org.decision_deck.jmcda.structure.interval.Interval Maven / Gradle / Ivy
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package org.decision_deck.jmcda.structure.interval;
/**
*
* Represents an interval on the set of real numbers, directed if the preference direction is set. This is not
* mandatory. The interval may end at infinity, thus the interval may also represent the whole set of reals.
*
*
* The interval may be discrete in which case a step size s is defined and the minimum m must be non
* infinite. The set of number this represents, supposing the maximum of this interval is infinite, is m+k*s
* with k a positive integer or zero. If the maximum of this interval is defined as a real number M,
* thus if it is not infinite, the set of numbers represented by this interval is m+k*s with k ≥ 0 and
* m+k*s ≤ M.
*
*
* When associated with a criterion, such an interval is typically called a scale and represents the set of numbers an
* evaluation of an alternative over that criterion must belong to. Except indicated otherwise, saying that a scale is
* defined for a given criterion means that it has such an interval associated with it, but not necessarily that the
* preference direction of this interval is defined. Therefore, saying that a scale is defined does not imply that the
* criterion is indeed associated with a directed interval, only that it is associated with an interval.
*
*
* Such an interval is sometimes called ordered interval in the javadoc for legacy reasons.
*
*
* @author Olivier Cailloux
*
*/
public interface Interval {
/**
*
* This interval must have a step size.
*
*
* Retrieves a facade permitting easier usage of this interval when it represents a discrete interval.
*
*
* @return not null.
*/
public DiscreteInterval getAsDiscreteInterval();
/**
*
* The preference direction must be set.
*
*
* Retrieves the maximum value if the preference direction is to maximize, the minimum value if the preference
* direction is to minimize. If the corresponding bound is not set this method returns a positive or negative
* infinity.
*
*
* @return infinity or a real number.
*/
public double getBest();
/**
*
* The preference direction must be set.
*
*
* Useful for computations depending on the preference direction associated with this interval.
*
*
* @return 1 if the preference direction is to maximize, -1 if it is to minimize.
*/
public int getDirectionAsSign();
/**
* Retrieves the maximum value included in this interval, or positive infinity. The returned value is necessarily
* greater than or equal to {@link #getMinimum()}.
*
* @return {@link Double#POSITIVE_INFINITY} or a real number.
*/
public double getMaximum();
/**
* Retrieves the minimum value included in this interval, or negative infinity. The returned value is necessarily
* smaller than or equal to {@link #getMaximum()}.
*
* @return {@link Double#NEGATIVE_INFINITY} or a real number.
*/
public double getMinimum();
/**
* Retrieves the preference direction associated to this interval.
*
* @return null for not set.
*/
public PreferenceDirection getPreferenceDirection();
/**
* Retrieves the step size bound to this interval, or null if no step size is defined. If the step size
* is defined, the minimum of this interval is a real, thus non-infinite, number.
*
* @return null for no step size, or a number greater than zero.
*/
public Double getStepSize();
/**
*
* The preference direction must be set.
*
*
* Retrieves the minimum value if the preference direction is to maximize, the maximum value if the preference
* direction is to minimize. If the corresponding bound is not set this method returns a positive or negative
* infinity.
*
*
* @return infinity or a real number.
*/
public double getWorst();
}