Importance of Cholesterol in Biomedical Context
Cholesterol, a vital lipid in tissues and plasma, plays key roles in membrane structure, steroid synthesis, and metabolic processes. Understanding its regulation and synthesis is crucial for managing health risks associated with cholesterol metabolism.
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INFORMATION RETRIEVAL INFORMATION RETRIEVAL TECHNIQUES TECHNIQUES BY DR. ADNAN ABID Lecture # 18 Wild Card Queries B Tree 1
ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS The presentation of this lecture has been taken from the underline sources 1. Introduction to information retrieval by Prabhakar Raghavan, Christopher D. Manning, and Hinrich Sch tze 2. Managing gigabytes by Ian H. Witten, Alistair Moffat, Timothy C. Bell 3. Modern information retrieval by Baeza-Yates Ricardo, 4. Web Information Retrieval by Stefano Ceri, Alessandro Bozzon, Marco Brambilla
Outline Outline How to Handle Wild-Card Queries Wild-card queries: * B-Tree B+ Tree 3
How to Handle Wild How to Handle Wild- -Card Queries Card Queries B-Trees Permuterm Index K-Grams Soundex Algorithms 4
Wild Wild- -card queries: * card queries: * mon*:find all docs containing any word beginning with mon . Easy with binary tree (or B-tree) lexicon: retrieve all words in range: mon w < moo *mon: find words ending in mon : harder Maintain an additional B-tree for terms backwards. Can retrieve all words in range: nom w < non. Exercise: from this, how can we enumerate all terms meeting the wild-card query pro*cent? 5
B B- -Tree Tree 6
B B- -Tree Tree Level 0 A Level 1 B C D Level 2 E F G H I Level 3 J K n = # of pairs. # of external nodes = n + 1. 7
Wild Wild- -card queries: * card queries: * mon*:find all docs containing any word beginning with mon . Easy with binary tree (or B-tree) lexicon: retrieve all words in range: mon w < moo *mon: find words ending in mon : harder Maintain an additional B-tree for terms backwards. Can retrieve all words in range: nom w < non. Exercise: from this, how can we enumerate all terms meeting the wild-card query pro*cent? 8
B+ Tree B+ Tree 9
Wild Wild- -card queries card queries example example Query Sanat* AND Jayasur* Sanat AND Jayasur Query mo*y *day Queries: X lookup on X$ *X lookup on X$* X*Y lookup on Y$X* yad* X* lookup on $X* *X* lookup on X* X*Y*Z ??? Exercise! 10
Resources Resources IIR 3, MG 4.2 Efficient spell retrieval: K. Kukich. Techniques for automatically correcting words in text. ACM Computing Surveys 24(4), Dec 1992. J. Zobel and P. Dart. Finding approximate matches in large lexicons. Software - practice and experience 25(3), March 1995. http://citeseer.ist.psu.edu/zobel95finding.html Mikael Tillenius: Efficient Generation and Ranking of Spelling Error Corrections. Master s thesis at Sweden s Royal Institute of Technology. http://citeseer.ist.psu.edu/179155.html Nice, easy reading on spell correction: Peter Norvig: How to write a spelling corrector http://norvig.com/spell-correct.html 11
