org.apache.lucene.search.similarities

## Class BasicModel

- java.lang.Object
- - org.apache.lucene.search.similarities.BasicModel

- Direct Known Subclasses:
    BasicModelG, BasicModelIF, BasicModelIn, BasicModelIne

      public abstract class BasicModel
      extends Object

  This class acts as the base class for the specific basic model implementations in the DFR framework. Basic models compute the informative content Inf1 = -log2Prob1 .
  See Also:
    `DFRSimilarity`
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `BasicModel()` Sole constructor.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract Explanation` | `explain(BasicStats stats, double tfn, double aeTimes1pTfn)` Returns an explanation for the score.
    `abstract double` | `score(BasicStats stats, double tfn, double aeTimes1pTfn)` Returns the informative content score combined with the after effect, more specifically `informationContentScore * aeTimes1pTfn / (1 + tfn)`.
    `abstract String` | `toString()` Subclasses must override this method to return the code of the basic model formula.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### BasicModel

          public BasicModel()

      Sole constructor. (For invocation by subclass constructors, typically implicit.)

  - ### Method Detail

    - #### score

          public abstract double score(BasicStats stats,
                                       double tfn,
                                       double aeTimes1pTfn)

      Returns the informative content score combined with the after effect, more specifically `informationContentScore * aeTimes1pTfn / (1 + tfn)`. This function must be non-decreasing with `tfn`.

    - #### explain

          public abstract Explanation explain(BasicStats stats,
                                              double tfn,
                                              double aeTimes1pTfn)

      Returns an explanation for the score. Subclasses must override this method.

    - #### toString

          public abstract String toString()

      Subclasses must override this method to return the code of the basic model formula. Refer to the original paper for the list.
      Overrides:
        `toString` in class `Object`

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