01: package org.ofbiz.rules.engine;
02:
03: /**
04: * <p><b>Title:</b> Axiom
05: * <p><b>Description:</b> None
06: * <p>Copyright (c) 1999 Steven J. Metsker.
07: * <p>Copyright (c) 2001 The Open For Business Project - www.ofbiz.org
08: *
09: * <p>Permission is hereby granted, free of charge, to any person obtaining a
10: * copy of this software and associated documentation files (the "Software"),
11: * to deal in the Software without restriction, including without limitation
12: * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13: * and/or sell copies of the Software, and to permit persons to whom the
14: * Software is furnished to do so, subject to the following conditions:
15: *
16: * <p>The above copyright notice and this permission notice shall be included
17: * in all copies or substantial portions of the Software.
18: *
19: * <p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20: * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
21: * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
22: * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
23: * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT
24: * OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
25: * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
26: *
27: * <br>
28: * <p>In practice, an Axiom is either a fact or a rule, the two
29: * types of objects that can appear in a program. More
30: * precisely, an Axiom has a head structure with which a
31: * consulting structure can unify, and an Axiom can produce
32: * a ProvableAxiom.
33: * <p>
34: * Facts are simply true, and return themselves as
35: * DynamicAxioms. To prove itself, a Rule needs to
36: * create a DynamicAxiom that can attempt to prove
37: * itself against an axiom source.
38: *
39: * @author Steven J. Metsker
40: * @version 1.0
41: */
42: public interface Axiom {
43:
44: /**
45: * Return an axiom that a consulting structure can use
46: * to prove itself.
47: *
48: * @return an axiom that a consulting structure can use
49: * to prove itself.
50: */
51: DynamicAxiom dynamicAxiom(AxiomSource as);
52:
53: /**
54: * Return the first structure of this axiom.
55: *
56: * @return the first structure of this axiom
57: */
58: Structure head();
59: }
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