The practice of composing web services has received an increasing interest with the emerging application development architecture called Service Oriented Architecture (SOA). A web service composition can be done either manually or (semi-) automatically. Doing composition (semi-) automatically minimizes runtime problems that arise due to dynamic nature of runtime environments. However, the implementation of (semi-) automatic composition demands for the automation of a process model or a composition plan generation process. In addition, creating a composite service or applications from component services, that are developed and meant to work independently, causes unavoidable dependencies among the services involved. Consequently, in a composite service development, understanding, analyzing and tracking of such dependencies becomes important. This thesis views the process model generation sub-task of a service composition as a service dependency identifification and analysis problem. In this thesis, we propose a dependency based automatic process model generation methods. For this purpose, the following issues are explored. First, a top layer architecture with a composition engine is developed. The architecture gives a complete picture of dependency based automatic service composition. Second, the process model generation sub-task is formulated as a service dependency identification and analysis problem. Third, a two-stepped method for automatic process model generation, given a set of candidate web service descriptions, is proposed. The first step of the proposed approach deals with the identifification of potential direct and indirect dependencies between abstract services. The direct dependency extraction is done by assuming a semantic I/O matching of service parameters. The extraction of indirect dependency from direct dependency is done using a recursive algorithm derived from the transitive closure property. Alternatively the Warshall algorithm is used. The second step of the proposed approach deals with analysis of dependency information and generation of process model (PM) automatically. To execute this step, we propose two approaches: matrix based and graph based approaches. The matrix based approach utilizes both direct and indirect dependencies. This approach represents dependencies using matrix and takes advantages of a sorting algorithm. The matrix representation facilitates a simplistic mathematical dependency analysis for generating important indicators during automatic process model creation. The process model is generated using a sorting algorithm that uses the analysis result obtained from the dependency matrix as sorting criterion. The graph based approach uses only direct dependency among candidate services. As its name indicates, in this approach the extracted I/O dependencies are represented using a directed graph. A modifified topological sorting algorithm is used for generating a process model that shows the execution order of candidate services. Both of the proposed approaches (matrix and graph based approaches) recognize the existence of cyclic dependencies and provide ways of dealing with them. The resulting process model or composition plan from both approaches has a sequential, concurrent and loop control flows. Finally, the performance of the proposed approaches is studied theoretically as well as experimentally. For the experimental validation and evaluation purpose, the approaches are implemented in a prototype that facilitates the validation and evaluation of the approaches at a larger scale. An extensive experimental performance evaluation is done fifirst on each proposed approach. The two approaches are then compared and their pros and cons under difffferent scenarios are assessed.

The practice of composing web services has received an increasing interest with the emerging application development architecture called Service Oriented Architecture (SOA). A web service composition can be done either manually or (semi-) automatically. Doing composition (semi-) automatically minimizes runtime problems that arise due to dynamic nature of runtime environments. However, the implementation of (semi-) automatic composition demands for the automation of a process model or a composition plan generation process. In addition, creating a composite service or applications from component services, that are developed and meant to work independently, causes unavoidable dependencies among the services involved. Consequently, in a composite service development, understanding, analyzing and tracking of such dependencies becomes important. This thesis views the process model generation sub-task of a service composition as a service dependency identifification and analysis problem. In this thesis, we propose a dependency based automatic process model generation methods. For this purpose, the following issues are explored. First, a top layer architecture with a composition engine is developed. The architecture gives a complete picture of dependency based automatic service composition. Second, the process model generation sub-task is formulated as a service dependency identification and analysis problem. Third, a two-stepped method for automatic process model generation, given a set of candidate web service descriptions, is proposed. The first step of the proposed approach deals with the identifification of potential direct and indirect dependencies between abstract services. The direct dependency extraction is done by assuming a semantic I/O matching of service parameters. The extraction of indirect dependency from direct dependency is done using a recursive algorithm derived from the transitive closure property. Alternatively the Warshall algorithm is used. The second step of the proposed approach deals with analysis of dependency information and generation of process model (PM) automatically. To execute this step, we propose two approaches: matrix based and graph based approaches. The matrix based approach utilizes both direct and indirect dependencies. This approach represents dependencies using matrix and takes advantages of a sorting algorithm. The matrix representation facilitates a simplistic mathematical dependency analysis for generating important indicators during automatic process model creation. The process model is generated using a sorting algorithm that uses the analysis result obtained from the dependency matrix as sorting criterion. The graph based approach uses only direct dependency among candidate services. As its name indicates, in this approach the extracted I/O dependencies are represented using a directed graph. A modifified topological sorting algorithm is used for generating a process model that shows the execution order of candidate services. Both of the proposed approaches (matrix and graph based approaches) recognize the existence of cyclic dependencies and provide ways of dealing with them. The resulting process model or composition plan from both approaches has a sequential, concurrent and loop control flows. Finally, the performance of the proposed approaches is studied theoretically as well as experimentally. For the experimental validation and evaluation purpose, the approaches are implemented in a prototype that facilitates the validation and evaluation of the approaches at a larger scale. An extensive experimental performance evaluation is done fifirst on each proposed approach. The two approaches are then compared and their pros and cons under difffferent scenarios are assessed.

