VOEventNet Overview & Status

Transcript

1. John Swinbank, swinbank@transientskp.org Vice Chair, IVOA Time Domain Interest Group

   LOFAR TKP Project Meeting 3 December 2012, Amsterdam VOEventNet Overview & Status

2. Transient Notifications

3. Transient deluge • LSST promises us 2×106 transients/night (Two! Million!)

   • How will you decide what’s interesting for your science case? That’s a lot of ATels to read... • The faster your follow-up, the (potentially) better your science

4. Standard tools • A solved problem (sorta) • XML •

   eXtensible Markup Language • “defines a set of rules for encoding documents in a format that is both human-readable and machine-readable” • Widespread acceptance means many off-the- shelf tools, libraries and procedures.

5. VOEvent Who? What? When? How? So what?

6. Transport • VOEvent is transport agnostic • Write it down,

   send an e-mail, engrave on stone tablets, ... • VOEvent Transport Protocol Alasdair Allan, Robert B. Denny, John Swinbank IVOA Note, Version 1.2 coming soon Draft version on request

7. VTP Overview Broker Author Subscriber VOEvent Acknowledge Subscriber Subscriber Keep

   A live Keep A live VO Event VO Event Keep A live Keep A live

8. VOEvent Backbone Broker Broker Broker Broker Watch out for loops!

9. Comet http://comet.transientskp.org/

10. Value Added Services • A broker may provide additional services

    to its subscribers • Filter event streams • Any node may provide additional services based on events received • Store in a database • Display on a web page • Perform a follow-up observation(!) http://www.skyalert.org/

11. Stream Filtering by Comet • “XPath, the XML Path Language,

    is a query language for selecting nodes from an XML document. In addition, XPath may be used to compute values (e.g., strings, numbers, or Boolean values) from the content of an XML document” (Wikipedia) • Comet lets subscribers specify an XPath expression and only forward events for which it evaluates to true (or non-zero) • /*[local-name()="VOEvent" and @role!="test"] • //Who[AuthorIVORN="ivo://lofar.transients/"] • This is a Comet “special”, not an IVOA standard.

12. Breaking news! FAKE

13. A Short PGP Primer Alice Bob Alice wants to communicate

    securely with Bob ? And sends half to Bob Alice can sign with her key. Bob can verify the signature. A signature guarantees the sender of the message had possession of Alice’s key. She generates a PGP “key” PGP is an internet standard (RFC 4880) with various free & commercial implementations.

14. Bits, bytes & infosets • A PGP signature guarantees the

    bits which make up the message are unchanged <element>value</element><element2>value2</element2> <element>value</element> <element2>value2</element2> • What is the legitimate role of a broker or repository?

15. Standards & Support • Digital Signatures in VOEvent Messages, Robert

    B. Denny & John Swinbank, IVOA Note, Version 2.0 coming soon (draft version by request). • Supported by the development version of Comet. • ...will this address all your use cases?

16. Also on the horizon... • VOEventRegExt • How do you

    find a VOEvent broker? • How do you get hold of an event given an IVORN? • Time series data model • ... others • Please get involved! http://www.voevent.org/