/*
 * @(#)Expression.java
 *
 * Copyright 2005 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
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 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
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package com.sun.xacml.cond;

import java.io.OutputStream;
import java.net.URI;

import com.sun.xacml.Indenter;

/**
 * This interface represents the expression type in the XACML 2.0 schema.
 * 
 * @since 2.0
 * @author Seth Proctor
 */
public interface Expression {

    /**
     * Returns the type of the expression. This may be the data type of an
     * <code>AttributeValue</code>, the return type of a <code>Function</code>, etc.
     * 
     * @return the attribute type of the referenced expression
     */
    public URI getType();

    /**
     * Returns whether or not this expression returns, or evaluates to a Bag. Note that
     * <code>Evaluatable</code>, which extends this interface, defines <code>evaluatesToBag</code>
     * which is essentially the same function. This method has been deprecated, and
     * <code>returnsBag</code> is now the preferred way to query all <code>Expression</code>s.
     */
    public boolean returnsBag();

    /**
     * Encodes this <code>Expression</code> into its XML representation and writes this encoding to
     * the given <code>OutputStream</code> with no indentation.
     * 
     * @param output
     *            a stream into which the XML-encoded data is written
     */
    public void encode(OutputStream output);

    /**
     * Encodes this <code>Expression</code> into its XML representation and writes this encoding to
     * the given <code>OutputStream</code> with indentation.
     * 
     * @param output
     *            a stream into which the XML-encoded data is written
     * @param indenter
     *            an object that creates indentation strings
     */
    public void encode(OutputStream output, Indenter indenter);

}