RubyAgent

To finish the overview of the backboard operations, let’s show how to use the read operation. It only checks, if a blackboard contains a wanted tuple (in the previous posts I used the term message, but now we are more experienced :).

The following functionalities will be shown:

• Creation of an agent.
• Locating the blackboard.
• Read a message.

The agent source code is stored in the read.rb file:

require 'rinda/ring'

DRb.start_service

ts = Rinda::RingFinger.primary

result = ts.read [:message, nil], 0

puts “[0]: #{result[0]}”
puts “[1]: #{result[1]}”

See a screencast .

Firstly, start the rinda.rb code (for more details see the post about starting multi-agent system environment), then, in a separate console, start the write.rb (for more details see the post about writing a message to the blackboard) and finally, in a separate console or in the same console where you started the write.rb file, type:

ruby read.rb

The agent connects to the blackboard, reads a tuple and shows two lines:

[0]: message
[1]: Hi there!

Of course, you could repeat this step any number of times, because this operation only checks if a tuple is there.

Files to download: rinda.rb, write.rb and read.rb.

Tags: Howto, Rinda, blackboard, read

A blackboard system should support three operations: write, take, read.

• write — adds a message to the blackboard.
• take — returns a content of a message from the blackboard, but it also removes it from the blackboard. An agent, that performed the take operation, is the only one in the system, that has a content of this message.

  This operations is usually used for messages that start a task. There is no need to let other agents to start the same task.

• read — returns a content of a message from the blackboard. The message stays there, so other agents can also read a content of this message.

  This is used for messages that describe a state of the whole system — a flag. For example, a flag stop processing should be visible to all agents, so all of them will stop processing.

Tags: Introduction, blackboard, read, take, write