An extensive library of regular expression characters and operators is available for your URI filters and IP address specifications. The International Components for Unicode (ICU) open-source development project provides this library for your use. The next section provides the most frequently used expressions for this product. However, you can refer to the following Web page for a full description of the ICU regular expression library and an explanation of how to use the characters and operators for complex expressions: http://oss.software.ibm.com/icu/userguide/regexp.html