Tool interoperability using PLASTIC

SPLAT-VO can communicate with other desktop tools, for instance exchanging spectra with them, using a protocol called PLASTIC. These functions are controlled from the Interop menu in the browser window, which looks like this:

What is PLASTIC?

PLASTIC stands for the PLatform for AStronomical Tool InterConnection. It is a protocol which allows tools on the desktop to communicate with each other. Briefly, the way it works is that applications can send messages to a central hub process which will then pass them on to other applications which can respond to them in some appropriate way. The messages are things like ``load this spectrum''. Applications which currently talk PLASTIC include TOPCAT, GAIA and various tools from the AstroGrid project.

You can find more information about how it works, what applications are compatible, and how it can be useful at the PLASTIC web site.

How do I use PLASTIC with SPLAT-VO?

In order for PLASTIC communications to work, a PLASTIC hub must be running on your machine. It is generally best to start this outside of SPLAT-VO. The recommended way to do this is currently to run the AstroGrid Workbench, which can be started using Java WebStart by following links on the AstroGrid web site. It is possible however to start the hub using either the Start internal PLASTIC hub or Start external PLASTIC hub menu items. The internal one will terminate when you exit SPLAT-VO, but the external one will continue running until it is explicitly stopped. For convenience these two options are also available from the command-line as the --hub and --exthub switches.

If the hub is running when SPLAT-VO starts up, SPLAT-VO will connect to it (``register'') automatically. If you start the hub while SPLAT-VO is already running, you can connect to it by selecting the Register with PLASTIC option from the Interop menu, or wait for a while and the presence of the hub will be automatically detected. When registered, SPLAT-VO will listen out for messages from other applications and act on them. You will also be able to send messages to other applications. If you want to stop SPLAT-VO responding to any such messages, you can select Unregister with PLASTIC from the same menu.

The Show Registered Applications menu item will display a little window that gives the names of applications currently registered. This will show you which other tools are in a position to send messages to or receive them from SPLAT-VO.

What PLASTIC facilities does SPLAT-VO support?

Currently, SPLAT-VO's PLASTIC interaction is confined to receiving spectra from, and sending spectra to, other applications.

Normally, if another PLASTIC application sends spectral data to SPLAT-VO, it will respond by attempting to add it to the global list just as if you had loaded it in the usual way. This is usually what you want to happen, but two checkbox items are provided on the Interop menu which allow you to turn this behaviour off: Accept spectra and Accept 1d FITS. If you uncheck these, then incoming requests to load spectral data or 1-dimensional FITS files respectively will be ignored.

You can also perform the opposite trick, take a spectrum which is displayed in SPLAT-VO and send it to one or all of the other tools currently registered with PLASTIC. To do this select one of the Broadcast spectrum or Send spectrum to ... items. The Broadcast action sends the data to all listening tools. The Send action sends only to a single selected tool; you choose it from the submenu to the right. Only tools which (claim they) know what to do with spectral data will be listed; if none of the currently-registered tools is prepared to accept data in that format, the Send options will be unavailable.