A channel type for representing a list of people on the server which is not used for communication. This is intended for use with the interface Channel.Interface.Group for managing buddy lists and privacy lists on the server. This channel type has no methods because all of the functionality it represents is available via the group interface.

There are currently two types of contact list: HANDLE_TYPE_LIST is a "magic" server-defined list, and HANDLE_TYPE_GROUP is a user-defined contact group.

For server-defined lists like the subscribe list, singleton instances of this channel type should be created by the connection manager at connection time if the list exists on the server, or may be requested by using the appropriate handle. These handles can be obtained using RequestHandles with a Handle_Type of HANDLE_TYPE_LIST and one of the following identifiers:

• subscribe - the group of contacts for whom you receive presence
• publish - the group of contacts who may receive your presence
• hide - a group of contacts who are on the publish list but are temporarily disallowed from receiving your presence
• allow - a group of contacts who may send you messages
• deny - a group of contacts who may not send you messages
• stored - on protocols where the user's contacts are stored, this contact list contains all stored contacts regardless of subscription status.

A contact can be in several server-defined lists. All lists are optional to implement. If RequestHandles or RequestChannel for a particular contact list raises an error, this indicates that the connection manager makes no particular statement about the list's contents; clients MUST NOT consider this to be fatal.

If a client wants to list all of a user's contacts, it is appropriate to use the union of the subscribe, publish and stored lists, including the local and remote pending members.

For example in XMPP, contacts who have the subscription type "none", "from", "to" and "both" can be respectively in the lists:

• "none": stored
• "from": stored and publish
• "to": stored and subscribe
• "both": stored, publish and subscribe

These contact list channels may not be closed.

For user-defined contact groups, instances of this channel type should be created by the connection manager at connection time for each group that exists on the server. New, empty groups can be created by calling RequestHandles with a Handle_Type of HANDLE_TYPE_GROUP and with the name set to the human-readable UTF-8 name of the group.

User-defined groups may be deleted by calling Close on the channel, but only if the group is already empty. Closing a channel to a non-empty group is not allowed; its members must be set to the empty set first.

On some protocols (e.g. XMPP) empty groups are not represented on the server, so disconnecting from the server and reconnecting might cause empty groups to vanish.