{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:11:01Z","timestamp":1760242261015,"version":"build-2065373602"},"reference-count":21,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2017,2,22]],"date-time":"2017-02-22T00:00:00Z","timestamp":1487721600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Algorithms"],"abstract":"<jats:p>We address the problem of positional indexing in the natural language domain. The positional inverted index contains the information of the word positions. Thus, it is able to recover the original text file, which implies that it is not necessary to store the original file. Our Positional Inverted Self-Index (PISI) stores the word position gaps encoded by variable byte code. Inverted lists of single terms are combined into one inverted list that represents the backbone of the text file since it stores the sequence of the indexed words of the original file. The inverted list is synchronized with a presentation layer that stores separators, stop words, as well as variants of the indexed words. The Huffman coding is used to encode the presentation layer. The space complexity of the PISI inverted list is     O (  ( N \u2212 n )   \u2308  log  2 b   N \u2309  +  (  \u230a   N \u2212 n  \u03b1  \u230b  + n )  \u00d7  (  \u2308  log  2 b   n \u2309  + 1 )  )     where N is a number of stems, n is a number of unique stems, \u03b1 is a step\/period of the back pointers in the inverted list and b is the size of the word of computer memory given in bits. The space complexity of the presentation layer is     O ( \u2212  \u2211  i = 1  N   \u2308  log 2   p i  n ( i )   \u2309  \u2212  \u2211  j = 1   N \u2032    \u2308  log 2   p j \u2032  \u2309  + N )     with respect to     p i  n ( i )      as a probability of a stem variant at position i,     p j \u2032     as the probability of separator or stop word at position j and     N \u2032     as the number of separators and stop words.<\/jats:p>","DOI":"10.3390\/a10010030","type":"journal-article","created":{"date-parts":[[2017,2,22]],"date-time":"2017-02-22T11:36:58Z","timestamp":1487763418000},"page":"30","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Towards Efficient Positional Inverted Index \u2020"],"prefix":"10.3390","volume":"10","author":[{"given":"Petr","family":"Proch\u00e1zka","sequence":"first","affiliation":[{"name":"Department of Theoretical Computer Science, Faculty of Information Technology, Czech Technical University in Prague, Prague 16000, Czech Republic"},{"name":"Current address: Th\u00e1kurova 2700\/9, 16000 Praha 6, Czech Republic."}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3022-2694","authenticated-orcid":false,"given":"Jan","family":"Holub","sequence":"additional","affiliation":[{"name":"Department of Theoretical Computer Science, Faculty of Information Technology, Czech Technical University in Prague, Prague 16000, Czech Republic"},{"name":"Current address: Th\u00e1kurova 2700\/9, 16000 Praha 6, Czech Republic."}]}],"member":"1968","published-online":{"date-parts":[[2017,2,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Turpin, A., Tsegay, Y., Hawking, D., and Williams, H.E. 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