*
                 * QUESTION: getProperty or getPropertyDirect
                 */
                Object value = getProperty((String) key);
                if (value instanceof String)
                {
                    c.addPropertyDirect(newKey, interpolate((String) value));
                }
                else
                {
                    c.addProperty(newKey, value);
                }
            }
        }

        if (validSubset)
        {
            return c;
        }
        else
        {
            return null;
        }
    }

    /**
     * Check if the configuration is empty
     *
     * @return <code>true</code> if Configuration is empty,
     * <code>false</code> otherwise.
     */
    public abstract boolean isEmpty();

    /**
     * check if the configuration contains the key
     *
     * @param key the configuration key
     *
     * @return <code>true</code> if Configuration contain given key,
     * <code>false</code> otherwise.
     */
    public abstract boolean containsKey(String key);

    /**
     * Set a property, this will replace any previously
     * set values. Set values is implicitly a call
     * to clearProperty(key), addProperty(key,value).
     *
     * @param key the configuration key
     * @param value the property value
     */
    public void setProperty(String key, Object value)
    {
        clearProperty(key);
        addProperty(key, value); // QUESTION: or addPropertyDirect?
    }

    /**
     * Clear a property in the configuration.
     *
     * @param key the key to remove along with corresponding value.
     */
    public  abstract void clearProperty(String key);

    /**
     * Get the list of the keys contained in the configuration
     * repository.
     *
     * @return An Iterator.
     */
    public abstract Iterator getKeys();

    /**
     * Get the list of the keys contained in the configuration
     * repository that match the specified prefix.
     *
     * @param prefix The prefix to test against.
     *
     * @return An Iterator of keys that match the prefix.
     */
    public Iterator getKeys(String prefix)
    {
        Iterator keys = getKeys();
        ArrayList matchingKeys = new ArrayList();

        while (keys.hasNext())
        {
            Object key = keys.next();

            if (key instanceof String && ((String) key).startsWith(prefix))
            {
                matchingKeys.add(key);
            }
        }
        return matchingKeys.iterator();
    }

    /**
     * Get a list of properties associated with the given
     * configuration key.
     *
     * @param key The configuration key.
     *
     * @return The associated properties if key is found.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a String/Vector.
     * @throws IllegalArgumentException if one of the tokens is
     * malformed (does not contain an equals sign).
     *
     * @see #getProperties(String, Properties)
     */
    public Properties getProperties(String key)
    {
        return getProperties(key, null);
    }

    /**
     * Get a list of properties associated with the given
     * configuration key.
     *
     * @param key The configuration key.
     * @param defaults Any default values for the returned
     * <code>Properties</code> object.  Ignored if <code>null</code>.
     *
     * @return The associated properties if key is found.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a String/Vector of Strings.
     * @throws IllegalArgumentException if one of the tokens is
     * malformed (does not contain an equals sign).
     */
    public Properties getProperties(String key, Properties defaults)
    {
        /*
         * Grab an array of the tokens for this key.
         */
        String[] tokens = getStringArray(key);

        /*
         * Each token is of the form 'key=value'.
         */
        Properties props =
            (defaults == null ? new Properties() : new Properties(defaults));
        for (int i = 0; i < tokens.length; i++)
        {
            String token = tokens[i];
            int equalSign = token.indexOf('=');
            if (equalSign > 0)
            {
                String pkey = token.substring(0, equalSign).trim();
                String pvalue = token.substring(equalSign + 1).trim();
                props.put(pkey, pvalue);
            }
            else if (tokens.length == 1 && "".equals(token))
            {
                // Semantically equivalent to an empty Properties
                // object.
                break;
            }
            else
            {
                throw new IllegalArgumentException(
                    '\'' + token + "' does not contain an equals sign");
            }
        }
        return props;
    }

    /**
     *  Gets a property from the configuration.
     *
     *  @param key property to retrieve
     *  @return value as object. Will return user value if exists,
     *          if not then default value if exists, otherwise null
     */
    public Object getProperty(String key)
    {
        // first, try to get from the 'user value' store
        Object o = getPropertyDirect(key);

        if (o == null)
        {
            // if there isn't a value there, get it from the defaults if we have
            // them
            if (defaults != null)
            {
                o = defaults.getProperty(key);
            }
        }

        //
        // We must never give a Container Object out. So if the
        // Return Value is a Container, we fix it up to be a
        // Vector
        //
        if (o instanceof Container)
        {
            o = ((Container) o).asVector();
        }
        return o;
   }

