Class FunctionalDependencyHelper


  • public class FunctionalDependencyHelper
    extends java.lang.Object
    Helper utility class for functional dependency analysis. Throughout this class attribute sets are represented as generic sets and functional dependencies as maps from attribute set (generic sets) to attribute set (generic sets)
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static <A> java.util.Set<A> closureOf​(java.util.Collection<A> attributes, java.util.Map<java.util.Set<A>,​java.util.Set<A>> dependencies)
      Get the closure of the specified attribute set relative to the specified functional dependencies.
      static <A> void includeDependencies​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> accumulator, java.util.Map<java.util.Set<A>,​java.util.Set<A>> additionalDependencies)
      Adds all given dependencies to a mutable accumulator.
      static <A> void includeDependency​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> accumulator, java.util.Set<A> left, java.util.Set<A> right)
      Adds a given dependency to a mutable accumulator.
      static <A> boolean isTrivial​(java.util.Set<A> left, java.util.Set<A> right)  
      static <A> java.util.Map<java.util.Set<A>,​java.util.Set<A>> projectDependencies​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> originalDependencies, java.util.Set<A> targetAttributes)
      Returns the dependency set over attributes in targetAttributes that are implied by a given source dependency set.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • closureOf

        public static <A> java.util.Set<A> closureOf​(java.util.Collection<A> attributes,
                                                     java.util.Map<java.util.Set<A>,​java.util.Set<A>> dependencies)
        Get the closure of the specified attribute set relative to the specified functional dependencies.
        Parameters:
        attributes - The attributes to get the closure of.
        dependencies - The functional dependencies of which the closure operation is relative to.
        Returns:
        The closure of the specified attribute set relative to the specified functional dependencies.
      • isTrivial

        public static <A> boolean isTrivial​(java.util.Set<A> left,
                                            java.util.Set<A> right)
        Returns:
        true if the dependency from the left set to the right set is trivial
        Since:
        1.5
      • projectDependencies

        public static <A> java.util.Map<java.util.Set<A>,​java.util.Set<A>> projectDependencies​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> originalDependencies,
                                                                                                     java.util.Set<A> targetAttributes)
        Returns the dependency set over attributes in targetAttributes that are implied by a given source dependency set.

        Note: exponential in the size of the target attribute set.

        Note: minimality of the returned dependency set is currently not guaranteed.

        Parameters:
        originalDependencies - all dependencies that are known to hold on a wider set of attributes
        targetAttributes - the set of attributes we are interested in
        Since:
        1.5
      • includeDependency

        public static <A> void includeDependency​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> accumulator,
                                                 java.util.Set<A> left,
                                                 java.util.Set<A> right)
        Adds a given dependency to a mutable accumulator.
        Since:
        1.5
      • includeDependencies

        public static <A> void includeDependencies​(java.util.Map<java.util.Set<A>,​java.util.Set<A>> accumulator,
                                                   java.util.Map<java.util.Set<A>,​java.util.Set<A>> additionalDependencies)
        Adds all given dependencies to a mutable accumulator.
        Since:
        1.5