  Context information has emerged as an important resource to enable autonomy
and flexibility of pervasive applications. The widespread use of context
information necessitates efficient wide-area lookup services. In this paper, we
present the design and implementation of a peer-to-peer context lookup system
to support contextaware applications over multiple smart spaces. Our system
provides a distributed repository for context storage, and a semantic
peer-to-peer network for context lookup. Collaborative context-aware
applications that utilize different context information in multiple smart
spaces can be easily built by invoking a pull or push service provided by our
system. We outline the design and implementation of our system, and validate
our system through the development of cross-domain applications
