What is PGM? What is OpenPGM?

Well lets start by saying PGM is the name of a internet, lower-case "i", communications protocol, and OpenPGM is an implementation of that protocol.  A communications protocol being the definition of how two or more computers or electronic devices communicate with each other.  For example you just enjoyed a good slice of cherry pie and damn fine cup of coffee and you wanted to tweet it to your friends, you tap the message into your phone and hit a button, then by magic the message appears on your microblog.  Between your phone's Twitter app' and the Twitter website your tweet message has been sent following a predefined communications protocol.

There is a subtle difference between the Internet, upper-case "I", and an internet, lower-case "i", the former is the name for the public network where we can access Facebook and Twitter, the latter is the generic term for a group of interconnected networks.  This means we could find PGM on the Internet or we could find it on other non-public networks such as within a stock exchange's trading system or communicating physics of the Higgs Boson at the Large Hadron Collider.

So what is special about PGM?

The erhu is a Chinese two-stringed bowed musical instrument and not commonly found in Western music.  If you wanted to listen to a recital of Sanmen Capriccio a convenient choice might be to watch a performance by Yang Ying on YouTube.  For a live performance you might tune in the radio and listen alongside other fans of huqin.  On the Internet you may find an Internet radio station to listen on but there is fundamental limitation on how many fans can be plugging in.  Say Girls Generation announced a online concert tonight the stampede from eager fans may overload the site and crash the network as the concert site has to stream a duplicate copy of the event to each and every listener.  The PGM protocol allows one sent stream of data to be received by multiple recipients, the fan-out of the stream to each recipient being managed by the network instead of say the host concert site.

Why should I choose OpenPGM?

So PGM is the protocol on paper, digitally at least, you need an actual implementation for something to start looking like it will work.  There are a selection of vendors providing commercial solutions, including Microsoft, IBM, and TIBCO,  and a variety of open source projects as long as your preferred platform is FreeBSD.  So an open source implementation that works on multiple platforms, is compatible with existing vendor solutions, and is even faster and more flexible sounds like a good choice, then have a look at OpenPGM.