Ubiquitous computing applications exploit context information to adapt their services in accordance with users needs based on information sensed both from the physical and computational environment. We advocate that context -aware applications can take advantage of the benefits provided by Web Services in particular, alleviating diferences in heterogeneous ubiquitous environments and apportioning responsibilities between applications and infrastructures. We present the Context Kernel Web Service that illustrates how such a service could be built at the same time that leverages dimensions for context information proposed in the literature. The Context Kernel as a Web Service allows applications not only to store and retrieve, but also to exchange context information through the Web.