code: public Set<String> getPropertyNames()
          {
          Set<String> propertyNames =
                  new HashSet<String>(m_attributes.size() + m_elements.size());
          for (Property property : m_attributes)
              {
              propertyNames.add(property.getLocalName());
              }
          for (Property property : m_elements)
              {
              propertyNames.add(property.getLocalName());
              }
          return propertyNames;
          }
docs: {@inheritDoc}