The DOMAIN system is an architecture for networks of personal workstations and servers which creates an integrated distributed computing environment. Its distinctive features include: a network-wide file system of objects addressed by unique identifiers (UID's); the abstraction of a single level store for transparently accessing all objects, regardless of their location in the network; and a network-wide hierarchical name space. The implementations of these facilities exhibit several interesting approaches to layering the system software. In addition to network transparent data access, interprocess communication is provided as a basis for constructing distributed applications; as a result, we have some experience to guide the choice between these two alternative implementation techniques. Networks utilizing this architecture have been Operational for almost three years; some experience with it and lessons derived from that experience are presented, as are some performance data.