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### 9.3 Messages Transmitted

This section describes the messages which TOPCAT can transmit to other tools which understand the SAMP or PLASTIC protocol, and how to cause them to be sent. Approximately the same behaviour results for either SAMP or PLASTIC, except as noted.

In most cases you can choose two ways to transmit a message from TOPCAT:

Broadcast
  Broadcasts the message to all other applications currently registered with the hub which understand that message.
Send
  Sends the message to a single application which you select. The suitable applications (ones which are registered with the hub and claim to understand that message) are listed and you can choose one.

Examining the list of applications in the Send menu gives you an indication of which ones a Broadcast would broadcast to. Note however that just because an application appears in this list doesn't necessarily mean it will do something substantial with the message, for instance some applications register with the hub just to monitor traffic. In general the Broadcast and Send actions will be disabled (greyed-out) if TOPCAT is not registered with a hub, or if there are no applications listening which claim to support the relevant message.

Below is a list of places you can cause TOPCAT to transmit messages. The SAMP MTypes and PLASTIC message IDs are listed along with the descriptions; unless you are a tool developer you can probably ignore these.

Transmit Table
  The Control Window's Interop menu provides Broadcast Table and Send Table options which cause the currently selected table to be transmitted to other listening applications. They are invited to load the table in its current ("apparent") form. The Broadcast action is also available in the toolbar.

  SAMP MTypes: `table.load.votable` or `table.load.fits`; PLASTIC Message IDs: `ivo://votech.org/votable/load` or `ivo://votech.org/votable/loadFromURL`

Transmit Subset
  The Subset Window's Interop menu contains Broadcast Subset and Send Subset options. These cause the selected subset to be sent to other listening applications (these actions are only available when one of the subsets is currently selected). Applications are invited to highlight the rows corresponding to that subset. Note this will only have an effect if the other application(s) are displaying the table that this subset relates to. This will be the case in one of two situations: (1) the table has been loaded from the same URL/filename by the other tool(s) or (2) the other tool(s) have acquired the table because it has already been broadcast using SAMP/PLASTIC.

  Also, whenever a new subset is created, for instance by entering an algebraic expression or tracing out a region on a plot (see Section 3.1.1), you have the option of transmitting the subset directly to one or all listening applications as an alternative to adding the new subset to the table's subset list.

  SAMP MType: `table.select.rowList`; PLASTIC Message ID: `ivo://votech.org/votable/showObjects`

Transmit Row
  The ControlWindow has a Broadcast Row checkbox by the Activation Action selector. If this is selected, then any time you activate a row (e.g. by clicking on the corresponding point in a plot) other applications who are looking at the same table are invited to highlight that row in their copy of the table. As for Transmit Subset above, this will only have an effect if the other application(s) are displaying the same table.

  A similar facility is available as the Transmit Row option in the Activation Actions window itself - the checkbox is just a convenience for a commonly-used option.

  SAMP MType: `table.highlight.row`; PLASTIC Message ID: `ivo://votech.org/votable/highlightObject`

Transmit Coordinates
  Another Activation Action is Transmit Coordinates. In this case when you activate a row (e.g. by clicking on the corresponding point in a plot) other applications are invited to point out the sky position corresponding to the row which is activated, for instance by placing a cursor over it. The table columns which correspond to Right Ascension and Declination must be selected for this to work.

  SAMP MType: `coord.pointAt.sky`; PLASTIC Message ID: `ivo://votech.org/sky/pointAtCoords`

Transmit Image
  The Density Plot produces a 2-d histogram which is actually an image. Its Interop menu provides Broadcast Image and Send Image options which will send this (as a FITS image) to other applications which can display it in some way. This is a useful supplement to the facilities of the Density Plot window, since it doesn't have very sophisticated image display features (variable colour maps, contour plots etc).

  Also, the View URL as Image Activation Action option allows you to identify a column which contains an image URL and to send it to a suitable image viewer or viewers.

  SAMP MType: `image.load.fits`; PLASTIC Message ID: `ivo://votech.org/fits/image/loadFromURL`

Transmit Spectrum
  The View URL as Spectrum Activation Action option allows you to identify a column which contains a spectrum URL and to send it to a suitable spectrum viewer or viewers.

  SAMP MType: `spectrum.load.ssa-generic`; PLASTIC Message ID: `ivo://votech.org/spectrum/loadFromURL`

Transmit Resource List
  The Registry Query Panel present in most of the Virtual Observatory windows allows you to send lists of VO registry resource identifiers to other applications which can make use of them. Note this only works in SAMP mode, not for PLASTIC.

  SAMP MTypes: `voresource.loadlist.cone`, `voresource.loadlist.siap`, `voresource.loadlist.ssap`

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk