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Enterprise Architecture Availability Analysis Using Fault Trees and Stakeholder Interviews
KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.ORCID iD: 0000-0003-2017-7914
KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
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2014 (English)In: Enterprise Information Systems, ISSN 1751-7575, E-ISSN 1751-7583, Vol. 8, no 1, 1-25 p.Article in journal (Refereed) Published
Abstract [en]

The availability of enterprise information systems is a key concern for many organisations. This article describes a method for availability analysis based on Fault Tree Analysis and constructs from the ArchiMate enterprise architecture (EA) language. To test the quality of the method, several case-studies within the banking and electrical utility industries were performed. Input data were collected through stakeholder interviews. The results from the case studies were compared with availability of log data to determine the accuracy of the method's predictions. In the five cases where accurate log data were available, the yearly downtime estimates were within eight hours from the actual downtimes. The cost of performing the analysis was low; no case study required more than 20 man-hours of work, making the method ideal for practitioners with an interest in obtaining rapid availability estimates of their enterprise information systems.

Place, publisher, year, edition, pages
2014. Vol. 8, no 1, 1-25 p.
Keyword [en]
availability, enterprise architecture, probabilistic relational models, architecture analysis, fault tree analysis, stakeholder elicitation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-79641DOI: 10.1080/17517575.2011.647092ISI: 000328473200001Scopus ID: 2-s2.0-84890611982OAI: oai:DiVA.org:kth-79641DiVA: diva2:495646
Note

QC 20140122

Available from: 2012-02-09 Created: 2012-02-09 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Analysis of enterprise IT service availability: Enterprise architecture modeling for assessment, prediction, and decision-making
Open this publication in new window or tab >>Analysis of enterprise IT service availability: Enterprise architecture modeling for assessment, prediction, and decision-making
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Abstract [sv]

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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiii, 39 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:032
Keyword
Service Level Agreement, outage costs, Enterprise Architecture, enterprise IT service availability, decision-making, metamodeling, Enterprise Architecture analysis, Bayesian networks, fault trees, Predictive Probabilistic Architecture Modeling Framework, Service Level Agreement, nertidskostnader, Enterprise Architecture, tillgänglighet hos IT-tjänster, beslutsfattande, metamodellering, arkitekturanalys, bayesianska nätverk, felträd, Predictive Probabilistic Architecture Modeling Framework
National Category
Information Systems
Identifiers
urn:nbn:se:kth:diva-101946 (URN)978-91-7501-443-2 (ISBN)
Public defence
2012-10-31, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120912

Available from: 2012-09-12 Created: 2012-09-06 Last updated: 2013-01-28Bibliographically approved
2. Enterprise Architecture for Information System Analysis: Modeling and assessing data accuracy, availability, performance and application usage
Open this publication in new window or tab >>Enterprise Architecture for Information System Analysis: Modeling and assessing data accuracy, availability, performance and application usage
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Decisions concerning IT systems are often made without adequate decision-support. This has led to unnecessary IT costs and failures to realize business benefits. The present thesis presents a framework for analysis of four information systems properties relevant to IT decision-making. The work is founded on enterprise architecture, a model-based IT and business management discipline. Based on the existing ArchiMate framework, a new enterprise architecture framework has been developed and implemented in a software tool. The framework supports modeling and analysis of data accuracy, service performance, service availability and application usage. To analyze data accuracy, data flows are modeled, the service availability analysis uses fault tree analysis, the performance analysis employs queuing networks and the application usage analysis combines the Technology Acceptance Model and Task-Technology Fit model. The accuracy of the framework's estimates was empirically tested. Data accuracy and service performance were evaluated in studies at the same power utility. Service availability was tested in multiple studies at banks and power utilities. Data was collected through interviews with system development or maintenance staff. The application usage model was tested in the maintenance management domain. Here, data was collected by means of a survey answered by 55 respondents from three power utilities, one manufacturing company and one nuclear power plant. The service availability studies provided estimates that were accurate within a few hours of logged yearly downtime. The data accuracy estimate was correct within a percentage point when compared to a sample of data objects. Deviations for four out of five service performance estimates were within 15 % from measured values. The application usage analysis explained a high degree of variation in application usage when applied to the maintenance management domain. During the studies of data accuracy, service performance and service availability, records were kept concerning the required modeling and analysis effort. The estimates were obtained with a total effort of about 20 man-hours per estimate. In summary the framework should be useful for IT decision-makers requiring fairly accurate, but not too expensive, estimates of the four properties.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiii, 41 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:035
Keyword
Enterprise Architecture, Metamodeling, Decision-making, Data Accuracy, Service Availability, Service Performance, Technology Acceptance Model, Task Technology Fit
National Category
Information Systems
Identifiers
urn:nbn:se:kth:diva-101494 (URN)978-91-7501-444-9 (ISBN)
Public defence
2012-09-17, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120912

Available from: 2012-09-12 Created: 2012-08-29 Last updated: 2013-01-28Bibliographically approved

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Franke, UlrikEkstedt, Mathias

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