VOEvent
From EStar
About
The eSTAR project is an active collaborator in the IVOA's efforts to standardise event notification in the era of the Virtual Observatory (VO), and Alasdair Allan represents the project on the IVOA's VOEvent working group.
The objective of the VOEvent effort is to define the content and meaning of a standard information packet for representing, transmitting, archiving, and publishing a discovery of an immediate event in the sky. We will call this packet VOEvent. The objective is to drive robotic telescopes, to drive archive searches, to alert the community, and to build interoperable archives. Structured data is the target here, rather than natural language, so that automated systems can be most effective in interpreting VOEvent packets.
Event Feeds
In addition to running an event broker and repository, the eSTAR project also makes event notices availabe in (near) real time via RSS 2.0 feeds. You can subscribe to these as normal using a news aggregator. However if you do not already use a news aggregator, there are many freely available clients that you can use to read the RSS feeds.
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eSTAR native (including OGLE messages)
- RAPTOR/TALONS (including GCN translation)
- Caltech (including GCN translation and SDSS messages)
- NOAO (including ESSENCE messages)
- Robonet-1.0 native
Event messages are also broadcast as tweets over twitter.
Google Sky (Beta)
We're currently experimenting with Google Sky and are feeding a live network link with all the event notices going across the backbone. This should be viewed as experimental and still in development and may temporarily disappear or break with little or no notice.
Time line Interfaces (Beta)
As part of the project's work on event visualisation, have have now rolled out an open beta-releases of the OGLE Event Timeline and SDSS Event Timeline pages. At the top of each page is an event timeline, with two independently scrollable bars (the upper in days, the lower in months), which you can click and then drag to show previous events. The OGLE or SDSS event data is also displayed normally in table form below the timeline interface.
Manual Submission (Beta)
In collaboration with Thinking Telescope Project (RAPTOR) at LANL, the eSTAR project has rolled out a closed beta-release of a manual injection system 
for VOEvent messages. This allows you to easily build fairly complicated event messages which will be distributed onto the event network backbone in real time by the eSTAR event broker, as well as being made available via RSS feed
The service is currently restricted to registered users only, however if you want to request an username and password for the service please email Alasdair Allan with your full name, preferred contact email and phone number and your institutional/project affiliation.
VOEvent Documentation & Software
The latest draft of the VOEvent standard is available from the IVOA website, while a reference Perl implementation of a VOEvent parser is available from the VOEvent Sourceforge Project.
While pre-bunded tarballs are available, since the software is under active development it is recommended that you should download the parser Perl module directly from the project's CVS server.
The VOEvent software can be checked out from the Sourceforge CVS repository through anonymous (pserver) access with the following instruction set. When prompted for a password for anonymous, simply press the Enter key.
cvs -d:pserver:anonymous@voevent.cvs.sourceforge.net:/cvsroot/voevent login
cvs -d:pserver:anonymous@voevent.cvs.sourceforge.net:/cvsroot/voevent co -P perl_modules
A sample client for connection to a mini-interop compliant event publisher (or broker) is also available.
Protocols
The current protocol for the exchange of VOEvent documents was agreed under a handshake agreement during the mini-interop meeting following the 2nd VOEvent Workshop in Tucson, AZ, in December 2005.
Transport
These are obviously going to be divided into two classes, push and pull transport standards. A minimum implementation for a VOEvent Publisher role, agreed at the mini-interop meeting in December 2005, is to provide push subscription via vanilla TCP and pull subscription via RSS2.0. There was also an agreement to experiment with other protocols, and eSTAR is currently prototyping with both PLASTIC and SOAP protocols to allow event injection and delivery.
Both the Protocol and Transport standards agreed at the mini-interop, and prototyped by the working group are currently being codified into an IVOA Note.
Architecture
Although the precise architecture of the emerging event network is currently under debate. There are currently 5 proposed "atomic" roles involved in transporting VOEvent messages across the VO. These are:
- Author
- Publisher
- Subscriber
- Relay
- Repository
and then we have Brokers which combine 2 or more of the above roles.