001 /*
002 // $Id: //open/mondrian/src/main/mondrian/olap/type/Type.java#7 $
003 // This software is subject to the terms of the Common Public License
004 // Agreement, available at the following URL:
005 // http://www.opensource.org/licenses/cpl.html.
006 // Copyright (C) 2005-2008 Julian Hyde
007 // All Rights Reserved.
008 // You must accept the terms of that agreement to use this software.
009 */
010 package mondrian.olap.type;
011
012 import mondrian.olap.Dimension;
013 import mondrian.olap.Hierarchy;
014 import mondrian.olap.Level;
015
016 /**
017 * Type of an MDX expression.
018 *
019 * @author jhyde
020 * @since Feb 17, 2005
021 * @version $Id: //open/mondrian/src/main/mondrian/olap/type/Type.java#7 $
022 */
023 public interface Type {
024 /**
025 * Returns whether this type contains a given dimension.<p/>
026 *
027 * For example:
028 * <ul>
029 * <li><code>DimensionType([Gender])</code> uses only the
030 * <code>[Gender]</code> dimension.</li>
031 * <li><code>TupleType(MemberType([Gender]), MemberType([Store]))</code>
032 * uses <code>[Gender]</code> and <code>[Store]</code>
033 * dimensions.</li>
034 * </ul><p/>
035 *
036 * The <code>definitely</code> parameter comes into play when the
037 * dimensional information is incomplete. For example, when applied to
038 * <code>TupleType(MemberType(null), MemberType([Store]))</code>,
039 * <code>usesDimension([Gender], false)</code> returns true because it
040 * is possible that the expression returns a member of the
041 * <code>[Gender]</code> dimension; but
042 * <code>usesDimension([Gender], true)</code> returns true because it
043 * is possible that the expression returns a member of the
044 * <code>[Gender]</code> dimension.
045 *
046 * @param dimension Dimension
047 * @param definitely If true, returns true only if this type definitely
048 * uses the dimension
049 *
050 * @return whether this Type uses the given Dimension
051 */
052 boolean usesDimension(Dimension dimension, boolean definitely);
053
054 /**
055 * Returns the Dimension of this Type, or null if not known.
056 * If not applicable, throws.
057 *
058 * @return the Dimension of this Type, or null if not known.
059 */
060 Dimension getDimension();
061
062 /**
063 * Returns the Hierarchy of this Type, or null if not known.
064 * If not applicable, throws.
065 *
066 * @return the Hierarchy of this type, or null if not known
067 */
068 Hierarchy getHierarchy();
069
070 /**
071 * Returns the Level of this Type, or null if not known.
072 * If not applicable, throws.
073 *
074 * @return the Level of this Type
075 */
076 Level getLevel();
077
078 /**
079 * Returns a Type which is more general than this and the given Type.
080 * The type returned is broad enough to hold any value of either type,
081 * but no broader. If there is no such type, returns null.
082 *
083 * <p>Some examples:<ul>
084 * <li>The common type for StringType and NumericType is ScalarType.
085 * <li>The common type for NumericType and DecimalType(4, 2) is
086 * NumericType.
087 * <li>DimensionType and NumericType have no common type.
088 * </ul></p>
089 *
090 * <p>If <code>conversionCount</code> is not null, implicit conversions
091 * such as HierarchyType to DimensionType are considered; the parameter
092 * is incremented by the number of conversions performed.
093 *
094 * <p>Some examples:<ul>
095 * <li>The common type for HierarchyType(hierarchy=Time.Weekly)
096 * and LevelType(dimension=Time), if conversions are allowed, is
097 * HierarchyType(dimension=Time).
098 * </ul>
099 *
100 * <p>One use of common types is to determine the types of the arguments
101 * to the <code>Iif</code> function. For example, the call
102 *
103 * <blockquote><code>Iif(1 > 2, [Measures].[Unit Sales], 5)</code></blockquote>
104 *
105 * has type ScalarType, because DecimalType(-1, 0) is a subtype of
106 * ScalarType, and MeasureType can be converted implicitly to ScalarType.
107 *
108 * @param type Type
109 *
110 * @param conversionCount Number of conversions; output parameter that is
111 * incremented each time a conversion is performed; if null, conversions
112 * are not considered
113 *
114 * @return More general type
115 */
116 Type computeCommonType(Type type, int[] conversionCount);
117 }
118
119 // End Type.java