2140	 Retrieval-Update Speed Tradeoffs Using Combined Indices	 In a paper in the November 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. file organization combined index files inverted files information retrieval query multi-attribute retrieval file update
