A term from AlistairCockburn's ''AgileSoftwareDevelopment'':

	 :	"An information radiator displays information in a place where passersby can see it. With information radiators, the passersby don't need to ask questions; the information simply hits them as they pass.

	 :	"Two characteristics are key to a good information radiator. The first is that the information changes over time. This makes it worth a person's while to look at the display... The other characteristic is that it takes very little energy to view the display."

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Whiteboard in the hall is good, scrolling LED display is not.

''"Radiator" implies an active component to this; what is being radiated here? It seems to me to be a completely passive information source. This is not like a server that broadcasts its availability or the fact that it has new services available. This is more like a community bulletin board that simply has junk tacked up all over the place in public view. Is there a pattern for this? It certainly isn't Publisher/Subscriber or Observer.''

''"Radiator" does not imply an active component to me. In my house I have radiators. Their job is to sit there and be warm, so that anyone who stands next to them gets warm. As a by-product the room gets warm.''

"Radiator" does imply an active component to me. The radiators in your house are actively radiating heat. You can't ''see'' heat, but that doesn't mean the radiator is just sitting there passively. You might as well say that the Sun is passive. Similarly, an information radiator's job is to radiate information, so that anyone who looks at it gets informed. Conversely, I think an information source that requires you to take action to extract information from it is "passive."

[If I remember correctly, when it comes to heating/cooling systems "active" basically means that it uses a fan/pump, and "passive" means it doesn't.  Most radiators that I'm familiar with don't have fans/pumps (they rely on the heat source to provide it), and would therefore be considered passive.]

*Passive = Heat rises, and cold falls, naturally: thus is the engine that provides the circulation.
*Active = Heat and cold can't naturally flow, because of design limitations, thus a pump/fan/etc. must be used as the engine that provides the circulation.

The only comparison that I see here, is that like the way a heat radiator radiates heat to anyone near, the Information Radiator radiates information to anyone near.  Simple.  I like it.  No mater whether the engine that runs it is passive or active, the result is the same.
  
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One obvious extension of this idea would be to set up a small PC linked to a projector which does nothing but display the current status of the build, UnitTest coverage, and various metrics about your code base. If you only display a high-level view of essential data then everyone who walks by can see the state of play. I've seen this used for monitoring the status of a large number of servers, and it works well. 

If we could boil down the current status of a project to a page of information (preferably in some visual format) with perhaps another screen displaying historical data, there would be clear benefits for project tracking. I remember discussing this with SteveFreeman once at the ExtremeTuesdayClub as a way of using a visualization tool like Pasta (Compuware's Package Structure Analysis Tool at http://javacentral.compuware.com/pasta/) to identify bad check-ins. By colour-coding the metrics and hooking a visualization tool to CVS or CruiseControl we end up with a system where, if someone checks in 'bad code', (according to your metrics) everybody notices in a non-intrusive way. I rather like the idea of a bad check-in immediately leading to a red wall. -- AdewaleOshineye

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Compare: InformationRefrigerator and BigVisibleChart