In this dissertation, we develop analytical and computational tools for performance analysis and design of large-scale service systems. The dissertation consists of three main chapters. The first chapter is devoted to devising efficient task assignment policies for large-scale service system models from a rare event analysis standpoint. Specifically, we study the steady-state behavior of multi-server queues with general job size distributions under size-interval task assignment (SITA) policies. Assuming Poisson arrivals and the existence of the alpha-th moment of the job size distribution for some alpha> 1, we show that if the job arrival rate and the number of servers increase to infinity with the traffic intensity held fixed, a SITA policy parameterized by alpha minimizes in a large deviation sense the steady-state probability that the total number of jobs in the system is greater than or equal to the number of servers. The optimal large deviation decay rate can be arbitrarily close to the one for the corresponding probability in an infinite-server queue, which only depends on the system traffic intensity but not on any higher moments of the job size distribution. This supports in a many-server asymptotic framework the common wisdom that separating large jobs from small jobs protects system performance against job size variability. In the second chapter, we study constraint satisfaction problems for a Markovian parallel-server queueing model with impatient customers, motivated by large telephone call centers. To minimize the staffing level subject to different service-level constraints, we propose refined square-root staffing (SRS) rules, which preserve the insightfulness and computational scalability of the celebrated SRS principle and yet achieve a stronger form of optimality. In particular, using asymptotic series expansion techniques, we first develop refinements to a set of asymptotic performance approximations recently used in analyzing large call centers, namely, the Quality and Efficiency Driven (QED) diffusion approximations. We then use the improved performance approximations to explicitly characterize the error of conventional SRS and further obtain the refined SRS rules. Finally, we demonstrate how the explicit form of the staffing refinements enables an analytical assessment of the accuracy of conventional SRS and its underlying QED approximation. In the third chapter, we study a fluid model for many-server Markovian queues in changing environments, which can be used to model large-scale service systems with customer abandonments and time-varying arrivals. We obtain the stationary distribution of the fluid model, which refines and is shown to converge, as the environment changing rate vanishes in a proper way, to a simple discrete bimodal approximation. We also prove that the fluid model arises as a law of large number limit in a many-server asymptotic regime.

Context. Software re-engineering has been identified as a business critical activity to improve legacy systems in industries. It is the process of understanding existing software and improving it, for modified or improved functionality, better maintainability, configurability, reusability, or other quality goals. However, there is little knowledge to integrate software quality attributes into the re-engineering process. It is essential to resolve quality problems through applying software re-engineering processes. Objectives. In this study we perform an in-depth investigation to identify and resolve quality problems by applying software re-engineering processes. At the end, we created a quality driven re-engineering framework. Methods. At first, we conducted a literature review to get knowledge for building the quality driven re-engineering framework. After that, we performed a case study in Ericsson Company to validate the processes of the framework. At last, we carried out an experiment to prove that the identified quality problems has been resolved. Results. We compared three existing re-engineering frameworks and identified their weaknesses. In order to fix the weaknesses, we created a quality driven re-engineering framework. This framework is used to improve software quality through identifying and resolving root cause problems in legacy systems. Moreover, we validated the framework for one type of legacy system by successfully applying the framework in a real case in Ericsson Company. And also, we proved that the efficiency of a legacy system is improved after executing an experiment in Ericsson Company. Conclusions. We conclude that the quality driven re-engineering framework is applicable, and it can improve efficiency of a legacy system. Moreover, we conclude that there is a need for further empirical validation of the framework in full scale industrial trials.

Architecting e-business applications is a complex design activity. This is mainly due to the numerous architectural decisions to be made, including the selection of alternative technologies, software components, design strategies, patterns, standards, protocols, platforms, etc. Further complexities arise due to the fact that these alternatives often vary considerably in their support for different quality attributes. Moreover, there are often different groups of stakeholders involved, with each having their own quality goals and criteria. Furthermore, different architectural decisions often include interdependent alternatives, where the selection of one alternative for one particular decision impacts the selections to be made for alternatives from other different decisions. There have been several research efforts aiming at providing sufficient mechanisms and tools for facilitating the architectural evaluation and design process. These approaches, however, address architectural decisions in isolation, where they focus on evaluating a limited set of alternatives belonging to one architectural decision. This has been the primary motivation behind the development of the Architectural DEcision-Making Support (ADEMS) framework, which basically aims at supporting stakeholders and architects during the architectural decision-making process by helping them determining a suitable combination of architectural alternatives. ADEMS framework is an iterative process that leverages rigorous quantitative decision-making techniques available in the literature of Management Science, particularly Multiple Attribute Decision-Making (MADM) methods and Integer Programming (IP). Furthermore, due to the number of architectural decisions involved as well as the variety of available alternatives, the architecture design space is expected to be huge. For this purpose, a query language has been developed, known as the Architecture Query Language (AQL), to aid architects in exploring and analyzing the design space in further depth, and also in examining different ???what-if??? architectural scenarios. In addition, in order to support leveraging ADEMS framework, a support tool has been implemented for carrying out the sophisticated set of mathematical computations and comparisons of the large number of architectural combinations, which might otherwise be hard to conduct using manual techniques. The primary contribution of the tool is in its help to identify, evaluate, and rank all potential combinations of alternatives based on their satisfaction to quality preferences provided by the different stakeholders. Finally, to assess the feasibility of ADEMS, three different case studies have been conducted relating to the architectural evaluation of different e-business and enterprise applications. Results obtained for the three case studies were quite positive as they showed an acceptable accuracy level for the decisions recommended by ADEMS, and at a reasonable time and effort costs for the different system stakeholders.

