NDLI: Word-based self-indexes for natural language text

Content Provider	ACM Digital Library
Author	Fariña, Antonio Places, Ángeles S. Brisaboa, Nieves R. Rodríguez, Eduardo Claude, Francisco Navarro, Gonzalo
Copyright Year	2012
Abstract	The inverted index supports efficient full-text searches on natural language text collections. It requires some extra space over the compressed text that can be traded for search speed. It is usually fast for single-word searches, yet phrase searches require more expensive intersections. In this article we introduce a different kind of index. It replaces the text using essentially the same space required by the compressed text alone (compression ratio around 35%). Within this space it supports not only decompression of arbitrary passages, but efficient word and phrase searches. Searches are orders of magnitude faster than those over inverted indexes when looking for phrases, and still faster on single-word searches when little space is available. Our new indexes are particularly fast at $\textit{counting}$ the occurrences of words or phrases. This is useful for computing relevance of words or phrases. We adapt $\textit{self-indexes}$ that succeeded in indexing arbitrary strings within compressed space to deal with large alphabets. Natural language texts are then regarded as sequences of words, not characters, to achieve word-based self-indexes. We design an architecture that separates the $\textit{searchable}$ sequence from its $\textit{presentation}$ aspects. This permits applying case folding, stemming, removing stopwords, etc. as is usual on inverted indexes.
Starting Page	1
Ending Page	34
Page Count	34
File Format	PDF
ISSN	10468188
e-ISSN	15582868
DOI	10.1145/2094072.2094073
Volume Number	30
Issue Number	1
Journal	ACM Transactions on Information Systems (TOIS)
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	2012-03-06
Publisher Place	New York
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Self-indexes Compressed data structures Inverted indexes
Content Type	Text
Resource Type	Article
Subject	Computer Science Applications Information Systems Business, Management and Accounting

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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