001/*
002 * JScience - Java(TM) Tools and Libraries for the Advancement of Sciences.
003 * Copyright (C) 2006 - JScience (http://jscience.org/)
004 * All rights reserved.
005 * 
006 * Permission to use, copy, modify, and distribute this software is
007 * freely granted, provided that this notice is preserved.
008 */
009package javax.measure.unit;
010
011import java.util.Set;
012
013/**
014 * <p> This class represents a system of units, it groups units together 
015 *     for historical or cultural reasons. Nothing prevents a unit from 
016 *     belonging to several system of units at the same time
017 *     (for example an imperial system would have many of the units 
018 *     held by {@link NonSI}).</p>
019 *
020 * @author  <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
021 * @version 4.2, August 26, 2007
022 */
023public abstract class SystemOfUnits {
024    
025    /**
026     * Returns a read only view over the units defined in this system.
027     *
028     * @return the collection of units.
029     */
030    public abstract Set<Unit<?>> getUnits();
031
032}