1 /* This file is part of the project "Hilbert II" - http://www.qedeq.org" target="alexandria_uri">http://www.qedeq.org
2 *
3 * Copyright 2000-2014, Michael Meyling <mime@qedeq.org>.
4 *
5 * "Hilbert II" is free software; you can redistribute
6 * it and/or modify it under the terms of the GNU General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
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.se.base.module;
17
18 import org.qedeq.kernel.se.base.list.Element;
19
20
21 /**
22 * Rule of existential generalization.
23 * <pre>
24 * A(x) -> B
25 * -----------------------
26 * exists x A(x) -> B
27 * </pre>
28 *
29 * @author Michael Meyling
30 */
31 public interface Existential extends Reason {
32
33 /**
34 * Get this reason.
35 *
36 * @return This reason.
37 */
38 public Existential getExistential();
39
40 /**
41 * Get reference to formula. Usually this a formula of type A(x) -> B
42 *
43 * @return Reference to previously proved formula.
44 */
45 public String getReference();
46
47
48 /**
49 * Get free subject variable we want to quantify over.
50 *
51 * @return Free subject variable.
52 */
53 public Element getSubjectVariable();
54
55 }