/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (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.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 */

#include "nsIRDFDataSource.idl"

interface nsISimpleEnumerator;

/**
 * An nsIRDFCompositeDataSource composes individual data sources, providing
 * the illusion of a single, coherent RDF graph.
 */
[scriptable, uuid(96343820-307C-11D2-BC15-00805F912FE7)]
interface nsIRDFCompositeDataSource : nsIRDFDataSource {

    /**
     *
     * Set this value to <code>true</code> if the composite datasource
     * may contains at least one datasource that has <em>negative</em>
     * assertions. (This is the default.)
     *
     * Set this value to <code>false</code> if none of the datasources
     * being composed contains a negative assertion. This allows the
     * composite datasource to perform some query optimizations.
     *
     * By default, this value is <code>true</true>.
     */
    attribute boolean	allowNegativeAssertions;

    /**
     * Set to <code>true</code> if the composite datasource should
     * take care to coalesce duplicate arcs when returning values from
     * queries. (This is the default.)
     *
     * Set to <code>false</code> if the composite datasource shouldn't
     * bother to check for duplicates. This allows the composite
     * datasource to more efficiently answer queries.
     *
     * By default, this value is <code>true</code>.
     */
    attribute boolean	coalesceDuplicateArcs;

    /**
     * Add a datasource the the composite data source.
     * @param aDataSource the datasource to add to composite
     */
    void AddDataSource(in nsIRDFDataSource aDataSource);

    /**
     * Remove a datasource from the composite data source.
     * @param aDataSource the datasource to remove from the composite
     */
    void RemoveDataSource(in nsIRDFDataSource aDataSource);

    /**
     * Retrieve the datasources in the composite data source.
     * @return an nsISimpleEnumerator that will enumerate each
     * of the datasources in the composite
     */
    nsISimpleEnumerator GetDataSources();
};

%{C++
extern nsresult
NS_NewRDFCompositeDataSource(nsIRDFCompositeDataSource** result);
%}