Darko Huljenic

A Second Replicated Quantitative Analysis of Fault Distributions in Complex Software Systems

To contribute to the body of empirical research on fault distributions during development of complex software systems, a replication of a study of Fenton and Ohlsson is conducted. The hypotheses fr...

Analysis of end-to-end QoS for networked virtual reality services in UMTS

Virtual reality services may be considered a good representative of advanced services in the new-generation network. The focus of this article is to address quality of service support for VR services in the context of the UMTS QoS framework specified by the 3G standardization forum, the Third Generation Partnership Project. We propose a classification of VR services based on delivery requirements (real-time or non-real-time) and degree of interactivity that maps to existing UMTS QoS classes and service attributes. The mapping is based on matching VR service requirements to performance parameters and target values defined for UMTS applications. Test cases involving heterogeneous VR applications are defined, using as a reference a general model for VR service design and delivery. Measurements of network parameters serve to determine the end-to-end QoS requirements of the considered applications, which are in turn mapped to proposed VR service classes.

Mobile agent based software operation and maintenance

The paper deals with a mobile agent based software operation and maintenance. Remote maintenance shell is described as the protected environment allowing software installation, modification and verification on the remote target system, without suspending its regular operation. It is based on the remote operations performed by mobile agents. Multiagent system with collaborative mobile agents, supporting software maintenance, and its architecture are elaborated. Remote maintenance shell implementation in one maintenance session is included.

Intelligent agents for QoS management

This paper addresses the structural and behavioral characteristics of multi-agent system (MAS) for Quality of Service (QoS) management using MESSAGE (Methodology for Engineering Systems of Software Agents) modeling language that extends UML (Unified Modeling Language) by contributing agent knowledge level concepts and diagrams with notation for viewing them. Such a multi-agent system is an environment composed of Intelligent Agents (IAs) that ensure guaranteed QoS offered by multi-service communication networks ac cording to Service Level Agreements (SLAs) among users and service providers. A hybrid layered agent architecture that exploits both goal-orientation and reactiveness is designed. It supports flexible and adaptive behavior as well as collaboration among the intelligent agents. It is shown that the applied multi-agent system for QoS management provides transformation of current communication networks toward a multi-service ubiquitous infrastructure with a unified QoS management architecture.

On the probability distribution of faults in complex software systems

Abstract Context There are several empirical principles related to the distribution of faults in a software system (e.g. the Pareto principle) widely applied in practice and thoroughly studied in the software engineering research providing evidence in their favor. However, the knowledge of the underlying probability distribution of faults, that would enable a systematic approach and refinement of these principles, is still quite limited. Objective In this paper we study the probability distribution of faults detected during verification in four consecutive releases of a large-scale complex software system for the telecommunication exchanges. This is the first such study analyzing closed software system, replicating two previous studies for open source software. Method We take into consideration the Weibull, lognormal, double Pareto, Pareto, and Yule–Simon probability distributions, and investigate how well these distributions fit our empirical fault data using the non-linear regression. Results The results indicate that the double Pareto distribution is the most likely choice for the underlying probability distribution. This is not consistent with the previous studies on open source software. Conclusion The study shows that understanding the probability distribution of faults in complex software systems is more complicated than previously thought. Comparison with previous studies shows that the fault distribution strongly depends on the environment, and only further replications would make it possible to build up a general theory for a given context.

CloudScale: scalability management for cloud systems

This work-in-progress paper introduces the EU FP7 STREP CloudScale. The contribution of this paper is an overall description of CloudScales engineering approach for the design and evolution of scalable cloud applications and services. An Electronic Health Record (EHR) system serves as a motivation scenario. The overall CloudScale method describes how CloudScale will identify and gradually solve scalability problems in this existing applications. CloudScale will also enable the modelling of design alternatives and the analysis of their effect on scalability and cost. Best practices for scalability will further guide the design process. The CloudScale method is supported by three integrated tools and a scalability description modelling language. CloudScale will be validated by two case studies.

Improving software maintenance by using agent-based remote maintenance shell

The paper deals with a method developed for software maintenance called remote maintenance shell. It allows software installation, modification and verification on the remote target system without suspending its regular operation. The method is based on remote operations performed by mobile agents. The role of remote maintenance shell in software maintenance is elaborated, as well as its architecture. A case study on version replacement of an object-oriented application is included.

Communication in machine-to-machine environments

It has been estimated that by the end of 2020 there will be 50 billion connected devices in Machine-to-Machine (M2M) networks. Such projections should encourage us to deal with the corresponding problems in heterogeneous M2M systems. First of all, devices can communicate through different access technologies (e.g. wireline, 2G/3G, WiFi, Bluetooth) and their communication can be classified as direct or indirect, internal or external. In this paper we explain differences between those types of communication and propose a new identification scheme that allows M2M devices to establish communication in every possible way. Secondly, there is a problem of device hardware and software diversity. To over-come this problem, we propose the usage of the Open Service Gateway Initiative (OSGi) framework.

Agents Based Load Balancing with Component Distribution Capability

Distributed processing has become inevitable in many areas today. It can be found in localized systems like multiprocessor computers, in client-server network configurations, in computer clusters or in widely dispersed systems like the Internet. Development of effective techniques for task distribution is considered as one of the biggest issues in parallel and distributed operating environment. Over the past years, a number of load balancing methods has been proposed. This paper describes simulation used for methods comparison. Contrary to the vast of known methods, which are based on client/server technology, a few recent methods are based on mobile agents. This article gives short review of achievements in this area and describes simulation used for agents based load balancing methods comparison. The paper also suggests enhancement in load balancing: mobile agents could include fresh node into the system by installing and starting necessary software components.

Distributed positioning: a network-supported method for satellite positioning performance improvement

Recent studies show that basic satellite positioning is reaching its limits in terms of performance improvements. Further enhancements in positioning performance can be based almost entirely on augmentation and procedures supported by other systems. Considering the complexity of the interrelationship with additional systems, intrinsically different solutions are being developed to solve the positioning performance improvement problem. Here we present a new concept in positioning. Dubbed distributed positioning, it merges basic satellite positioning with advanced and assisted positioning procedures. The resulting complex synergy unavoidably includes the use of additional technologies in mobile communications, wireless Internet, and advanced computer systems. The real advantage from the introduction of distributed positioning lies in its capability to provide a significant improvement in overall positioning performance. Latest navigation status and up-to-date local environment models are much easier to apply on rover positioning, compared with classical assisted-GPS positioning procedures. Distributed positioning presents a completely different approach in positioning performance improvement, opening new prospects in research and development not only in the field of the satellite positioning, but also in telecommunications and computer engineering.