    /**
     * Get a boolean associated with the given configuration key.
     *
     * @param key The configuration key.
     *
     * @return The associated boolean.
     *
     * @throws NoSuchElementException is thrown if the key doesn't
     * map to an existing object.
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Boolean.
     */
    public boolean getBoolean(String key)
    {
        Boolean b = getBoolean(key, (Boolean) null);
        if (b != null)
        {
            return b.booleanValue();
        }
        else
        {
            throw new NoSuchElementException(
                '\'' + key + "' doesn't map to an existing object");
        }
    }

    /**
     * Get a boolean associated with the given configuration key.
     *
     * @param key The configuration key.
     * @param defaultValue The default value.
     *
     * @return The associated boolean.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Boolean.
     */
    public boolean getBoolean(String key, boolean defaultValue)
    {
        return getBoolean(key, new Boolean(defaultValue)).booleanValue();
    }

    /**
     * Get a boolean associated with the given configuration key.
     *
     * @param key The configuration key.
     * @param defaultValue The default value.
     *
     * @return The associated boolean if key is found and has valid
     * format, default value otherwise.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Boolean.
     */
    public Boolean getBoolean(String key, Boolean defaultValue)
    {
        Object value = resolveContainerStore(key);

        if (value instanceof Boolean)
        {
            return (Boolean) value;
        }
        else if (value instanceof String)
        {
            return testBoolean((String) value);
        }
        else if (value == null)
        {
            if (defaults != null)
            {
                return defaults.getBoolean(key, defaultValue);
            }
            else
            {
                log.warn("Use Boolean default value for key '" + key + "' (" + defaultValue + ")");
                return defaultValue;
            }
        }
        else
        {
            throw new ClassCastException(
                '\'' + key + "' doesn't map to a Boolean object");
        }
    }

    /**
     * Get a byte associated with the given configuration key.
     *
     * @param key The configuration key.
     *
     * @return The associated byte.
     *
     * @throws NoSuchElementException is thrown if the key doesn't
     * map to an existing object.
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Byte.
     * @throws NumberFormatException is thrown if the value mapped
     * by the key has not a valid number format.
     */
    public byte getByte(String key)
    {
        Byte b = getByte(key, null);
        if (b != null)
        {
            return b.byteValue();
        }
        else
        {
            throw new NoSuchElementException(
                '\'' + key + " doesn't map to an existing object");
        }
    }

    /**
     * Get a byte associated with the given configuration key.
     *
     * @param key The configuration key.
     * @param defaultValue The default value.
     *
     * @return The associated byte.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Byte.
     * @throws NumberFormatException is thrown if the value mapped
     * by the key has not a valid number format.
     */
    public byte getByte(String key, byte defaultValue)
    {
        return getByte(key, new Byte(defaultValue)).byteValue();
    }

    /**
     * Get a byte associated with the given configuration key.
     *
     * @param key The configuration key.
     * @param defaultValue The default value.
     *
     * @return The associated byte if key is found and has valid format, default
     *         value otherwise.
     *
     * @throws ClassCastException is thrown if the key maps to an object that
     *            is not a Byte.
     * @throws NumberFormatException is thrown if the value mapped by the key
     *            has not a valid number format.
     */
    public Byte getByte(String key, Byte defaultValue)
    {
        Object value = resolveContainerStore(key);

        if (value instanceof Byte)
        {
            return (Byte) value;
        }
        else if (value instanceof String)
        {
            Byte b = new Byte((String) value);
            return b;
        }
        else if (value == null)
        {
            if (defaults != null)
            {
                return defaults.getByte(key, defaultValue);
            }
            else
            {
                log.warn("Use Byte default value for key '" + key + "' (" + defaultValue + ")");
                return defaultValue;
            }
        }
        else
        {
            throw new ClassCastException(
                '\'' + key + "' doesn't map to a Byte object");
        }
    }

    /**
     * Get a double associated with the given configuration key.
     *
     * @param key The configuration key.
     *
     * @return The associated double.
     *
     * @throws NoSuchElementException is thrown if the key doesn't
     * map to an existing object.
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a Double.
     * @throws NumberFormatException is thrown if the value mapped
     * by the key has not a valid number format.
     */
    public double getDouble(String key)
    {
        Double d = getDouble(key, null);
        if (d != null)
        {