Indexing of static and dynamic sets is fundamental to a large set of applications such as information retrieval and caching. Denoting the characteristic vector of the set by B, we consider the problem of encoding sets and multisets to support approximate versions of the operations rank(i) (i.e., computing sum_{j <= i} B[j]) and select(i) (i.e., finding min{p|rank(p) >= i}) queries. We study multiple types of approximations (allowing an error in the query or the result) and present lower bounds and succinct data structures for several variants of the problem. We also extend our model to sliding windows, in which we process a stream of elements and compute suffix sums. This is a generalization of the window summation problem that allows the user to specify the window size at query time. Here, we provide an algorithm that supports updates and queries in constant time while requiring just (1+o(1)) factor more space than the fixed-window summation algorithms.
@InProceedings{benbasat_et_al:LIPIcs.ISAAC.2018.54, author = {Ben Basat, Ran and Jo, Seungbum and Satti, Srinivasa Rao and Ugare, Shubham}, title = {{Approximate Query Processing over Static Sets and Sliding Windows}}, booktitle = {29th International Symposium on Algorithms and Computation (ISAAC 2018)}, pages = {54:1--54:12}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-094-1}, ISSN = {1868-8969}, year = {2018}, volume = {123}, editor = {Hsu, Wen-Lian and Lee, Der-Tsai and Liao, Chung-Shou}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2018.54}, URN = {urn:nbn:de:0030-drops-100027}, doi = {10.4230/LIPIcs.ISAAC.2018.54}, annote = {Keywords: Streaming, Algorithms, Sliding window, Lower bounds} }
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