In order to discover whether another entity supports this protocol, an entity MUST use &xep0030;.

It can be desirable (and, in some contexts, necessary) to determine if the intended recipient of an XML stanza supports a specific header (e.g., the "Classification" header) before sending information that may depend on that header. Therefore, implementations of this protocol MUST advertise which particular SHIM headers they support when queried via disco#info at the well-known service discovery node 'http://jabber.org/protocol/shim'.

The values of the 'var' attribute MUST be of the form "http://jabber.org/protocol/shim#header", where "header" is to be replaced with the name of the header as registered with the ®ISTRAR; (see below).

The Classification header enables a sender or other entity to classify a stanza according to some classification scheme. The values of the XML character data contained within this header are out of scope for this document, since they are determined by the using application. Note: This header may be security-sensitive (see the Security Considerations for details).

The Date header is defined by RFC 2822 and therefore follows the date and time format defined by RFC 2822; while this header is thus useful for translating email messages into XMPP stanzas, it is not consistent with &xep0082;. Therefore we define the "Created" header, which specifies the date and time when a stanza was created by the originating entity, where the value conforms to the DateTime profile specified in XEP-0082.

The Distribute header enables a sender to specify whether the stanza may be further distributed by the recipient to other entities on the network. The allowable values for this header are "true" and "false". If the sender specifies a value of "false", the recipient MUST NOT further distribute the stanza or any information contained therein; if the sender specifies a value of "true", the recipient MAY further distribute the stanza or any information contained therein; if the value is anything other than "true" or "false" and the recipient does not understand the value, the recipient MUST assume the default value of "false". This header is semantically equivalent to the "Distribute" flag defined in &geoprivpol;. (The HTTP "Max-Forwards" header is not appropriate for this usage, since it defines proxy and gateway behavior rather than recipient behavior.) Note: This header may be security-sensitive (see the Security Considerations for details).

The Store header enables a sender to specify whether the stanza may be stored or archived by the recipient. The allowable values for this header are "true" and "false". If the sender specifies a value of "false", the recipient MUST NOT store the stanza or any information contained therein; if the sender specifies a value of "true", the recipient MAY store the stanza or any information contained therein; if the value is anything other than "true" or "false" and the recipient does not understand the value, the recipient MUST assume the default value of "false". Note: This header may be security-sensitive (see the Security Considerations for details).

It may be useful to specify that the information contained in a stanza is valid only for a limited period of time. Such is the function of the "TTL" header, the value of which is some number of seconds since the creation of the stanza. Note well that this header is purely informational and MUST NOT be used for routing or delivery of XML stanzas, since that function is already served by &xep0079;. A stanza that includes the "TTL" header SHOULD also include a "Created" header so that the recipient can properly process the stanza.

One situation in which both the "Created" and "TTL" headers might prove valuable is the broadcasting of structured presence information, such as a calendar-generated notification that a user will be in a meeting for the next hour:

Another potential application is specifying a time to live for Service Discovery results, which helps other entities know how long to cache such information:

It can be useful to specify that the information contained in a stanza is more or less time-sensitive (e.g., in order to help the recipient determine whether to attend to the information immediately or to delay attending to the information). Such is the function of the "Urgency" header, the value of which is "high", "medium", or "low". One use of the header is Sieve notifications (see &sievenotify;) sent via XMPP, as specified in &sievenotifyxmpp;.

The XMPP Registrar includes 'http://jabber.org/protocol/shim' in its registry of protocol namespaces (see &SHIMHEADERS;).

The XMPP Registrar includes 'http://jabber.org/protocol/shim' in its registry of well-known Service Discovery nodes.

The XMPP Registrar maintains a registry of SHIM headers.