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| <html> |
| <head> |
| <title>Min Number Should Match Specification Format</title> |
| </head> |
| |
| <body> |
| <h1>Min Number Should Match Specification Format</h1> |
| |
| <blockquote> |
| This document explains the format used for specifying the |
| "Min Number Should Match" criteria of the BooleanQuery objects built by the |
| DisMaxRequestHandler. |
| </blockquote> |
| |
| |
| <h2>Explanation of Concept: "Min Number Should Match"</h2> |
| <div> |
| :TODO: |
| </div> |
| |
| |
| <h2>Specification Format</h2> |
| <div> |
| |
| <p>Specification strings may have the following formats...</p> |
| |
| <dl> |
| |
| <dt><code>3</code></dt> |
| <dd>A positive integer, indicating a fixed value regardless of the |
| number of optional clauses. |
| </dd> |
| |
| <dt><code>-2</code></dt> |
| <dd>A negative integer, indicating that the total number of optional clauses, |
| minus this number should be mandatory. |
| </dd> |
| |
| <dt><code>75%</code></dt> |
| <dd>A percentage, indicating that this percent of the total number of |
| optional clauses are necessary. The number computed from the |
| percentage is rounded down and used as the minimum. |
| </dd> |
| |
| <dt><code>-25%</code></dt> |
| <dd>A negative percentage, indicating that this percent of the total |
| number of optional clauses can be missing. The number computed from the |
| percentage is rounded down, before being subtracted from the total |
| to determine the minimum. |
| </dd> |
| |
| <dt><code>3<90%</code></dt> |
| <dd>A positive integer, followed by the less-than symbol, followed |
| by any of the previously mentioned specifiers is a conditional |
| specification. It indicates that if the number of optional clauses is |
| equal to (or less than) the integer, they are all required, but |
| if it's greater than the integer, the specification applies. |
| In this example: if there are 1 to 3 clauses they are all required, |
| but for 4 or more clauses only 90% are required. |
| </dd> |
| |
| <dt><code>2<-25% 9<-3</code></dt> |
| <dd>Multiple conditional specifications can be separated by spaces, |
| each one only being valid for numbers greater than the one before it. |
| In this example: if there are 1 or 2 clauses both are required, |
| if there are 3-9 clauses all but 25% are required, and if there |
| are more than 9 clauses, all but three are required. |
| </dd> |
| </dl> |
| |
| <p> |
| A few important notes... |
| </p> |
| |
| <ul> |
| <li> |
| When dealing with percentages, negative values can be used to get |
| different behavior in edge cases. 75% and -25% mean the same thing |
| when dealing with 4 clauses, but when dealing with 5 clauses 75% means |
| 3 are required, but -25% means 4 are required. |
| </li> |
| <li> |
| If the calculations based on the specification determine that no |
| optional clauses are needed, the usual rules about BooleanQueries |
| still apply at search time (a BooleanQuery containing no required |
| clauses must still match at least one optional clause) |
| </li> |
| <li> |
| No matter what number the calculation arrives at, |
| a value greater than the number of optional clauses, or a value less than |
| 1 will never be used. (ie: no matter how low or how high the result of the |
| calculation result is, the minimum number of required matches will never |
| be lower than 1 or greater than the number of clauses. |
| </li> |
| </ul> |
| |
| |
| </div> |
| </body> </html> |
