  VOEvent defines the content and meaning of a standard information packet for
representing, transmitting, publishing and archiving information about a
transient celestial event, with the implication that timely follow-up is of
interest. The objective is to motivate the observation of
targets-of-opportunity, to drive robotic telescopes, to trigger archive
searches, and to alert the community. VOEvent is focused on the reporting of
photon events, but events mediated by disparate phenomena such as neutrinos,
gravitational waves, and solar or atmospheric particle bursts may also be
reported.
  Structured data is used, rather than natural language, so that automated
systems can effectively interpret VOEvent packets. Each packet may contain zero
or more of the "who, what, where, when & how" of a detected event, but in
addition, may contain a hypothesis (a "why") regarding the nature of the
underlying physical cause of the event. Citations to previous VOEvents may be
used to place each event in its correct context. Proper curation is encouraged
throughout each event's life cycle from discovery through successive
follow-ups. VOEvent packets gain persistent identifiers and are typically
stored in databases reached via registries. VOEvent packets may therefore
reference other packets in various ways. Packets are encouraged to be small and
to be processed quickly. This standard does not define a transport layer or the
design of clients, repositories, publishers or brokers; it does not cover
policy issues such as who can publish, who can build a registry of events, who
can subscribe to a particular registry, nor the intellectual property issues.
