Hi Doug:

please can you provide me with an answer for 4.1 below.

How would you stop a traversal in DJ?

-- Karl
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Question 4:
=====================
30 points

The following is from 
XML for Java Compatibility API 2.0.15.
http://falconet.inria.fr/~java/classes/xml4j/TXapiDocs/
It is NOT expected that you have seen those pages.

I show you pieces of the documentation and ask
you to interpret it based on your knowledge of traversal/visitor
programming.

Consider the following example of XML4J (XML for Java) code:

----
PrintWriter printWriter = new PrintWriter();
Visitor htmlPrintVisitor = new HTMLPrintVisitor(printWriter);
TreeTraversal treeTraversal = 
  new RecursivePreorderTreeTraversal(htmlPrintVisitor);
treeTraversal.traverse(document);
printWriter.close();

Documentation:
public class RecursivePreorderTreeTraversal
extends TreeTraversal

RecursivePreorderTreeTraversal defines a specific 
document object tree traversal algorithm for use by the
visitor design pattern. This algorithm visits the 
Parent before visiting its children. 

Documentation: 
public class HTMLPrintVisitor
extends ToXMLStringVisitor

HTMLPrintVisitor implements the Visitor interface 
in the visitor design pattern for the purpose of printing in
HTML-like format the various DOM- and XML4J-defined Nodes. 

----

Question 4.1:
15 points
What is your interpretation of the behavior of this code?
Give a brief explanation in English.
Write a DJ program that has a similar behavior.
Assume that you are given HTMLPrintVisitor.

Consider the following documentation of EndTraversalException:

public class EndTraversalException
extends TreeTraversalException

----
XML4J tree traversal exception which signals from a 
Visitor to the tree traversal algorithm that all further
traversal should be ended because the visit 
on the document object hierarchy has been successfully completed.
For example, this exception could be used by 
search Visitors that are looking for the first TXElement Node
which contains certain state data. 
----

Question 4.2:
15 points
How could EndTraversalException be added to DJ?
Give a brief discussion of the interesting issues.