BackwardChainer.h

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/*
 * BackwardChainer.h
 *
 * Copyright (C) 2014 Misgana Bayetta
 * Copyright (C) 2015 OpenCog Foundation
 *
 * Author: Misgana Bayetta <misgana.bayetta@gmail.com>  October 2014
 *         William Ma <https://github.com/williampma>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License v3 as
 * published by the Free Software Foundation and including the exceptions
 * at http://opencog.org/wiki/Licenses
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, write to:
 * Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifndef BACKWARDCHAINER_H_
#define BACKWARDCHAINER_H_

#include <opencog/rule-engine/Rule.h>
#include <opencog/rule-engine/UREConfigReader.h>

#include "Target.h"

class BackwardChainerUTest;

namespace opencog
{
    
typedef std::map<Handle, UnorderedHandleSet> VarMultimap;
typedef std::map<Handle, Handle> VarMap;

class BackwardChainer
{
    friend class ::BackwardChainerUTest;

public:
    BackwardChainer(AtomSpace& as, Handle rbs);

    void set_target(Handle init_target);
    UREConfigReader& get_config();
    const UREConfigReader& get_config() const;

    void do_chain();
    void do_step();

    const VarMultimap& get_chaining_result();

private:

    void process_target(Target& target);

    std::vector<Rule> filter_rules(const Target& target);
    Rule select_rule(Target& target, const std::vector<Rule>& rules);

    HandleSeq match_knowledge_base(const Handle& htarget,
                                   Handle htarget_vardecl,
                                   std::vector<VarMap>& vmap);
    HandleSeq ground_premises(const Handle& htarget, const VarMap& vmap,
                              std::vector<VarMap>& vmap_list);
    bool unify(const Handle& hsource, const Handle& hmatch,
               Handle hsource_vardecl, Handle hmatch_vardecl, VarMap& result);

    Handle gen_sub_varlist(const Handle& parent, const Handle& parent_varlist,
                           std::set<Handle> additional_free_varset);

    AtomSpace& _as;
    UREConfigReader _configReader;
    AtomSpace _garbage_superspace;
    Handle _init_target;

    TargetSet _targets_set;

    // XXX any additional link should be reflected
    unordered_set<Type> _logical_link_types = { AND_LINK, OR_LINK, NOT_LINK };
};


} // namespace opencog

#endif /* BACKWARDCHAINER_H_ */