This read-write CvUriClassPattern object holds a regular expression used to match the phone-context attribute in a sip: URI, unused if left as a zero-length string, and mutually exclusive with cvCommonUriClassCfgURIPattern being set. Administrators use it to classify SIP calls based on the phone-context parameter, which disambiguates locally significant phone numbers by indicating their numbering context. For example, an admin supporting multiple regional numbering plans could use this pattern to classify calls by which regional phone-context they're tagged with.