A context-aware service in ubiquitous computing environments aims to supply services according to a user?s situation information that is dynamically occurring. The existing context-aware workflow systems provide a contextaware service based on a workflow that uses a user?s situation information as services?s transition condition. But they can?t apply user?s new service demands, which may be dynamically occurring even when a workflow is on going, to the workflow scenario.

In this paper we propose a context-aware workflow system that can reconstruct autonomously and efficiently an initial workflow scenario according to user?s dynamic service demands, and can adopt the new service demands into the initial workflow scenario without interrupting or deleting the on-going workflow services. The proposed system uses an incremental parsing method to provide contextaware services without interrupting of service through recognizing exactly the place holder that has to be changed in a workflow scenario and reconstructing only the part under the influence of the changes. Therefore, a user can apply his new service demands to a scenario document regardless of the time and the space, and he can be guaranteed to support the continuous execution of a context-aware service without the discontinuance of services according to the workflow scenario, which describes the new service demands.