Moore, R. C. (1979). Handling complex queries in a distributed data base. SRI INTERNATIONAL MENLO PARK CA.
As part of the continuing development of the LADDER system  , we have substantially expanded the capabilities of the data base access component that serves as the interface between the natural-language front end of LADDER and the data base management systems on which the data is actually stored. SODA, the new data base access component, goes beyond its predecessor IDA , in that it accepts a wider range of queries and accesses multiple DBMSs. This paper is concerned with the first of these areas, and discusses how the expressive power of the query language was increased, how these changes affected query processing in a distributed data base, as well as what are some limitations of and planned extensions to the current system.