can be helped to automatically transform and adapt their practical designs to analyzable models while staying conservative. Thanks to model-driven engineering settings the capitalization is illustrated by the implementation of a repository as a decision support and the automatic adaptation relies on model-based transformations. Also, a case study is presented to stress the importance of our contribution.