Die steigende Nachfrage an immer komplexeren Systemen in verschiedensten wirtschaftlichen Bereichen, erfordert Strategien, die Wartbarkeit und Wiederverwendbarkeit unterstützen. An diesem Punkt setzen service-orientierte Architekturen (SOAn) an. Dieses Paradigma fordert die Aufspaltung von Funktionalität in Services, die komponiert werden können, um eine gewünschte, komplexe Funktionalität zu erreichen. Besonders in sicherheitskritischen Bereichen, kann eine fehlerbehaftete Komposition jedoch zu hohen finanziellen Einbußen oder sogar zu lebensbedrohlichen Situationen führen. Um die Korrektheit sicherzustellen, müssen Kompositionsmethoden im Vorfeld definierte Eigenschaften garantieren und die, durch die unabhängige Entwicklung auftretenden, Interface-Inkompatibilitäten behandeln. Existierende Ansätze zur automatisierten Service-Komposition durch Controller-Synthese beinhalten jedoch keine formale Datenbehandlung und können daher nicht mit datenabhängigem Verhalten umgehen. In der vorliegenden Arbeit, löse ich dieses Problem durch die Bereitstellung eines Ansatzes zur automatisierten Synthese datenabhängiger, korrekter Service-Controller. Dabei wird ein Controller direkt aus den spezifizierten Anforderungen und dem Verhalten der Services erzeugt. Basierend auf den Annahmen, dass die Anforderungen in RCTL, einer Untermenge der Computational Tree Logic (CTL), spezifiziert und die Services als Algebraische Petrinetze (APNe) gegeben sind, vereinigt mein neuartiger Ansatz die beiden Formalismen und unterstützt eine zuverlässige Extraktion des Controller-Verhaltens. Durch die Nutzung der APNe, erlaubt der Ansatz eine formale Datenbehandlung und somit eine Betrachtung datenabhängigen Verhaltens. Die Anwendbarkeit meines Ansatzes habe ich an drei Fallstudien aus dem medizinischen Bereich gezeigt, wo Geräte sicher miteinander kommunizieren müssen. / The continuously increasing demand for more complex systems in various economical domains requires a strategy that supports maintainability and reusability. This is addressed by the service-oriented architecture (SOA)}-paradigm that encourages the encapsulation of functionality into services. To achieve a specific functionality, services can be composed. Especially in safety-critical systems, an incorrect composition of various components can lead to high financial losses or even life threatening situations. To ensure the correctness, composition methods must particularly be able to guarantee pre-specified requirements and to overcome interface incompatibilities, which result from the independent development of the single services. However, current approaches for automated service composition via controller synthesis do not support a formal data-treatment and do not cope with data-dependent behavior. In this thesis, we overcome this problem by providing an approach for the automated synthesis of data-dependent service controllers that are correct-by-construction. The core idea is to synthesize such a controller directly from given requirements and the behavior of the services. Based on the assumptions that the requirements are specified using a subset of Computational Tree Logic (CTL), called RCTL, and that the services are given as algebraic Petri Nets (APNs), our novel synthesis process unifies the two formalisms and enables a reliable extraction of the controller behavior. Especially due to the use of APNs, our approach supports a formal data-treatment and enables a consideration of data-dependent behavior. With our synthesis process, which is based on a successive combination of requirements and services, we provide a practical applicable approach that works fully automatically. We show the applicability of our approach using three case studies in which medical devices interact with each other.

