Very interesting! Implementing a semi-index is very easy if you have implementations of Elias-Fano and balanced parentheses data structures. For Java I recomme

Very interesting! Implementing a semi-index is very easy if you have implementations of Elias-Fano and balanced parentheses data structures. For Java I recommend Sux4j [1] that has a very good implementation of Elias-Fano, but I think that balanced parentheses are very primitive. I was told by the author that a better data structure, based on Range-Min-Max trees, should be added soon. [1] http://sux.dsi.unimi.it/ http://sux.dsi.unimi.it/