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/**
* Literal
* Copyright 2011 by Michael Peter Christen, mc@yacy.net, Frankfurt am Main, Germany
* First released 18.12.2011 at http://yacy.net
*
* $LastChangedDate: 2011-04-14 00:04:23 +0200 (Do, 14 Apr 2011) $
* $LastChangedRevision: 7653 $
* $LastChangedBy: orbiter $
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program in the file lgpl21.txt
* If not, see <http://www.gnu.org/licenses/>.
*/
package net.yacy.cora.lod;
import java.util.regex.Pattern;
import net.yacy.cora.document.id.MultiProtocolURL;
/**
* A literal is the possible value for a predicate.
* A set of literals is the norm of a predicate.
* Each literal can have an attached explanation which we express
* as a link to the resource that explains the literal.
*/
public interface Literal {
/**
* the terminal is the actual content of the property and also
* the visual representation of the content of a property if the
* literal is assigned to that property.
* @return a string representing the literal
*/
public String getTerminal();
/**
* the subject of a literal is a reference to a resource that
* explains the literal. If an object has attached properties
* from different vocabularies and properties assigned to the
* object have actual literal instances assigned, then the set
* of subjects of these literals explain the object as a co-notation
* to knowledge. Subjects of literals shall therefore be
* knowledge authorities for the predicates where the literal is
* assigned.
* @return an url to a knowledge authority for the literal
*/
public MultiProtocolURL getSubject();
/**
* if a resource is poorly annotated with metadata an it shall
* be automatically annotated, then the terminal of a literal
* may be too weak to discover literals in the resource. An additional
* discovery pattern may help to reduce the set of literals that can
* be discovered automatically. A discovery pattern is then not
* a replacement of the terminal itself, it is an additional pattern
* that must occur also in the resource where also the terminal of
* the literal appears. If the terminal itself is sufficient to discover
* the literal, then the discovery pattern may be a catch-all '.*' pattern.
* @return the discovery pattern to identify the literal in the resource.
*/
public Pattern getDiscoveryPattern();
}
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