Information Retrieval ! "#$%&' - PDF document

Information Retrieval �� !� "�#$%&�' � (�)��*��+�o��--./0� �1��2'��34�!� 45��678�' 4 8�# 9��:&; 4 "�#$%&;& �</=�)./05�>�o��0��/=�?.@��O�0�/.B��.o/� Yannis Tzitzikas University of Crete CS-463,Spring 05 �� ι�� : �ι�� ι�� • �ι�� • Lexical Analysis ( ��ι��ι�� ) • Stopwords ( ��ι� ��ι�� ) • Stemming ( �� ι�� ) – Manual – Table Lookup – Successor Variety – n-Grams – Affix Removal (Porter’s algorithm) CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 2 Retrieval 2005 1

�� ι�� • �� – !�� ι "�� ι ��ι� ��"� ��ι�� ι� �� ι�� ( ��ι�� ι� #�� ι��"�� "�� " �� ) • �� – ��ι� �� ( �� ) �� ι�� • ��"��ι �� – $�� ι�"�� (effectiveness) – $�� !��ι�"�� (efficiency) �� – �� CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 3 Retrieval 2005 %��ι� �� [ � ] ��ι��ι�� – ��&�ι�� , ��ω� , ��ω�� , ��ω� ��ω� , �� [ $ ] ��ι��"� �� (stopwords) – ��ι#� �� ι�� !ι��ι�ι�� ι��"�� ( �� , ��ω�� , �� ω�� , �� ) [ � ] �� (stemming) �� ι�� – ��ι#� ��ω� / ��ω� ( �� , �� , ��ι�� ) �ι� �� ι�� ι�� ι�� &�� [ ! ] ��ι�� ι��ι�� – �� ι $��ι �� "�� ( ��ι��ι�� , �� , ��ι�� , �� ) CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 4 Retrieval 2005 2

%��ι� �� ( '' ) ��" �� "�� Accents Noun Manual Docs stopwords stemming spacing groups indexing structure structure Full text Index terms CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 5 Retrieval 2005 [ � ] �� η (Lexical Analysis) ��"� : identify tokens – ��&�ι�� , ��ω� , ��ω�� , ��ω� ��ω� , �� ι��&��ι� �� ι�� : – ��ι� �� ι�� (�#�� • O2, $ι�� ) 6, ) 12 – �� (hyphens) • “state of the art” vs “state-of-the-art” • “Jean-Luc Hainaut”, “Jean-Roch Meurisse”, F-16, MS-DOS – �� (punctuations) • OS/2, .NET, command.com – *ι�� - ��#�� • �� "�� ι �� ι�� CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 6 Retrieval 2005 3

[ � ] ��ι��ι�� (II) • ��ι��ι�� ι� ��ι� – +�� ι �ι� �� , �� &�ι�� • AND, OR, NOT, proximity operators, regular expressions, etc • ,�"��ι �� "� ��ι��ι�� – ( � ) use a lexical analyzer generator (like lex) • best choice if there are complex cases – (b) write a lexical analyzer by hand ad hoc, • worse choice (error prone) – (c) write a lexical analyzer by hand as a finite state machine CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 7 Retrieval 2005 [ $ ] Stopwords ( ��ι� ��ι�� ) ��ι#� �� ι�� !ι��ι�ι�� ι��"�� ( �� , ��ω�� , �� ω�� , �� ) – e.g. “a”, “the”, “in”, “to”; pronouns: “I”, “he”, “she”, “it”. • -#�� – �� ( �� ι 40%) • ��ι� – -ι ��ι� ��ι�� &��ι ��" �� &�� ι �� – Not every frequent english word should be in the list • Top 200 English words include «time, war, home, life, water, world» • In a CS corpus we could add to the stoplist the words: «computer, program, source, machine, language» • ��$�� – q=“ to be or not to be ” – ( �ι� �� "�� " ��ι�� *�� .�� '�� !�� ) CS-463, Information Yannis Tzitzikas, U. of Crete, Spring 8 Retrieval 2005 4

Information Retrieval ! "#$%&' - PDF document

Information Retrieval ! "#$%&' ()*+o--./0 12'34! 45678' 4 8# 9:&; 4 "#$%&;&

Information Retrieval Introducing Information Retrieval and Web Search Information Retrieval

1 What is multimedia information retrieval? 1.1 Information retrieval 1.2 Multimedia 1.3

CS54701: Information Retrieval CS-54701 Information Retrieval Luo Si Department of Computer

Information Retrieval Introducing Information Retrieval and Web Search

Information Retrieval CS-7961: Topics in Information retrieval (IR) is finding material (usually

Information Retrieval CS276: Information Retrieval and Web Search

Information Retrieval CS276: Information Retrieval and Web Search

Introduction Information Retrieval Indian Statistical Institute Information Retrieval (ISI)

Probabilistic Information Retrieval CE-324: Modern Information Retrieval Sharif University of

Web Information Retrieval Lecture 9 Information Retrieval in the Web Search use (iProspect

Information Retrieval CS276: Information Retrieval and Web Search Pandu

Information Retrieval CS276: Information Retrieval and Web Search Pandu

Information Retrieval CS276 Information Retrieval and Web Search Christopher

Information Retrieval Modeling Russian Summer School in Information Retrieval Djoerd Hiemstra

Web Information Retrieval Lecture 8 Evaluation in information retrieval Recap of the last

Information Retrieval CS276: Information Retrieval and Web Search Text Classification 1 Chris

Le projet ILC/ILD/CALICE CS du LPSC-Grenoble du 22 juin 2017 J.-y. Hostachy - D. Grondin J.

Dtection et reconnaissance visuelle temps-rel dobjets dune catgorie (pitons,

Graphviz rendu facile avec GvGen Sbastien Tricaud PyCon FR 2008 Sbastien Tricaud Graphviz

Duce: un aper cu Alain Frisch INRIA Rocquencourt 15 octobre 2004 GT Cristal Duce: un

NAES Webinar New Heads Introduction to Episcopal Schools 2020 August 2020 Welcome! All

Late binding Ch 15.3 Highlights - Late binding for variables - Late binding for functions

Phases of Disaster Despair Threat Threat Phase: Small events serve as a warning or threat to

1 2 3 Loneliness is real and is not imagined as it is widespread in the church. Most people do