Retrieval-Update Speed Tradeoffs Using Combined Indices In a paper in the November 1970 Communications of the ACM, V. Y. Lum introduced a technique of file indexing named combined indices. This technique permitted decreased retrieval time at the cost of increased storage space. This paper examines combined indices under conditions of file usage with different fractions of retrieval and update. Tradeoff curves are developed to show minimal cost of file usage by grouping various partially combined indices. CACM December, 1971 Mullin, J. K. file organization, combined index files, inverted files, information retrieval, query, multi-attribute retrieval, file update 3.73 3.74 3.79 CA711203 JB February 2, 1978 10:18 AM 2140 4 2140 2452 4 2140 2765 4 2140 2901 4 2140 3134 4 2140 1976 5 2140 2140 5 2140 2140 5 2140 2140 5 2140