In ubiquitous computing environments, context-awareness is one of the most important research topics. Computers embedded in our surrounding can extract information about a user, and the information makes it possible to offer personalized services according to the user's preference. To extract a large amount of context information, wearable sensor devices will become more important in the near future. However, it is not easy to develop context-aware services that use context information from wearable sensor devices because of the gap between low-level sensor information and high-level context that the services require. In this paper, we propose a software infrastructure for wearable sensor networks. We first discuss the requirements to retrieve context information from wearable sensor networks. Then, we introduce our software infrastructure named Cinnamon that extracts high-level context from low-level context information retrieved from wearable sensor networks. The software infrastructure makes it dramatically easy to develop context-aware services for wearable sensor networks. We present the design and implementation of Cinnamon, and discuss our current prototype implementation.