CSCI 5931A.1
XML Application Development
Fall 2002
Suggested Solution to Mid-Term Examination

(1) For example,

   //   Number of elements of the tree so far.
   private static int numElements = 0;
   //   Depth of the current element.  A null
   //   tree has a depth of -1.
   private static int currentDepth = -1;
   //   Sum of depth of all elements encountered so far.
   private static int totalDepth = 0;

   //   Handler methods
   public void startElement(String namespaceURI,
      String lName,
      String qName,
      Attributes attrs)
      throws SAXException
   {   currentDepth++;
      totalDepth += currentDepth;
      numElements++;
   }   //   startElement

   public void endElement(String namespaceURI,
      String lName,
      String qName)
      throws SAXException
   {   currentDepth--;
   }   //   endElement

   public void endDocument()
      throws SAXException
   {   averageDepth = (double) totalDepth / (double) numElements;
      //   does not work because of integer division:  
      //      averageDepth = totalDepth / numElements;
   }   //   endDocument

(2) (a) For example,

<xsd:simpleType name="EvenNaturalNumber">
  <xsd:restriction base="xsd:string">
    <xsd:pattern value="2|4|6|8|([1-9][0-9]*[02468])"/>
  </xsd:restriction>
</xsd:simpleType>

(b) For example:

<!ELEMENT enrollment (students, courses)>
<!ELEMENT students (student*)>
<!ELEMENT student EMPTY>
<!ATTLIST student
   id ID #REQUIRED
   lastname NMTOKEN #REQUIRED
   firstname NMTOKEN #REQUIRED>
<!ELEMENT courses (course*)>
<!ELEMENT course EMPTY>
<!ATTLIST course
   id ID #REQUIRED
   courseNumber NMTOKEN #REQUIRED
   session NMTOKEN #REQUIRED
   title NMTOKEN #REQUIRED
   students IDREFS #REQUIRED>

(c) For example:

use strict;
my $time = localtime;
print <<__END;
Content-type: text/xml

<?xml version="1.0" ?>
<servertime>
The current date &amp; time is $time
</servertime>
__END
exit 0;

(3)

(a) For example:

   private static void DeleteB (org.w3c.dom.Element element) {
      if (element == null) return;
      NodeList childNodes = element.getChildNodes();
           
//      for (int i=0; i < childNodes.getLength(); i++) {  
//      Very subtle error as there may be text nodes between elements
//      to hide the errors.
      int i=0;
      while (i <childNodes.getLength()) {
         if (childNodes.item(i).getNodeType() == Node.ELEMENT_NODE) {
            //   An element child node
            Element child = (Element) childNodes.item(i);
            if ("B".equals(child.getNodeName())) {
               element.removeChild(child);
            }
            else {
               DeleteB(child);
               i++;
            }
         }   //   if
         else
            i++;
      }   //   while
   }   //   DeleteB

(b) For example:

System.out.print(a.getFirstChild().getNodeValue());