Notice the difference between a _notice and a _status (or several other method families):

A _notice is always an unsolicited event happening, like somebody logging in or changing her presence data.

A _notice is never issued as a reply to anything and a _notice always implies that something has changed.

It is therefore the second most important family after _message and the quintessential element making PSYC a push technology.

Still, _notice should not carry critical information as it may be delivered by UDP and not arrive safely under extreme circumstances.

See also specific notification methods.