Conference Event Package Data Format Extension for Centralized

Members of the IETF Centralized Conferencing (XCON) Working Group have
published an initial Internet Draft for "Conference Event Package Data
Format Extension for Centralized Conferencing (XCON)." The XCON
framework defines a notification service that provides updates about
a conference instance's state to authorized parties using a notification
protocol. The "Data Format Extension" memo specifies a notification
mechanism for centralized conferencing which reuses the SIP (Session
Initiation Protocol) event package for conference state. Additionally,
the notification protocol specified in this document supports all the
data defined in the XCON data model (i.e., data model as originally
defined in RFC 4575) plus all the extensions, plus a partial notification
mechanism based on XML patch operations. Section 5.4 provides an XML
Schema for Partial Notifications. Generating large notifications to
report small changes does not meet the efficiency requirements of some
bandwidth-constrained environments. The partial notifications mechanism
specified in this section is a more efficient way to report changes in
the conference state. In order to obtain notifications from a conference
server's notification service, a client subscribes to the 'conference'
event package at the server as specified in RFC 4575. The NOTIFY
requests within this event package can carry an XML document in the
"application/conference-info+xml" format. Additionally, per this
specification, NOTIFY requests can also carry XML documents in the
"application/xcon-conference-info+xml" and the
"application/xcon-conference-info-diff" formats. A document in the
"application/xcon-conference-info+xml" format provides the user agent
with the whole state of a conference instance. A document in the
"application/ xcon-conference-info-diff+xml" format provides the user
agent with the changes the state of the conference instance has
experimented since the last notification sent to the user agent.