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package com.sun.msv.grammar;

/**
 * Visitor interface for Expression and its derived types.
 * 
 * <p>
 * You may want to use ExpressionVisitorXXXX class if you want to
 * return boolean, void, or {@link Expression}.
 * 
 * <p>
 * It is the callee's responsibility to traverse child expression.
 * Expression and its derived classes do not provide any traversal.
 * See {@link ExpressionCloner} for example.
 * 
 * <p>
 * onRef method is called for all subclass of ReferenceExp. So you can safely use this
 * interface to visit AGMs from RELAX grammar.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public interface ExpressionVisitor {
    
    Object onAttribute( AttributeExp exp );
    Object onChoice( ChoiceExp exp );
    Object onElement( ElementExp exp );
    Object onOneOrMore( OneOrMoreExp exp );
    Object onMixed( MixedExp exp );
    Object onList( ListExp exp );
    Object onRef( ReferenceExp exp );
    Object onOther( OtherExp exp );
    Object onEpsilon();
    Object onNullSet();
    Object onAnyString();
    Object onSequence( SequenceExp exp );
    Object onData( DataExp exp );
    Object onValue( ValueExp exp );
    Object onConcur( ConcurExp p );
    Object onInterleave( InterleaveExp p );
}
