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 table" or "point at this position on the sky". Applications which currently talk PLASTIC include TOPCAT, Aladin 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.
In order for PLASTIC communications to work, a PLASTIC hub must be running on your machine. This is not part of GAIA and you will have to start it up separately. 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 website.
If the hub is running when GAIA starts up, GAIA will connect to it ("register") automatically. If you start the hub while GAIA is already running, you can connect to it by selecting the "Register" option from GAIA's "Interop" menu. When registered, GAIA 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 GAIA responding to any such messages, you can select "Unregister" from the same menu.
In most cases, sending a PLASTIC message from GAIA is controlled using one of its "Interop" menus. For a given action these often have two ways to transmit a given message: "Broadcast ..." and "Send to ...". For "Broadcast", all registered applications which understand it are invited to do something with the message. For "Send to" there is a submenu which allows you to choose which single application to direct the message to. Only applications which claim to understand the particular message will appear on such submenus (which means that this submenu may be empty, depending on what other PLASTIC-aware tools you've got running).
GAIA can both send and respond to messages in two general
application areas: image-related and catalogue-related
(a third category of housekeeping messages is not discussed here).
The messages and how to use them are listed below; the
message ids (strings starting "
the formal identifiers for these messages - if you are not an applications
programmer you can ignore these.