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 * The Apache Software License, Version 1.1
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 2002, International
 * Business Machines Corporation., http://www.ibm.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xpath.expression;

import org.apache.xpath.XPath20Exception;


/**
 * Represents a step. 
 * <quote>A step generates a sequence of items and then filters the sequence 
 * by zero or more predicates.</quote>
 * @see <a href="http://www.w3.org/TR/xpath20/#id-axis-steps">XPath 2.0
 *      specification</a>
 */
public interface StepExpr extends Expr
{
    /**
     * Full name of axis. This array is kept in synchronization with axis
     * constants.
     */
    static final String[] FULL_AXIS_NAME = 
                                           {
                                               "", "child", "descendant",
                                               "parent", "attribute", "self",
                                               "descendant-or-self", "ancestor",
                                               "following-sibling",
                                               "preceding-sibling", "following",
                                               "preceding", "namespace",
                                               "ancestor-or-self"
                                           };

    /**
     * The step axis is child
     */
    static final short AXIS_CHILD = 1;

    /**
     * The step axis is descendant
     */
    static final short AXIS_DESCENDANT = 2;

    /**
     * The step axis is parent
     */
    static final short AXIS_PARENT = 3;

    /**
     * The step axis is attribute
     */
    static final short AXIS_ATTRIBUTE = 4;

    /**
     * The step axis is self
     */
    static final short AXIS_SELF = 5;

    /**
     * The step axis is descendant or self
     */
    static final short AXIS_DESCENDANT_OR_SELF = 6;

    /**
     * The step axis is ancestor
     */
    static final short AXIS_ANCESTOR = 7;

    /**
     * The step axis is following sibling
     */
    static final short AXIS_FOLLOWING_SIBLING = 8;

    /**
     * The step axis is preceding sibling
     */
    static final short AXIS_PRECEDING_SIBLING = 9;

    /**
     * The step axis is following
     */
    static final short AXIS_FOLLOWING = 10;

    /**
     * The step axis is preceding
     */
    static final short AXIS_PRECEDING = 11;

    /**
     * The step axis is namespace
     */
    static final short AXIS_NAMESPACE = 12;

    /**
     * The step axis is ancestor or self
     */
    static final short AXIS_ANCESTOR_OR_SELF = 13;

    /**
     * Tells whether or not this step is a foward axis step
     * @return boolean
     */
    boolean isForwardStep();

    /**
     * Tells whether or not this step is a reversed axis step
     * @return boolean
     */
    boolean isReversedStep();

    /**
     * Tells whether or not this step is a filter step.
     * @return boolean
     */
    boolean isPrimaryExpr();

    /**
     * Gets the type of step axis
     *
     * @return short The axis type corresponding to one of the constants defined above.
     * @throws XPath20Exception whenever the step is neither a forward step nor a reverse
     *         step.
     */
    short getAxisType() throws XPath20Exception;

    /**
     * Sets the type of the step axis
     * @param newType The new axis type
     * @throws XPath20Exception whenever the step is not a forward or reverse
     *         step.
     */
    void setAxisType(short newType) throws XPath20Exception;

    /**
     * Gets the name of the step axis
     *
     * @return String Full name of the step axis
     * @throws XPath20Exception whenever the step is not a forward or reverse
     *         step.
     */
    String getAxisName() throws XPath20Exception;

    /**
     * Gets the node test 
     *
     * @return NodeTest
     * @throws XPath20Exception whenever the step is not a forward or reverse
     *          step.
     */
    NodeTest getNodeTest() throws XPath20Exception;
    
	/**
	 * Sets the node test 
	 *
	 * @param NodeTest
	 * @throws XPath20Exception whenever the step is not a forward or reverse
	 *          step.
	 */
	void setNodeTest(NodeTest test) throws XPath20Exception;


    /**
     * Gets the step as a primary expression. 
     *
     * @return Expr The primary expression 
     */
    Expr getPrimaryExpr() throws XPath20Exception;

    /**
     * Gets the predicate expression at the specified position
     * @param i index of the predicate to return
     * @return The predicate at the ith position
     * @throws java.lang.ArrayIndexOutOfBoundsException
     */
    Expr getPredicateAt(int i);

    /**
     * Gets the number of predicate
     *
     * @return The number of predicates
     */
    int getPredicateCount();

    /**
     * Append the specified predicate
     * @param predicate The predicate to append
     */
    void appendPredicate(Expr predicate);

    /**
     * Remove the specified predicate
     */
    void removePredicate(Expr predicate);
}