Mit der stetigen Konsolidierung der Web Service Standards vollzieht sich in der Diskussion zu serviceorientierten Architekturen ein Wechsel weg von der Implementierung und dem Deployment von Services hin zum Service Management. Die Indikatoren: Anzahl der Standardisierungsanfragen und die Menge großer Forschungsprogramme in diesem Bereich sind evident für einen wachsenden Bedarf an Managementmethoden für die Abbildung von Geschäftsanforderungen auf Servicekompositionen. Die Verwendung von semiformalen Modellen sowie die verteilte Entwicklung von SOA Services machen eine an Konventionen orientierte konstruktive Einschränkung der Freiheitsgrade bei der Prozess- und Servicemodellierung notwendig. In dieser Arbeit wird eine generische Methode vorgestellt, welche durch die Einführung von „Beschreibungsrahmen“ (Description Kits) sowohl eine Einschränkung der Modellierungsfreiheit in Bezug auf natürlichsprachliche Aspekte in fachkonzeptuellen Modellen erlaubt, als auch eine restriktive Benutzung bestehender Modellierungssprachen ermöglicht. Als Anwendungsfall wird die Konfiguration serviceorientierter Architekturen diskutiert. - (Die Dissertation ist veröffentlicht im Logos Verlag Berlin GmbH, http://www.logos-verlag.de, ISBN: 978-3-8325-2402-9) / With Service-oriented Architectures (SOA) companies are facing a paradigm shift towards services as the key unit of their enterprise architectures. An exploitation of the potential of Service-oriented Architectures is up to the applicability of semi-formal business models for a transformation into service compositions. However, several conceptual shortcomings prevent semi-formal models from being a suitable resource of an automated transformation process. Problems result from a multitude of modeling aims, objects, and procedures. Enhancements in order to solve these problems require both systematic preparation, and a methodical approach. This thesis provides a modeling method for business process-oriented SOA design using a meta-model based approach. An integrated modeling environment gives an overview of business requirements and allows appropriate assignment of SOA services to the business functions at the same time. The research refers to the example of process-oriented analysis and optimization of administrative procedures in German universities.

Mit der stetigen Konsolidierung der Web Service Standards vollzieht sich in der Diskussion zu serviceorientierten Architekturen ein Wechsel weg von der Implementierung und dem Deployment von Services hin zum Service Management. Die Indikatoren: Anzahl der Standardisierungsanfragen und die Menge großer Forschungsprogramme in diesem Bereich sind evident für einen wachsenden Bedarf an Managementmethoden für die Abbildung von Geschäftsanforderungen auf Servicekompositionen. Die Verwendung von semiformalen Modellen sowie die verteilte Entwicklung von SOA Services machen eine an Konventionen orientierte konstruktive Einschränkung der Freiheitsgrade bei der Prozess- und Servicemodellierung notwendig. In dieser Arbeit wird eine generische Methode vorgestellt, welche durch die Einführung von „Beschreibungsrahmen“ (Description Kits) sowohl eine Einschränkung der Modellierungsfreiheit in Bezug auf natürlichsprachliche Aspekte in fachkonzeptuellen Modellen erlaubt, als auch eine restriktive Benutzung bestehender Modellierungssprachen ermöglicht. Als Anwendungsfall wird die Konfiguration serviceorientierter Architekturen diskutiert. - (Die Dissertation ist veröffentlicht im Logos Verlag Berlin GmbH, http://www.logos-verlag.de, ISBN: 978-3-8325-2402-9) / With Service-oriented Architectures (SOA) companies are facing a paradigm shift towards services as the key unit of their enterprise architectures. An exploitation of the potential of Service-oriented Architectures is up to the applicability of semi-formal business models for a transformation into service compositions. However, several conceptual shortcomings prevent semi-formal models from being a suitable resource of an automated transformation process. Problems result from a multitude of modeling aims, objects, and procedures. Enhancements in order to solve these problems require both systematic preparation, and a methodical approach. This thesis provides a modeling method for business process-oriented SOA design using a meta-model based approach. An integrated modeling environment gives an overview of business requirements and allows appropriate assignment of SOA services to the business functions at the same time. The research refers to the example of process-oriented analysis and optimization of administrative procedures in German universities.