1194	 Establishment of the ACM Repository and Principles of the IR System Applied to its Operation	 The history of the establishment of the ACM Repository at the Moore School University of Pennsylvania is reviewed briefly. Two principles are presented as paramount in the provision of information services easy accessibility to the information files by users unfamiliar with file organization and value of service exceeding user costs. These principles serve as guides in mechanizing the ACM Repository. The main features of the information system are direct user access via on-line teletypewriter console direct user access to all details of the system organization unrestricted and expandable search vocabulary user access through many facets of document indexing and stochastic search through linked index terms and other file relationships. The first contribution to the ACM Repository consisted of documents relating primarily to early research on compilers. These documents have been cataloged and indexed and the catalog is scheduled to appear in Computing Reviews. The indexing system is described in detail. The Main Catalog is used to describe the documents and inverted lists are provided by the Repository system for retrieval by concept coordination.
