Bug 126839 [DataBinding] IObservable refactoring
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/provisional/databinding/IUpdatableFunction.java
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package org.eclipse.jface.internal.provisional.databinding;
/**
 * Represents a function whose value may change over time. The function
 * will fire a CHANGE event whenever the value of the function changes
 * for some domain object. The getNewValue() in the ChangeEvent will be
 * a Collection of domain objects for which the function value has changed.
 * 
 * <p>
 * A function is only required to report CHANGE events for values in its 
 * domain that it has previously been asked to evaluate. That is, an