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 * Licensed to the Apache Software Foundation (ASF) under one
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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.rdf.model;

import java.util.Iterator;

import org.apache.jena.reasoner.* ;

/**
 * An extension to the normal Model interface that supports access to any
 * underlying inference capability. 
 * <p>In Jena the primary use of inference is
 * to generate additional entailments from a set of RDF data. These entailments
 * just appear as additional RDF data in the inferred model and are accessed
 * through the normal API. For example, if an inference engine can determine
 * the class of a resource "foo" is "fooClass" then all Model API calls such
 * as listStatements and getProperty should act as if the triple:
 * <pre>
 * foo rdf:type fooClass .
 * </pre>
 * were in the data. </p>
 * 
 * <p>A few reasoner services cannot be made directly available in this way
 * and the InfGraph extension gives access to these - specifically access to 
 * validation/consistency checking, derivation traces and find-with-posits.</p>
 * 
 * <p>Note that this interface, and especially the interface onto ValidityReports
 * and Derivations are not yet stable.</p>
 */
public interface InfModel extends Model {

    /**
     * Return the raw RDF model being processed (i.e. the argument
     * to the Reasonder.bind call that created this InfModel).
     */
    public Model getRawModel();
    
    /**
     * Return the Reasoner which is being used to answer queries to this graph.
     */
    public Reasoner getReasoner();

    /**
     * Cause the inference model  to reconsult the underlying data to take
     * into account changes. Normally changes are made through the InfModel's add and
     * remove calls are will be handled appropriately. However, in some cases changes
     * are made "behind the InfModels's back" and this forces a full reconsult of
     * the changed data. 
     */
    public void rebind();
    
    /**
     * Perform any initial processing and caching. This call is optional. Most
     * engines either have negligable set up work or will perform an implicit
     * "prepare" if necessary. The call is provided for those occasions where
     * substantial preparation work is possible (e.g. running a forward chaining
     * rule system) and where an application might wish greater control over when
     * this prepration is done rather than just leaving to be done at first query time.
     */
    public void prepare();
    
    /**
     * Reset any internal caches. Some systems, such as the tabled backchainer, 
     * retain information after each query. A reset will wipe this information preventing
     * unbounded memory use at the expense of more expensive future queries. A reset
     * does not cause the raw data to be reconsulted and so is less expensive than a rebind.
     */
    public void reset();
    
    /**
     * Test the consistency of the underlying data. This normally tests
     * the validity of the bound instance data against the bound
     * schema data. 
     * <p>Logically inconsistent models will be indicated by a ValidityReport which
     * reports isValid() as false. Additional non.error problems, such as uninstantiatable classes,
     * may be reported as warnings.
     * @return a ValidityReport structure
     */
    public ValidityReport validate();    
    
    /** Find all the statements matching a pattern.
     * <p>Return an iterator over all the statements in a model
     *  that match a pattern.  The statements selected are those
     *  whose subject matches the <code>subject</code> argument,
     *  whose predicate matches the <code>predicate</code> argument
     *  and whose object matchesthe <code>object</code> argument.
     *  If an argument is <code>null</code> it matches anything.</p>
     * <p>
     * The s/p/o terms may refer to resources which are temporarily defined in the "posit" model.
     * This allows one, for example, to query what resources are of type CE where CE is a
     * class expression rather than a named class - put CE in the posit arg.</p>
     * 
     * @return an iterator over the subjects
     * @param subject   The subject sought
     * @param predicate The predicate sought
     * @param object    The value sought
     */ 
    public StmtIterator listStatements( Resource subject, Property predicate, RDFNode object, Model posit );
    
    /**
     * Switch on/off drivation logging. If this is switched on then every time an inference
     * is a made that fact is recorded and the resulting record can be access through a later
     * getDerivation call. This may consume a lot of space!
     */
    public void setDerivationLogging(boolean logOn);
   
    /**
     * Return the derivation of the given statement (which should be the result of
     * some previous list operation).
     * Not all reasoneers will support derivations.
     * @return an iterator over Derivation records or null if there is no derivation information
     * available for this triple.
     * @see org.apache.jena.reasoner.Derivation Derviation
     */
    public Iterator<Derivation> getDerivation(Statement statement);    
    
    /**
     * Returns a derivations model. The rule reasoners typically create a 
     * graph containing those triples added to the base graph due to rule firings.
     * In some applications it can useful to be able to access those deductions
     * directly, without seeing the raw data which triggered them. In particular,
     * this allows the forward rules to be used as if they were rewrite transformation
     * rules.
     * @return the deductions model, if relevant for this class of inference
     * engine or null if not.
     */
    public Model getDeductionsModel(); 

}
