  Pervasive services may be defined as services that are available "to any
client (anytime, anywhere)". Here we focus on the software and network
infrastructure required to support pervasive contextual services operating over
a wide area. One of the key requirements is a matching service capable of
as-similating and filtering information from various sources and determining
matches relevant to those services. We consider some of the challenges in
engineering a globally distributed matching service that is scalable,
manageable, and able to evolve incrementally as usage patterns, data formats,
services, network topologies and deployment technologies change. We outline an
approach based on the use of a peer-to-peer architecture to distribute user
events and data, and to support the deployment and evolution of the
infrastructure itself.
