/*
 * Copyright  2003-2004 The Apache Software Foundation.
 *
 *  Licensed 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.xml.security.encryption;

import org.w3c.dom.Attr;


/**
 * <code>CipherReference</code> identifies a source which, when processed,
 * yields the encrypted octet sequence.
 * <p>
 * The actual value is obtained as follows. The <code>CipherReference URI</code>
 * contains an identifier that is dereferenced. Should the
 * <code>CipherReference</code> element contain an OPTIONAL sequence of
 * Transforms, the data resulting from dereferencing the <code>URI</code> is
 * transformed as specified so as to yield the intended cipher value. For
 * example, if the value is base64 encoded within an XML document; the
 * transforms could specify an XPath expression followed by a base64 decoding so
 * as to extract the octets.
 * <p>
 * The syntax of the <code>URI</code> and Transforms is similar to that of
 * [XML-DSIG]. However, there is a difference between signature and encryption
 * processing. In [XML-DSIG] both generation and validation processing start
 * with the same source data and perform that transform in the same order. In
 * encryption, the decryptor has only the cipher data and the specified
 * transforms are enumerated for the decryptor, in the order necessary to obtain
 * the octets. Consequently, because it has different semantics Transforms is in
 * the &xenc; namespace.
 * <p>
 * The schema definition is as follows:
 * <xmp>
 * <element name='CipherReference' type='xenc:CipherReferenceType'/>
 * <complexType name='CipherReferenceType'>
 *     <sequence>
 *         <element name='Transforms' type='xenc:TransformsType' minOccurs='0'/>
 *     </sequence>
 *     <attribute name='URI' type='anyURI' use='required'/>
 * </complexType>
 * </xmp>
 *
 * @author Axl Mattheus
 */
public interface CipherReference {
    /**
     * Returns an <code>URI</code> that contains an identifier that should be
     * dereferenced.
     * @return
     */
    String getURI();

	/**
	 * Gets the URI as an Attribute node.  Used to meld the CipherREference
	 * with the XMLSignature ResourceResolvers
     * @return
	 */
	public Attr getURIAsAttr();

    /**
     * Returns the <code>Transforms</code> that specifies how to transform the
     * <code>URI</code> to yield the appropiate cipher value.
     *
     * @return the transform that specifies how to transform the reference to
     *   yield the intended cipher value.
     */
    Transforms getTransforms();

    /**
     * Sets the <code>Transforms</code> that specifies how to transform the
     * <code>URI</code> to yield the appropiate cipher value.
     *
     * @param transforms the set of <code>Transforms</code> that specifies how
     *   to transform the reference to yield the intended cipher value.
     */
    void setTransforms(Transforms transforms);
}