Mobile Hosts in Enterprise Service Integration Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von Master of Science (M.Sc.) Satish Narayana Srirama aus Peddapadmapuram, A.P., India Berichter: Universitätsprofessor Dr. Matthias Jarke, RWTH Aachen Universitätsprofessor Dr. Wolfgang Nejdl, TU Hannover Tag der mündlichen Prüfung: 19. September 2008 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar. iii Abstract Basic web services are widely being accessed from smart phones due to the advances in wireless devices and mobile communication technologies. While such mobile web service (MWS) clients are common, the thesis addresses the scope of providing web services from smart phones, thus integrating personalized mobile services into cellular enterprises and Internet. A ‘Mobile Host’ capable of providing basic web services from smart phones was developed and the performance analysis of the tool proved the technical feasibility of the concept. Service delivery and management from Mobile Host are now technically feasible. How- ever, the ability to provide proper quality of service (QoS) for the Mobile Host is observed to be very critical, especially in terms of security and reasonable scalability. In the security analysis, the adaptability of the WS- Security specification to the mobile web service provisioning (MWSP) domain is analyzed. The scalability analysis tried to reduce the size of the MWS messages being transmitted by means of different compression technologies. The analyses mainly focused on additional latencies caused to the performance of the Mobile Host by the added QoS features. Mobile Host finds its use in domains like mobile community support, collaborative learning, social systems etc. The smart phone can act as a multi-user device without additional manual effort on part of the mobile user. The thesis extensively studied the appli- cations of Mobile Host in the m-learning domain and developed the MobileHost CoLearn system, as a tool helping in the collaborative learning process. The user evaluation of the system clearly showed the adaptability of Mobile Hosts by different communities. The huge number of web services possible, with each Mobile Host providing some services in the wireless network, makes the discovery of these services quite complex. The traditional centralized UDDI (Universal Description, Discovery and Integration) based registries are not adaptable, as they can have bottlenecks and can make single points of failure. Moreover, the dynamic nature of the mobile nodes makes the binding information change regularly, thus leaving many stale advertisements in the registry. Hence a dynamic MWS discovery mechanism is proposed, that uses the peer to peer network and its features for publishing and discovery of mobile web services. Based on Mobile Host’s application, QoS and discovery research, the deployment scenario of the Mobile Hosts in cellular networks is identified. A ‘Mobile Web Ser- vices Mediation Framework (MWSMF)’ is established as an intermediary between the web service clients and the Mobile Hosts, based on the Enterprise Service Bus (ESB) technology. v Kurzfassung Durch neuere Entwicklungen im Bereich mobiler Geräte haben einfache Web Services, die von Smart Phones aus verwendet werden können, weite Verbreitung gefunden. Während aber MWS Clients bereits weit verbreitet sind, befasst sich diese Arbeit mit der Prob- lematik, Web Services auf Smart Phones bereitzustellen, also mit der Integration personal- isierter mobiler Dienste in Mobilfunknetze und das Internet. Es wurde ein ‘Mobile Host’ entwickelt, der es ermöglicht, einfache Web Services durch Smart Phones anzubieten. Die Performanz-Analyse des Systems hat die technische Machbarkeit des Konzepts bewiesen. Bereitstellung und Verwaltung von Diensten auf mobilen Geräten sind nun technisch machbar. Es hat sich allerdings gezeigt, dass es für den Mobile Host von besonderer Be- deutung ist, eine angemessene Dienst-Qualität (QoS, "quality of service") zu garantieren, insbesondere in Bezug auf Sicherheit und Skalierbarkeit. Bei der Sicherheitsanalyse wurde die Anpassbarkeit der WS-Security-Spezifikation an den Bereich der Bereitstel- lung mobiler Web Services (mobile web service provisioning, MWSP) analysiert. In der Skalierbarkeitsanalyse wurde mit Hilfe verschiedener Komprimierungstechniken versucht, die Größe der übermittelten MWS-Nachrichten zu reduzieren. Der Fokus der Analyse wurde auf die zusätzlichen Latenzzeiten im Mobile Host gelegt, die durch die QoS Merkmale verursacht werden. Anwendungen für Mobile Hosts lassen sich unter anderem in den Bereichen Mobile Community Support, Collaborative Learning und Social Systems finden. Das Smart