The Mach 3.0 micro-kernel provides a foundation for the emulation of various operating systems with a combination of libraries and Mach servers. We present a general-purpose naming facility to help construct such emulation systems by assembling many independent servers. This facility defines a set of standard interfaces for a uniform name space with uniform access mediation and a set of practical mechanisms to integrate servers into this name space, through prefix tables and ancillary servers supporting special mount points. We then discuss the application of this facility to UNIX 4.3 BSD emulation, to a secure system with a centralized trusted name server, and to larger distributed systems.