John Swinbank, [email protected]
Vice Chair, IVOA Time Domain Interest Group
LOFAR TKP Project Meeting
3 December 2012, Amsterdam
Overview & Status
• LSST promises us 2×106 transients/night
• 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
• A solved problem (sorta)
• 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.
• 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
Value Added Services
• A broker may provide
additional services to its
• 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
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
• 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"]
• This is a Comet “special”, not an IVOA standard.
A Short PGP Primer
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.
Bits, bytes & infosets
• A PGP signature guarantees the bits
which make up the message are
• What is the legitimate role of a broker
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
• ...will this address all your use cases?
Also on the horizon...
• 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!