docs: public String toXML()
      {
          String eol = System.getProperty("line.separator");
          RepositoryTags tags = RepositoryTags.getInstance();
  
          // The result
          String result = "     ";
  
          switch (this.fieldSource)
          {
              case SOURCE_FIELD :
                  result += " " + tags.getOpeningTagNonClosingById(RUNTIME_ARGUMENT);
                  result += " " + tags.getAttribute(FIELD_REF, this.fieldRefName);
                  result += " " + tags.getAttribute(RETURN, String.valueOf(this.returnedByProcedure));
                  result += "/>";
                  break;
              case SOURCE_VALUE :
                  result += " " + tags.getOpeningTagNonClosingById(CONSTANT_ARGUMENT);
                  result += " " + tags.getAttribute(VALUE, this.constantValue);
                  result += "/>";
                  break;
              case SOURCE_NULL :
                  result += " " + tags.getOpeningTagNonClosingById(RUNTIME_ARGUMENT);
                  result += "/>";
                  break;
              default :
                  break;
          }
  
          // Return the result.
          return (result + eol);
      }