Abstract
Ambient assisted living (AAL) environments are augmented with sensing and communication technologies to support elderly people with personalized, adaptive and anticipatory requirements. A plethora of heterogeneous devices and services appear and disappear, which expose different behavior with the changing contexts in these environments. Therefore, a service matchmaking mechanism that attempts to identify relevant services in order to fulfill the user needs, has to deal with the heterogeneity of devices and services along with their dynamic behavior. Existing service specifications, such as semantic web services, are often used to abstract the environment's functionalities and the user tasks without incorporating context-aware properties, which makes them unsuitable for service matchmaking in pervasive and ambient environment. To deal with these issues, we introduce a contExt Aware web Service dEscription Language (wEASEL) that is an abstract service model to represent services and user tasks in AAL environments. Also, we present a set of wEASEL-based service matching algorithms and evaluate them for their suitability. The proposed service matchmaking mechanism can incorporate services that are available in local AAL environment as well as in the cloud computing marketplace.