In addition to constructing a new dictionary structure for each block and eliminating the expensive sorting step, SPIMI has a third important component: compression. Both the postings and the dictionary terms can be stored compactly on disk if we employ compression. Compression increases the efficiency of the algorithm further because we can process even larger blocks, and because the individua lblocks require less space on disk. We refer readers to the literature for this aspect of the algorithm (Section 4.7).