Phone kann ohne zusätzlichen manuellen Aufwand durch den Anwender als Mehr-Benutzer- Gerät agieren. Im Rahmen der Arbeit wurden Anwendungen für Mobile Hosts im Bereich des m-learning untersucht. So wurde das MobileHost CoLearn System als Werkzeug zur Unterstützung des kollaborativen Lernprozesses entwickelt. Die Nutzer-Evaluaierung des Systems hat die Anpassbarkeit von Mobile Hosts durch verschiedene Communities klar gezeigt. Die hohe Zahl möglicher Web Services, wobei jeder Mobile Host mehrere Dienste im Netzwerk anbieten kann, macht die Ermittlung (discovery) dieser Dienste sehr komplex. Traditionelle zentralisierte UDDI-basierte (Universal Description, Discovery and Inte- gration) registries sind nicht anpassbar, da sie Flaschenhälse aufweisen können und als ’single point of failure’ anfällig sind. Des Weiteren erfordert die dynamische Natur von mobilen Knoten regelmäßige Änderungen der Information über Dienste, wodurch viele veraltete Advertisements in der Registrierung zu finden sind. Daher wird alternativ ein dynamischer MWS-discovery-Mechanismus vorgestellt, der das Peer-to-Peer Netzwerk und seine Merkmale für Publishing und Discovery von Mobile Web Services nutzt. Auf Grundlage bestehender Forschung zu Anwendungen, QoS und Discovery von Mobile Hosts wird ein Deployment-Szenario für Mobile Hosts in Mobilfunknetzen identifiziert. Basierend auf der Enterprise-Service-Bus-Technologie (ESB) wird ein ‘Mobile Web Services Mediation Framework (MWSMF)’ als Schnittstelle zwischen den Web Service Clients und den Mobile Hosts eingeführt. vii Acknowledgements Ever since my engineering days, I always wanted to pursue higher education and head for Doctorate degree. I am fortunate that I could achieve this goal at such a prestigious institute as Rheinisch-Westfaelische Technische Hochschule Aachen (RWTH Aachen). There are several people without whom this dream would not have been a reality. I would like to express my deep and sincere gratitude to all those involved. First of all, I thank Prof. Matthias Jarke for all the support he has extended me, during the past six years. I would also like to thank him for all the confidence he had shown, in me and my work. Secondly, I thank Prof. Wolfgang Nejdl for reviewing the thesis and being my second examiner. Nonetheless I would also like to thank Prof. Wolfgang Prinz and owe him lots of gratitude for having shown me this way of research. I would also like to thank Friedhelm Ramme, Roman Levenshteyn and Martin Gerdes of Ericsson Research for their help and support, during the research. I am especially thankful to Roman Levenshteyn for all his advice, positive criticism, and willingness to discuss any questions or ideas that I have had, during the past years. I would also like to thank all my co-authors: Prof. Matthias Jarke, Prof. Wolfgang Prinz, Mohamed Amine Chatti, David Kensche, Yiwei Cao, Dr. Ralf Klamma, Anton Naumenko, Pravin Pawar, Bert-Jan van Beijnum, Aart van Halteren, Iliyana Ivanova, Hongyan Zhu, Kiran Kumar Pendyala, Kaifei Wang, Rajsekhar Kakumani, Akshaia Aggarwal and Prof. Vagan Terziyan. I am thankful to all my students, whose work contributed my research. The work was initially sponsored by Graduiertenkollegs - "Software für mobile Kom- munikationssysteme" at RWTH Aachen, later by Ultra High-Speed Mobile Information and Communication (UMIC) excellence research cluster, established under the excellence initiative of the German government, and partly supported by Ericsson research. I thank all the funding agencies and appreciate their financial support for my projects. I am also grateful to the Information Systems & Databases Group, at RWTH Aachen for providing me an excellent work environment during the past years. I thank all my colleagues, a slight banter with whom, always made me better focused. I sincerely thank my parents for their never ending support and especially my father, Prof. Lakshminarayana Srirama, for being an inspiration and role model. The blessings of my mother Lolakshi Srirama and the encouragement of my brother Jagadeesh Narayana Srirama, sister Ambika Meesala and brother-in-law Ramesh Naidu Meesala are sincerely acknowledged. Special thanks are to my beloved wife, Gayatri, for her compassion and patience during the last days of my dissertation. Finally I like to thank my friends and relatives for having them on my side, especially Pravin Pawar and Prof. Lakshmana Das Nadukuru for our fruitful discussions before considering the doctoral studies. Aachen Satish Narayana Srirama 22nd September, 2008 Contents Abstract iii Kurzfassung v Acknowledgements vii Contents ix List of Figures xii List of Tables xv 1 Introduction 1 1.1 Motivation . .1 1.2 Contributions