A method is presented for extending a conventional DBMS (database management system) for geographic applications. The interface language SQL is augmented to allow formulation of queries involving both spatial and nonspatial selection criteria. A novel indexing structure is supported to facilitate query retrieval that is based on spatial proximity. To enable hybrid queries to be evaluated efficiently, an extended optimization strategy is proposed that evaluates minimal implementation effort.>

Directory Systems to support communications networks are currently the subject of serious international standardization efforts. The most recent CCITT and ISO proposals for Directory Systems are summarized, and within this context the requirements for flexible and robust access control mechanisms are examined. The existence of varied access control policies at the international, national and local levels and the need to maintain the integrity of Directory System information are identified as major factors determining access control procedures. Techniques are suggested for access control mechanisms capable of capturing and enforcing the relevant access control semantics at each network site.

A working implementation of an inverted index suitable for real time applications is described. Based upon a hash addressed random access organization with variable length records, the index structure and processing algorithms were developed with the aid of a simulation model. Some typical simulation results are presented and critical parameters identified. One solution to the inverted key identification problem is proposed, although a severe time penalty accrues from designing software which is not directly dependent upon the main file record format.