001/* Interface representing a dependency between ports.
002
003 Copyright (c) 2003-2013 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
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022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028package ptolemy.actor.util;
029
030///////////////////////////////////////////////////////////////////
031//// Dependency
032
033/**
034 This interface provides a dependency for causality interfaces as described
035 in the paper "Causality Interfaces for Actor Networks" by Ye Zhou and
036 Edward A. Lee, ACM Transactions on Embedded Computing Systems (TECS),
037 April 2008, as available as <a href="http://www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-148.pdf">
038 Technical Report No. UCB/EECS-2006-148</a>,
039 November 16, 2006.
040 <p>
041 A dependency represents a causality relationship between two ports.
042 Implementations of this interface are required to satisfy certain
043 algebraic properties, but as long as these are satisfied, there is
044 considerable freedom.
045
046 @author Edward A. Lee
047 @version $Id$
048 @since Ptolemy II 8.0
049 @Pt.ProposedRating Yellow (eal)
050 @Pt.AcceptedRating Red (eal)
051 */
052public interface Dependency extends Comparable<Dependency> {
053
054    ///////////////////////////////////////////////////////////////////
055    ////                         public methods                    ////
056
057    /** Return a dependency that results from parallel composition of
058     *  this one and the specified one. This is required to be
059     *  associative and commutative. That is, d1.oPlus(d2).oPlus(d3)
060     *  should be equal to d1.oPlus(d2.oPlus(d3)), and
061     *  d1.oPlus(d2) should be equal to d2.oPlus(d1).
062     *  In addition, any implementation should be idempotent,
063     *  meaning that d.oPlus(d) is equal to d.
064     *  @param d The dependency to add.
065     *  @return A dependency whose value is the logical OR of the two dependency
066     *   values.
067     *  @exception ClassCastException if d is not a BooleanDependency.
068     */
069    public Dependency oPlus(Dependency d);
070
071    /** Return the dependency that when added to any other
072     *  dependency using oPlus() yields the other dependency.
073     *  @return The additive identity.
074     */
075    public Dependency oPlusIdentity();
076
077    /** Return a dependency that results from serial composition of
078     *  this one and the specified one. This is required to be
079     *  associative, but not necessarily commutative.
080     *  That is, d1.oTimes(d2).oTimes(d3)
081     *  should be equal to d1.oTimes(d2.oTimes(d3)).
082     *  Moreover, it should be distributive over oPlus.
083     *  That is, d1.oTimes(d2.oPlus(d3)) should be equal to
084     *  (d1.oTimes(d2)).oPlus(d1.oTimes(d3)).
085     *  @param d The dependency to multiply.
086     *  @return A dependency whose value is the logical AND of the value of
087     *   this one and the specified one.
088     *  @exception ClassCastException if d is not a BooleanDependency.
089     */
090    public Dependency oTimes(Dependency d);
091
092    /** Return the dependency that when multiplied by any other
093     *  dependency using oTimes() yields the other dependency.
094     *  @return The multiplicative identity.
095     */
096    public Dependency oTimesIdentity();
097
098    ///////////////////////////////////////////////////////////////////
099    ////                         public fields                     ////
100
101    /** Return value of compareTo() if this is equal to the argument. */
102    public static final int EQUALS = 0;
103
104    /** Return value of compareTo() if this is greater than the argument. */
105    public static final int GREATER_THAN = 1;
106
107    /** Return value of compareTo() if this is incomparable to the argument. */
108    public static final int INCOMPARABLE = 2;
109
110    /** Return value of compareTo() if this is less than the argument. */
111    public static final int LESS_THAN = -1;
112}