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Lextek Language Identifier
P_AND
Name
P_AND
Synopsis
Returns records where all the terms or subqueries are present.
Arguments
P-value (bias for ranking)
List of terms and subqueriesRanking Scheme
Ranks using the p-norm method. Conceptually you can consider each term a unique direction in n-space (where n is the number of terms). Each term's weight represents the distance in that direction. The p-value (p in the above formula) represents how much the final calculation is like the maximum weight or like the total distance of all vectors in n-space. For p = 2 the p-norm is identical to a vector space model. As p approaches infinity the returned weight becomes equal to the largest weight among the terms.
Picking an appropriate p-value can be tricky and often is the result of experimentation. A simplified way of thinking about the calculation is that it varies between a kind of average weight to the maximum weight. Generally a p-value of 2.5 or 3 is effective.
The p-norm weighting method is one of the most efficient methods available, especially if you've been careful in choosing how you weight your terms.
Note that the p-norm calculation for an AND is slightly different than those for ORs.
Comments
P_AND requires that all the listed terms and subqueries be present in a record for any hit in that record to be returned.
See Also
