Contemporary enterprises depend to great extent on software systems. During the past decades the number of systems has been constantly increasing and these systems have become more integrated with one another. This has lead to a growing complexity in managing software systems and their environment. At the same time business environments today need to progress and change rapidly to keep up with evolving markets. As the business processes change, the systems need to be modified in order to continue supporting the processes. The complexity increase and growing demand for rapid change makes the management of enterprise systems a very important issue. In order to achieve effective and efficient management, it is essential to be able to analyze the system modifiability (i.e. estimate the future change cost). This is addressed in the thesis by employing architectural models. The contribution of this thesis is a method for software system modifiability analysis using enterprise architecture models. The contribution includes an enterprise architecture analysis formalism, a modifiability metamodel (i.e. a modeling language), and a method for creating metamodels. The proposed approach allows IT-decision makers to model and analyze change projects. By doing so, high-quality decision support regarding change project costs is received. This thesis is a composite thesis consisting of five papers and an introduction. Paper A evaluatesa number of analysis formalisms and proposes extended influence diagrams to be employed for enterprise architecture analysis. Paper B presents the first version of the modifiability metamodel. InPaper C, a method for creating enterprise architecture metamodels is proposed. This method aims to be general, i.e. can be employed for other IT-related quality analyses such as interoperability, security, and availability. The paper does however use modifiability as a running case. The second version of the modifiability metamodel for change project cost estimation is fully described in Paper D. Finally, Paper E validates the proposed method and metamodel by surveying 110 experts and studying 21 change projects at four large Nordic companies. The validation indicates that the method and metamodel are useful, contain the right set of elements and provide good estimation capabilities. / QC20100716

This project presents a case study of modifiability analysis on the Information Systems which are central to the core business processes of Royal Institution of Technology in Stockholm, Sweden by creating, updating and using models. The case study was limited to modifiability regarding only specified Information Systems. The method selected was Enterprise Architecture together with Enterprise Architecture Analysis research results and tools from the Industrial Information and Control Systems department of the same University. Jointly used with the ArchiMate modelling language, to create the models and perform the analysis. The results demonstrated to be very varied in regards to system models and modifiability. The Alumni Commu-nity system seemed to have very high modifiability whereas the Ladok på Webben system seemed to have the low modifiability, and other systems ranging differently or in between. The case study results found three slightly more critical systems of all the systems analysed: Ladok på Webben, Nya Antagningen & La-dok Nouveau. The first two showed to have either very low or low modifiability while being highly coupled to the other systems. Therefore any modification to these two systems would most likely cause effects that would require change in interconnected systems. Whereas Ladok Nouveau, while having average modifia-bility, has a critical position to process activities, is nearly isolated from all other systems, making them indi-rectly dependent on the system through the interconnected LADOK database. The study showed that the systems developed at KTH are comparable with systems developed by commercial enterprises in terms of modifiability. The study also provided insight into an Enterprise Architecture where the systems have dif-ferent development origins and how this could affect modifiability and analysis.

Information technology has become increasingly important to individuals and organizations alike. Not only does IT allow us to do what we always did faster and more effectively, but it also allows us to do new things, organize ourselves differently, and work in ways previously unimaginable. However, these advantages come at a cost: as we become increasingly dependent upon IT services, we also demand that they are continuously and uninterruptedly available for use. Despite advances in reliability engineering, the complexity of today's increasingly integrated systems offers a non-trivial challenge in this respect. How can high availability of enterprise IT services be maintained in the face of constant additions and upgrades, decade-long life-cycles, dependencies upon third-parties and the ever-present business-imposed requirement of flexible and agile IT services? The contribution of this thesis includes (i) an enterprise architecture framework that offers a unique and action-guiding way to analyze service availability, (ii) identification of causal factors that affect the availability of enterprise IT services, (iii) a study of the use of fault trees for enterprise architecture availability analysis, and (iv) principles for how to think about availability management. This thesis is a composite thesis of five papers. Paper 1 offers a framework for thinking about enterprise IT service availability management, highlighting the importance of variance of outage costs. Paper 2 shows how enterprise architecture (EA) frameworks for dependency analysis can be extended with Fault Tree Analysis (FTA) and Bayesian networks (BN) techniques. FTA and BN are proven formal methods for reliability and availability modeling. Paper 3 describes a Bayesian prediction model for systems availability, based on expert elicitation from 50 experts. Paper 4 combines FTA and constructs from the ArchiMate EA language into a method for availability analysis on the enterprise level. The method is validated by five case studies, where annual downtime estimates were always within eight hours from the actual values. Paper 5 extends the Bayesian prediction model from paper 3 and the modeling method from paper 4 into a full-blown enterprise architecture framework, expressed in a probabilistic version of the Object Constraint Language. The resulting modeling framework is tested in nine case studies of enterprise information systems. / Informationsteknik blir allt viktigare för både enskilda individer och för organisationer. IT låter oss inte bara arbeta snabbare och effektivare med det vi redan gör, utan låter oss också göra helt nya saker, organisera oss annorlunda och arbeta på nya sätt. Tyvärr har dessa fördelar ett pris: i takt med att vi blir alltmer beroende av IT-tjänster ökar också våra krav på att de är ständigt tillgängliga för oss, utan avbrott. Trots att tillförlitlighetstekniken går framåt utgör dagens alltmer sammankopplade system en svår utmaning i detta avseende. Hur kan man säkerställa hög tillgänglighet hos IT-tjänster som ständigt byggs ut och uppgraderas, som har livscykler på tiotals år, som är beroende av tredjepartsleverantörer och som dessutom måste leva upp till verksamhetskrav på att vara flexibla och agila? Den här avhandlingen innehåller (i) ett arkitekturramverk som på ett unikt sätt kan analysera IT-tjänsters tillgänglighet och ta fram rekommenderade åtgärder, (ii) ett antal identifierade kausalfaktorer som påverkar IT-tjänsters tillgänglighet, (iii) en studie av hur felträd kan användas för arkitekturanalys av tillgänglighet samt (iv) en uppsättning principer för beslutsfattande kring tillgänglighet. Avhandlingen är en sammanläggningsavhandling med fem artiklar. Artikel 1 innehåller ett konceptuellt ramverk för beslutsfattande kring IT-tjänsters tillgänglighet som understryker vikten av variansen hos nertidskostnaderna. Artikel 2 visar hur ramverk för organisationsövergripande arkitektur (s.k. enterprise architecture -- EA) kan utvidgas med felträdsanalys (FTA) och bayesianska nätverk (BN) för analys av beroenden mellan komponenter. FTA och BN är bägge etablerade metoder för tillförlitlighets- och tillgänglighetsmodellering. Artikel 3 beskriver en bayesiansk prediktionsmodell för systemtillgänglighet, baserad på utlåtanden från 50 experter. Artikel 4 kombinerar FTA med modelleringselement från EA-ramverket ArchiMate till en metod för tillgänglighetsanalys på verksamhetsnivå. Metoden har validerats i fem fallstudier, där de estimerade årliga nertiderna alltid låg inom åtta timmar från de faktiska värdena. Artikel 5 utvidgar den bayesianska prediktionsmodellen från artikel 3 och modelleringsmetoden från artikel 4 till ett fullständigt EA-ramverk som uttrycks i en probabilistisk version av Object Constraint Language (OCL). Det resulterande modelleringsramverket har testats i nio fallstudier på verksamhetsstödjande IT-system. / <p>QC 20120912</p>