3.1.4 Message Processing Events and Sequencing Rules
The following high-level sequence diagram illustrates the operation of the protocol.

Figure 5: Protocol operation
The state data acquired from server bootstrapping previously described in section 3.1.3 MUST be retained on the server. Beyond this, no other state data is required on the server. The server MAY retain additional state data as an optimization, but it is not required. These operations are discussed in more detail in the following sections.
Note The following defined methods MUST contain a VersionData element in the SOAP header (as specified in [SOAP1.1]). For information on the VersionData element, see section 2.2.3.3.