Titel: Anställdas reaktioner vid kvalitetsdrivet utvecklingsarbete, fokus på motståndens art, konsekvenser och hantering Nivå: C-uppsats i företagsekonomi Författare: Marie Olsson, Emelie Mårtensson Handledare: Tomas Källquist, Stig Sörling Datum: 2013-06-11 Syfte: Studiens syfte är att belysa motstånd från anställda mot kvalitetsdrivet utvecklingsarbete och belysa olika sätt för ledningen att bemöta dessa motstånd. Metod: Litteratur och tidigare forskning om kvalitetsarbete och motstånd från anställda studerades. Även ledare- och ledningens roll i arbetet mot motstånd studerades. Därefter undersöktes hur respondenterna i fallföretagen arbetar med kvalitet och vilka erfarenheter de har av motstånd. Reflektion: Det visade sig att tidigare forskning och den insamlade empirin hade flera likheter, bland annat huvudteman som kommunikation, struktur och mänskligt beteende. Förslag till fortsatt forskning: Denna studie belyser endast motstånd, som är en av många olika reaktioner. Detta bör tas fasta på i andra studier, och därför belysa vilka reaktioner som kan uppstå vid en kvalitetsdriven förändring. För fortsatt forskning vore det också intressant att överblicka hur motstånden kan te sig mot förnyelsearbete rent generellt, och bortse från kvalitetsfokus. Är det samma faktorer som påverkar som vid ett kvalitetsdrivet utvecklingsarbete? Förutom att belysa motstånd finns också möjligheten att rikta sig mot de koncept som finns, och belysa hur de används idag jämfört med tidigare. Studien har även uppmärksammat att TQM inte används i samma utsträckning idag, och att företag istället väljer att inspireras av dem. Vad kan denna utveckling bero på, varför har företag som implementerat konceptet valt att frångå detta? Uppsatsens bidrag: I dagsläget finns mer teoretiskt material än empiriska synvinklar på motstånd från anställda i ett kvalitetsdrivet utvecklingsarbete. Det finns en mängd litteratur och tidigare forskning kring ämnet men färre fallstudier, hur problemen verkligen förefaller i praktiken, varför denna studie behövs. Nyckelord: Kvalitetsdrivet utvecklingsarbete, Motstånd, Kvalitetsarbete, Anställda, Ledare- och ledningens roll. / Title: Employee reactions to quality-driven development, focus on resistance, its nature, consequences and managing. Level: Final assignment for Bachelor's Degree in Business Administration Author: Marie Olsson, Emelie Mårtensson Supervisor: Tomas Källquist, Stig Sörling Date: 2013-06-11 Aim: The purpose of this study is to illustrate resistance from employees towards quality-driven development and ways for management to respond to these resistors. Method: The literature and previous research of quality work and resistance from employees was studied. Leaders and leadershiprole in the resistance was also studied. Next, the study examined how respondents in the case company committed to quality and their experiences of resistance. Reflection: It turned out that previous research and the collected empirical data had many similarities, including keytopics such as communication, structure and human behavior. Suggestions for future research: This study has only studied resistors, and therefore would a study that illustrates the reactions that occur in a quality driven change be interesting. For future research it would also be interesting to conduct a study overviews how resistance may seem to renewal in general, apart from the quality focus. Is it the same factors that affects as in a quality-driven development? In addition to illustrate resistance is also the possibility of targeting the concepts that are available today, and how they are used. The study has noted that TQM is not used to the same extent today, and that companies instead choose to be inspired by them. What might this evolution depend on, why have companies that implemented the concept chosen to deviate from this? Contribution of the thesis: In the current situation there is more theoretical than empirical perspectives on resistance from employees in quality-driven development. There are a variety of literature and previous research about the subject but fewer case studies where you can really see how the problems seem in practice, wich is why that this study is necessary. Keywords: Quality-driven development, Resistance, Quality work, Employees, Leaders and leadershiprole.

In vielen Bereichen des täglichen Lebens, angefangen vom Online-Banking bis hin zur Steuerung im Flugzeug, kommt Software mit laufzeitkritischen nicht-funktionalen Eigenschaften (NFE) zum Einsatz. Die Erfüllung der NFE spielt in diesen Anwendungen eine zentrale Rolle. Um dies zu erreichen, ist eine systematische und zielorientierte Behandlung dieser Anforderungen während der Entwicklung zwingend erforderlich. NFE zeichnen sich im Gegensatz zu funktionalen Eigenschaften durch besondere Merkmale aus, die ein adaptives Vorgehen zur Definition des Entwicklungsprozesses erzwingen. In der Arbeit wird eine Methodik zur kontextbasierten Anpassung von Vorgehensmodellen an laufzeitkritische NFE auf der Basis von Prozessmustern sowie das PROKRIS-Framework als unterstützende Umgebung vorgestellt.

