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Boole, George English mathematician born in 1815, died 1864. Appointed to the Chair of Mathematics, Queens College, Cork, Ireland, in 1849. Boole reduced logic to algebraic terms and would give his name to such computer-related phrases as boolean logic, boolean searching, and boolean operators
boolean logic The use of boolean operators, governed by algebraic rules, to delineate and refine a computer search. Boolean logic holds that search operations will occur in a set pattern; for example, statements inside parentheses will be dealt with first, followed by not statements, then by and statements, and then by or statements. Thus, according to boolean logic, the search: water and pollution or air and pollution is equivalent to the search (water and pollution) or (air and pollution) and is also equivalent to the search (water or air) and pollution .
boolean operators Include both logical operators and positional operators. Governed by algebraic rules (that is, the precedence of performance of the operations -- as in algebra, for instance, when the operation inside the parentheses is always performed first).
boolean searching Using search techniques which utilize boolean operators and boolean logic
controlled vocabulary Terms used to describe the contents and typology of items in a database are drawn from a specific list or lists. In North American library databases, the Library of Congress Subject Headings frequently provide the necessary controlled vocabulary. Commercial databases often have thesauri and/or indexes provided for the same purpose.
default operator A logical or positional operator that, by default, works on the terms entered in a search unless it is specifically replaced
dirty search A relatively unstructured, poorly planned search that leads to numerous false drops.
false drops Results produced by a search that do not relate to the intent of the search. For example, a search of ira might produce records relating to the Irish Republican Army, the International Reading Association, Individual Retirement Account, and everyone in the database named Ira. False drops can be mitigated by the construction and use of a proper search strategy, and by knowledge of the controlled vocabulary
field (searching) Every record in a database is made up of fields. For example, in library records, the title field contains the title information while the subject field contains the subject information. In a word processing application, users can create fields for names, street addresses, city information, etc. Often records in databases can be sorted or searched based upon field information.
free text searching In the event of no controlled vocabulary or an unknown controlled vocabulary, searching (any) word(s) in (any) field, hoping to match the terms used by the indexers. Free text searching is the dirtiest of dirty searching.
logical operators Generally, and or not xor. and serves as the term of logical conjunction; or serves as the term of logical inclusion; not serves as the term of logical negation; xor includes all items with one search word but not items with both words. In some databases logical operators will be expressed by symbols (¦ for or; & for and; &! for not), the searcher will be required to present the logical operator in upper case (eg OR) in order for it to perform properly, or the database may have a default operator.
masking Replacing a letter or character within a search with a specific character which has meaning for the search engine. For example, in some search engines the character ? would substitute for another character or no character, thus allowing the searcher to return all items that fit either criteria. Thus, searching wom?n would return all items or records with the term women or woman. Sometimes called a wild card
natural language Expressing a search in the same way as a human searcher would express it in speech. For example, searching for the First World War instead of World War, 1914-1918, or querying the search engine by asking -- Tell me about the First World War. In response, the search engine extracts the pertinent phrase and returns items that contain it.
nested terms Terms or phrases which are bound together in a particular order using parentheses (or sometimes quotation marks). Depending on the search engine, the search of a nested term may result in records or items being returned only if the terms searched appear in the particular order expressed within the search. For example, (united nations peacekeepers) would return only those records or items in which the word united was followed by the word nations followed by the word peacekeepers. Related to positional operators.
noise Extra words that are not searchable by the search engine. For example, the, a, an, or any term that is too broad to be useful in the database being searched. Related to stop words.
null search An empty search in which the searcher may set options or restrictions on the search but does not actually enter any terms. Alternatively, a search that cannot be performed because it contains only operators, noise and stop words. For example, in many search engines, to be or not to be is a null search and may even hang the searcher because to and be are stop words and or and not are logical operators.
positional operators Sometimes called proximity operators. Allow the search to stipulate the position of one search term in relation to another. Generally includes: adj near same followed by with. The operator adj between two search terms restricts the items returned by the search to those in which the search terms appear immediately adjacent to each other. The operator near restricts the items returned by the search to those in which the search terms appear in any order but appear with only a specified number of words separating them (eg. community near:2 college). The operator same restricts the items returned to those in which the search terms appear in the same field or group of fields within the items. The operator followed by generally restricts the order of the search terms and requires their immediate adjacency. The operator with generally restricts the items returned to those in which the search terms appear in the same sentence.
proximity operators See: positional operators
relevance searching Some search engines rank the items returned by a search in relevance order based on a combination of determinants such as: the number of words in the item; the number of times the search terms appear in the item; the prominence of the search terms in the item (usually based on the tags used in coding); the parts of speech represented in the search request; and the like.
stem search See: truncation
stop words Words that a search engine has been programmed not to search. May include: have, as, that, was. Related to noise.
truncation Allows a character (the character varies widely from system to system and might be a ?, #, *, :, etc.) to be placed at the beginning or end of a stem, thus instructing the computer to search for the stem string no matter where it occurs in a word. For example, ?electric would produce items containing the word hydroelectric, piezoelectric, and electric, among others, while electric? would produce items containing the words electric, electrical, electricity, etc. In some systems, truncation can be refined by the addition of a number. For example, nation:2 would return only those items containing words with up to two additional characters on the stem word: nation, nations, national, but not nationality. In other systems, the truncation can occur at either end. On the Internet, truncation may occur by default; hence a search on edi might produce medical and edited as well as edi. Related to masking.
wild card See: masking

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Created: 1998/09/11 Last updated: 2011/12/15
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