01 /* This file is part of the project "Hilbert II" - http://www.qedeq.org
02 *
03 * Copyright 2000-2013, Michael Meyling <mime@qedeq.org>.
04 *
05 * "Hilbert II" is free software; you can redistribute
06 * it and/or modify it under the terms of the GNU General Public
07 * License as published by the Free Software Foundation; either
08 * version 2 of the License, or (at your option) any later version.
09 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 */
15
16 package org.qedeq.kernel.bo.logic.common;
17
18
19 /**
20 * Check if the predicate for identity is already defined.
21 *
22 * @author Michael Meyling
23 */
24 public interface IdentityOperatorExistenceChecker {
25
26 /**
27 * Check if the identity operator is already defined.
28 *
29 * @return Identity operator is already defined.
30 */
31 public boolean identityOperatorExists();
32
33 /**
34 * Get identity operator. This is the operator string of a predicate.
35 *
36 * @return Identity operator. Should be <code>null</code>
37 * if !{@link #identityOperatorExists()}.
38 */
39 public String getIdentityOperator();
40
41 }
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