Architecting e-business applications is a complex design activity. This is mainly due to the numerous architectural decisions to be made, including the selection of alternative technologies, software components, design strategies, patterns, standards, protocols, platforms, etc. Further complexities arise due to the fact that these alternatives often vary considerably in their support for different quality attributes. Moreover, there are often different groups of stakeholders involved, with each having their own quality goals and criteria. Furthermore, different architectural decisions often include interdependent alternatives, where the selection of one alternative for one particular decision impacts the selections to be made for alternatives from other different decisions. There have been several research efforts aiming at providing sufficient mechanisms and tools for facilitating the architectural evaluation and design process. These approaches, however, address architectural decisions in isolation, where they focus on evaluating a limited set of alternatives belonging to one architectural decision. This has been the primary motivation behind the development of the Architectural DEcision-Making Support (ADEMS) framework, which basically aims at supporting stakeholders and architects during the architectural decision-making process by helping them determining a suitable combination of architectural alternatives. ADEMS framework is an iterative process that leverages rigorous quantitative decision-making techniques available in the literature of Management Science, particularly Multiple Attribute Decision-Making (MADM) methods and Integer Programming (IP). Furthermore, due to the number of architectural decisions involved as well as the variety of available alternatives, the architecture design space is expected to be huge. For this purpose, a query language has been developed, known as the Architecture Query Language (AQL), to aid architects in exploring and analyzing the design space in further depth, and also in examining different ???what-if??? architectural scenarios. In addition, in order to support leveraging ADEMS framework, a support tool has been implemented for carrying out the sophisticated set of mathematical computations and comparisons of the large number of architectural combinations, which might otherwise be hard to conduct using manual techniques. The primary contribution of the tool is in its help to identify, evaluate, and rank all potential combinations of alternatives based on their satisfaction to quality preferences provided by the different stakeholders. Finally, to assess the feasibility of ADEMS, three different case studies have been conducted relating to the architectural evaluation of different e-business and enterprise applications. Results obtained for the three case studies were quite positive as they showed an acceptable accuracy level for the decisions recommended by ADEMS, and at a reasonable time and effort costs for the different system stakeholders.

In vielen Bereichen des täglichen Lebens, angefangen vom Online-Banking bis hin zur Steuerung im Flugzeug, kommt Software mit laufzeitkritischen nicht-funktionalen Eigenschaften (NFE) zum Einsatz. Die Erfüllung der NFE spielt in diesen Anwendungen eine zentrale Rolle. Um dies zu erreichen, ist eine systematische und zielorientierte Behandlung dieser Anforderungen während der Entwicklung zwingend erforderlich. NFE zeichnen sich im Gegensatz zu funktionalen Eigenschaften durch besondere Merkmale aus, die ein adaptives Vorgehen zur Definition des Entwicklungsprozesses erzwingen. In der Arbeit wird eine Methodik zur kontextbasierten Anpassung von Vorgehensmodellen an laufzeitkritische NFE auf der Basis von Prozessmustern sowie das PROKRIS-Framework als unterstützende Umgebung vorgestellt.

L'un des défis actuels de la chimie alimentaire est de développer des produits avec une qualité sanitaire et sensorielle optimale. Ceci est particulièrement important dans les produits traités thermiquement, tels que les produits céréaliers. Lors de la cuisson et à partir des ingrédients, un nombre considérable de composés peuvent se former. Certains suscitent une préoccupation sanitaire émergente, lorsque d'autres jouent un rôle sensoriel indéniable. Comprendre la réactivité des constituants devient alors un levier puissant pour développer des voies d'amélioration des aliments. Ce travail porte sur les effets des ingrédients et conditions de cuisson dans la génération de furane, composé possiblement cancérigène, et furfural, composé odorant contribuant à l'arôme caractéristique de la génoise. Afin de maîtriser la réactivité et ainsi optimiser la qualité des produits, une approche globale a été adoptée, incluant l'étude des composés volatils, des propriétés physicochimiques et sensorielles et l'appréciation hédonique des consommateurs. Ce travail propose une méthodologie et ouvre des pistes intéressantes pour développer des stratégies efficaces de maîtrise de la qualité globale des produits transformés. / A current challenge for food chemists consists in developing safe yet appealing food. This is particularly difficult in thermally-treated foods, like baked products, since a great number of compounds may be produced during heating. While some of these are of health concern, others contribute to other key aspects of quality, such as aroma or color, revealing the need of considering reactivity into food quality design. This work deals with the effects of formulation and baking conditions on the generation of furan, a heatinduced contaminant, and furfural, contributing typical aroma to sponge cake. Moreover, a holistic approach was adopted, covering volatile generation, physical properties, sensory evaluation and consumer tests, both for further understanding reactivity and optimizing product quality. This work is certainly an important step towards the development of novel strategies for qualitydriven design of heat-treated food.