The advent of wireless networking technologies in combination with the decreasing size of yet more powerful computing devices have led to the emergence of new applications to be deployed in mobile environments. Users equipped with mobile devices are able to spontaneously collaborate with each other in an ad-hoc manner. However, when deploying cooperative applications in mobile environments, one has to provide suitable means to cope with the characteristics of these environments. Due to the

more »

... ity of participants and the wireless networking technologies, mobile networks are more dynamic than fixed networks. As resources of mobile networks expose a temporary nature, failures of any kind are no longer the exceptional case. Suitable forward error-handling mechanisms which still allow for successful execution of an application in case of failure, as well as backward failure-recovery mechanisms, which avoid inconsistent system states, have to be integrated. In this thesis, an integrated approach of transactional support of ad-hoc collaborations with service discovery in mobile environments is presented. The objective is to ensure reliable support while respecting the autonomy of mobile devices. Ad-hoc collaborations are implemented as service compositions, specified as workflows. We present a service discovery protocol for ad-hoc scenarios which exploits the mobility of nodes: It adapts to the current context of nodes and thereby ensures high availability of information and decreases the number of messages if possible. On the other hand, it enables discovery and usage of remote services which are not in the direct vicinity of nodes. This protocol builds the foundation for ad-hoc collaboration, as composition at runtime is only possible, if services may be discovered in the first place. On the other hand, it allows for forward failure-handling, as it enables finding of alternatives. The core contribution of this thesis is an adaptive workflow management system: It explores transactional properties of services and empl [...]