IETF RFC 4661 PDF

The SIP event notification framework describes the usage of the Session Initiation Protocol (SIP) for subscriptions and notifications of changes to a state of a resource. The document does not describe a mechanism whereby filtering of event notification information can be achieved. Filtering is a mechanism for defining the preferred notification information to be delivered and for specifying triggers that cause that information to be delivered. In order to enable this, a format is needed to enable the subscriber to describe the state changes of a resource that cause notifications to be sent to it and what those notifications are to contain. This document presents a format in the form of an XML document.