In the context-aware services, a context activates services for the user and is subject to a certain duration of validity, which we call a context lifecycle in this thesis. Existing context management researches use Event-Condition-Action (ECA) policy by simply assuming that contexts are generated and terminated in one-after-another fashion. We observed, however, the possibilities of multiple contexts (i.e. situations) that are active in the common time frame, which allows that a new context may not only be terminated but temporarily deactivated or even co-active with the previous context depending on the context relationships between them. Their corresponding services are also required to adapt themselves accordingly along with the lifecycles of the contexts thus implementing more sophisticated user services. In this thesis, we propose a context lifecycle management scheme based on an extended ECA policy, called Event-Condition-(context)State-Action (ECSA). The proposed scheme has been imported into our context management system. We also show how the proposed idea suits more sophisticated context-aware services in ubiquitous computing environments.