1. VOEvent and the Registry Introducing VOEventStream and VOEventService Roy Williams Caltech

2. VOEvent Roles * An Author is anyone (or any organization) creating scientific content suitable for representation as a sky transient alert. An author will typically register with the IVOA registry, so that the element of VOEvent packets can be small and reusable, expressing only the IVOA identifier needed to retrieve the contact information for the author. * A Publisher receives alerts from one-or-more authors, and assigns a unique identifier to each resulting packet. Either the author or the publisher generates the actual XML syntax of the event, but the publisher is responsible for the validity of the packet relative to the VOEvent schema. Publishers will register with the IVOA registry as described below. * A Repository subscribes to one or more VOEvent streams, persists packets either permanently or temporarily, and runs a service that allows clients to resolve identifiers and apply complex queries to its holdings. A given packet had one Publisher but may be held in more than one Repository. Public repositories will register with the IVOA registry. * A Subscriber is any entity that receives VOEvent packets for whatever purpose. Subscribers can find out how to get certain types of events by consulting the lists of publishers and repositories in the IVOA registry. A subscription is a filter on the stream of events from a publisher: the subscriber is notified whenever certain criteria are met. For example, the filter may involve the curation part of the event (e.g., "all events published by the Swift spacecraft"), its location ("anything in M31"), or it may reference the detailed metadata of the event itself ("whenever the cosmic ray energy is greater than 3 TeV"). * A Broker or Relay, also sometimes known as a Filter, is any combination of the atomic roles of Publisher, Repository, or Subscriber that also offers arbitrary application-level functionality. See the IVOA VOEvent Transport Note [21] for further discussion.

3. VOEvent queries “Select MOA events where Base_magnitude < 20” Must know Param dictionary to form query Associate Param dictionary with event stream Example MOA microlensing event ivo://nvo.caltech/voeventnet/moa#MOA-2001-BLG-10

4. What is a VOEventStream? An Event Stream is a set of events, some past, some future, which: Are homogeneous Have unified scientific purpose, meaning, & leadership Use the same vocabulary

5. What is a VOEventService? An Event Service handles events from a single Event Stream May be many Services for each Stream Service may offer query capability Service may offer subscription capability

6. VOEventStream has science author and meaning and parameter set used VOEventServer serves a specific VOEventStream may have query capability may have subscription capability

7. VOEventStream Param mag Param color VOEventServer Queries on repository VOEventServer Accepts subscription requests VOEventServer Queries on repository VOEventServer Accepts subscription requests

8. Resolving an event identifier ivo://blah#345 IVORN for VOEventStream is ivo://blah Query registry: –Which VOEventServices serve ivo://blah and have query capability? Choose one Send query to that one: –Please resolve ivo://blah#345

9. VOEventStream resource record 1 Title –Short Name –Subject –Description –ADS bibcode –Reference URL Creator Name & Date –Contributor, Version Observation Facility and Instrument Coverage –Spatial coverage (allsky, circle, box) –Waveband –Temporal start/end

10. VOEventStream resource record 2 List of Group –Containing Param Name, UCD, unit, datatype, Description Example: Johnson R photometric measurement :-)

11. VOEventServer resource record 1 Serves a VOEventStream –Where to query the catalog of past events –How to subscribe to future events title/curation/content as usual with any VOResource AND Which VOEventStream are we serving ivo://nvo.caltech/VOEventNet/Essence AND http://nvo.caltech.edu:8080/voeventnet/seap?stream=catalina& GET application/xml Capability for SEAP = query past events

12. VOEventServer resource record 2 roy@caltech.edu events from OGLE which are really bright just the finding chart Subscription capability –Interfaces offered: Email, Jabber, TCPvanilla, text message, web browser Endpoint for each Subscription request for future events

13. Broker Collects “best” events from many subscriptions Emits new VOEventStream Gives new IVORN to those events –Citation to original event ivo://uraniborg.hven#572-11-11/0001

14. A Broker Collects interesting events from others ivo://streamX#123 ivo://streamY#666 Builds a new stream ivo://myStream Gives each event a new ID ivo://myStream#678 Cites the original cite=“copy” New ID Cite Original ID