Structured Performance Analysis for Component Based Systems

International audienceThe Component Based System (CBS) paradigm is now largely used to design software systems. In addition, performance and behavioural analysis remains a required step for the design and the construction of efficient systems. This is especially the case of CBS, which involve interconnected components running concurrent processes. % This paper proposes a compositional method for modeling and structured performance analysis of CBS. Modeling is based on Stochastic Well-formed Nets (SWN), a high level model of Stochastic Petri nets, widely used for dependability analysis of concurrent systems. Starting from the definition of the system given in a suitable Architecture Description Language, and from the definition of the elementary components, we build an SWN of the global system together with a set of SWNs modeling the components of the CBS and their connections. From these models, we derive performances of the system thanks to a structured analysis induced by the structure of the CBS. We describe the application of our method through an example designed in the framework of the CORBA Component Model

The GreatSPN tool: recent enhancements

GreatSPN is a tool that supports the design and the qualitative and quantitative analysis of Generalized Stochastic Petri Nets (GSPN) and of Stochastic Well-Formed Nets (SWN). The very first version of GreatSPN saw the light in the late eighties of last century: since then two main releases where developed and widely distributed to the research community: GreatSPN1.7 [13], and GreatSPN2.0 [8]. This paper reviews the main functionalities of GreatSPN2.0 and presents some recently added features that significantly enhance the efficacy of the tool

Extended Fault Trees Analysis supported by Stochastic Petri Nets

This work presents several extensions to the Fault Tree [90] formalism used to build models oriented to the Dependability [103] analysis of systems. In this way, we increment the modelling capacity of Fault Trees which turn from simple combinatorial models to an high level language to represent more complicated aspects of the behaviour and of the failure mode of systems. Together with the extensions to the Fault Tree formalism, this work proposes solution methods for extended Fault Trees in order to cope with the new modelling facilities. These methods are mainly based on the use of Stochastic Petri Nets. Some of the formalisms described in this work are already present in the literature; for them we propose alternative solution methods with respect to the existing ones. Other formalisms are instead part of the original contribution of this work

A UML Profile for the Design, Quality Assessment and Deployment of Data-intensive Applications

Big Data or Data-Intensive applications (DIAs) seek to mine, manipulate, extract or otherwise exploit the potential intelligence hidden behind Big Data. However, several practitioner surveys remark that DIAs potential is still untapped because of very difficult and costly design, quality assessment and continuous refinement. To address the above shortcoming, we propose the use of a UML domain-specific modeling language or profile specifically tailored to support the design, assessment and continuous deployment of DIAs. This article illustrates our DIA-specific profile and outlines its usage in the context of DIA performance engineering and deployment. For DIA performance engineering, we rely on the Apache Hadoop technology, while for DIA deployment, we leverage the TOSCA language. We conclude that the proposed profile offers a powerful language for data-intensive software and systems modeling, quality evaluation and automated deployment of DIAs on private or public clouds

Third Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, August 29-31, 2001

This booklet contains the proceedings of the Third Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, August 29-31, 2001. The workshop is organised by the CPN group at Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop01

Improving resilience to cyber-attacks by analysing system output impacts and costs

Cyber-attacks cost businesses millions of dollars every year, a key component of which is the cost of business disruption from system downtime. As cyber-attacks cannot all be prevented, there is a need to consider the cyber resilience of systems, i.e. the ability to withstand cyber-attacks and recover from them. Previous works discussing system cyber resilience typically either offer generic high-level guidance on best practices, provide limited attack modelling, or apply to systems with special characteristics. There is a lack of an approach to system cyber resilience evaluation that is generally applicable yet provides a detailed consideration for the system-level impacts of cyber-attacks and defences. We propose a methodology for evaluating the effectiveness of actions intended to improve resilience to cyber-attacks, considering their impacts on system output performance, and monetary costs. It is intended for analysing attacks that can disrupt the system function, and involves modelling attack progression, system output production, response to attacks, and costs from cyber-attacks and defensive actions. Studies of three use cases demonstrate the implementation and usefulness of our methodology. First, in our redundancy planning study, we considered the effect of redundancy additions on mitigating the impacts of cyber-attacks on system output performance. We found that redundancy with diversity can be effective in increasing resilience, although the reduction in attack-related costs must be balanced against added maintenance costs. Second, our work on attack countermeasure selection shows that by considering system output impacts across the duration of an attack, one can find more cost-effective attack responses than without such considerations. Third, we propose an approach to mission viability analysis for multi-UAV deployments facing cyber-attacks, which can aid resource planning and determining if the mission can conclude successfully despite an attack. We provide different implementations of our model components, based on use case requirements.Open Acces

Experimental studies of intra- and intermolecular chemical structure

The purpose of this study was two fold. The determination of hydrogen atom positions by X-ray diffraction methods is widely underused. With advances in instrument and computing technology, the use of X-ray diffraction experiments to accurately image the electron density associated with a hydrogen bond has become feasible. Secondly, general crystallographic computing programs analyze diffraction data by employing a spherical atom model. However, no such atom can be defined solely by a sphere when bound in a molecule. The use of spherical harmonics to model diffraction data enables a more complete description of the electron density in a molecular system. The use of these types of programs has allowed a detailed analysis of a variety of both hydrogen bonded and non-hydrogen bonded system. This dissertation details the experimental information for charge density and hydrogen bonding studies. The experimental results are analyzed in depth to yield a more complete understanding of a variety of bonding motifs. In some cases, the DFT calculations were performed to augment the experimental results. A series of other experimental components are added to yield a more complete structural model of each molecular system. Chapter one presents a solid background to X-ray diffraction and the solid state. The information presented in the chapter describes the development of X-ray diffraction, various techniques and the experimental methods available to model diffraction data. Chapter one also develops the basic concepts for understanding the crystalline sold state. Chapter two gives a detailed introduction to hydrogen bonding and the use of diffraction technique to model the electron and nuclear density as well as define the distribution of these densities in a three-center four-electron bond. The first molecule analyzed is urotropine-N-oxide∙formic acid, which consists of a short, strong, symmetric hydrogen bond. Variable temperature X-ray diffraction studies were used to model the total electron density in the hydrogen bond through the use of Fourier difference maps, while neutron diffraction experiments were used to confirm the proton position in the hydrogen bond. The second system analyzed was para-iodobenzoic acid. Variable temperature X-ray diffraction experiments revealed a split-site population of the electron density associated with the proton position, as is evident by the use of difference Fourier maps. Chapter three contains the detailed charge density analysis of a material containing a short, strong, asymmetric hydrogen bond, namely cobaltocenium 3,5 bis(trifluoromethyl)phenoxide 3,5-bis(trifluoromethyl)phenol. High resolution X-ray diffraction data were collected to give insight into the chemical bonding both in the hydrogen bond as well as in the organometallic segment. Chapter four focuses on the charge density studies on a novel heterocyclic alkene, 1,2,3,4,5,6,7,8-octahydro-2a,4a,6a,8a-tetraaza-cyclopenta[fg]acenaphthylene. Accurate determination of the electron density in this system demonstrates a delocalization of the electron density on the p orbitals on nitrogen over the π system. Chapter five is a detailed experimental section for all material covered in this body of work

An Introduction to Database Systems

This textbook introduces the basic concepts of database systems. These concepts are presented through numerous examples in modeling and design. The material in this book is geared to an introductory course in database systems offered at the junior or senior level of Computer Science. It could also be used in a first year graduate course in database systems, focusing on a selection of the advanced topics in the latter chapters