code: function(wildCard, singleChar, escapeChar) {
          if (wildCard == ".") {
              throw new Error("'.' is an unsupported wildCard character for " +
                              "OpenLayers.Filter.Comparison");
          }
          
  
          // set UMN MapServer defaults for unspecified parameters
          wildCard = wildCard ? wildCard : "*";
          singleChar = singleChar ? singleChar : ".";
          escapeChar = escapeChar ? escapeChar : "!";
          
          this.value = this.value.replace(
                  new RegExp("\\"+escapeChar+"(.|$)", "g"), "\\$1");
          this.value = this.value.replace(
                  new RegExp("\\"+singleChar, "g"), ".");
          this.value = this.value.replace(
                  new RegExp("\\"+wildCard, "g"), ".*");
          this.value = this.value.replace(
                  new RegExp("\\\\.\\*", "g"), "\\"+wildCard);
          this.value = this.value.replace(
                  new RegExp("\\\\\\.", "g"), "\\"+singleChar);
          
          return this.value;
      }
docs: APIMethod: value2regex
  Converts the value of this rule into a regular expression string,
  according to the wildcard characters specified. This method has to
  be called after instantiation of this class, if the value is not a
  regular expression already.
  
  Parameters:
  wildCard   - {Char} wildcard character in the above value, default
  is "*"
  singleChar - {Char} single-character wildcard in the above value
  default is "."
  escapeChar - {Char} escape character in the above value, default is
  "!"
  
  Returns:
  {String} regular expression string