- Slides: 11
Search Techniques Boolean Logic and Keyword Searching
Information Retrieval • Catalogues, index, subject directories, lists, etc. • Field searches, keyword and sections searches, etc. • Full-text search In text retrieval, full text search refers to a technique for searching a computer-stored document or database. In a full text search, the search engine examines all of the words in every stored document as it tries to match search words supplied by the user. • NB! The perfect one-stop-legal-research-shop/tool does not exist. Do not bother looking for it. Rather focus on learning about the limitations and advantages of each research option.
Issues • Ambiguities of natural language make full-text search less precise • A free-text search is likely to retrieve many documents which are irrelevant to the search question But • These can be overcome by using advanced search techniques to structure machineunderstandable queries
Advanced Search Techniques • Boolean logic and keyword searching Keyword searching refers to a search type in which you enter terms representing the concepts you wish to retrieve. Boolean operators are not used. Boolean logic refers to a search in which symbols are used to represent Boolean logical operators. In this type of search on the Internet, the absence of a symbol is also significant, as the space between keywords defaults to either OR logic or AND logic. Many popular search engines traditionally defaulted to OR logic, but as a rule are moving away from the practice and defaulting to AND. Implied Boolean logic has become so common in Web searching that it may be considered a de facto standard.
Boolean Operators • • Boolean logic (named after Irish mathematician George Boole) Logical operators: OR AND NOT e. g. I want info on college Find synonyms: college, university, campus e. g. I am interested in the relationship between poverty and crime e. g. I want info on cats but don’t want to read anything about dogs
Examples of Boolean Logic • I would like to find out about cases/articles dealing with the right of parents of pupils to be exempt from paying school fees. Pupil, student School, but not university and not technicon Parent, or guardian (pupil OR student) AND (school NOT university NOT technicon) AND (parent or guardian) AND fee?
Implied Boolean Keyword Search I. Query: I need information about university. Boolean logic: OR Search: university college Note: AND / OR II. Query: I'm interested in dyslexia in adults. Boolean logic: AND Search: +dyslexia +adults III. Query: I'm interested in radiation, but not nuclear radiation. Boolean logic: NOT Search: radiation -nuclear IV. Query: I want to learn about cat behavior. Boolean logic: OR, AND Search: cats felines +behavior
Advanced Search Techniques • Search for phrases within quotations e. g. “death penalty” • Proximity operators (e. g. NEAR) • Field searching e. g. TITLE: slavery (http: //www. altavista. com/) DEFINE: slavery (http: //www. google. co. za/) Quick Tip! Best Bet Search Syntax Place the plus sign ( + ) in front of all words you wish to retrieve +influenza +birds Place a phrase within quotations "freedom of the press" Putting it all together: +“crime rate" +“South Africa"
Advanced Search Techniques • Truncation – searching for words with the same root (e. g. work! or work? (Sabinet), fetches work, worker, workforce, workplace, etc. ) • Plurals – e. g. school+ will find school or schools • Wildcards – to retrieve variant spellings - e. g. Sabinet wom#n will return woman and women; LN wom? n will return woman and women • Proximity – type a character between search terms to specify that records found contain both terms, in order typed with no more than specified number of words between them e. g. online w 3 system • Might differ from database to database – check the help files!
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