A five-year effort under the Ada Joint Program Office has developed a proposed standard for a host system interface as seen by tools running in an Ada Programming Support Environment (APSE). Standardization of this interface as DOD-STD-1838A will have a number of desirable effects for the Department of Defense, including tool portability, tool integration, data transportability, encouragement of a market in portable tools, and better programmer productivity. As the capability of tools to communicate with each other is a central requirement in APSEs, the Common APSE Interface Set (CAIS) has paid particular attention to facilitate such communication in a host-independent fashion. CAIS incorporates a well-integrated set of concepts tuned to the needs of writers and users of integrated tool sets. This paper covers several of these concepts: the entity management system used in place of a traditional filing system, object typing with inheritance, process control including atomic transactions, access control and security, input/output methods, support for distributed resource control, and facilities for inter-system data transport
