Here is an example of a domain specific library/language I have created
to start and manage a distributed (Java-based) agent society for a DARPA
program I work on. The whole point is to load a configuration of an
Agent society from a database (in this case in MySQL). It then builds a
“society” composed of Hosts, Nodes and Software Agents that run across
JVMs in a (40 machine) network.
I will (through comments) walk through this code.
···
require ‘cougaar/controller’
Cougaar is the agent technology (www.cougaar.org)
This loads all the domain specific classes/modules
include Cougaar
Pick a (predefined) experiment and get the Society definitions
csmart = CSmartDatabase.connect(“u101”, “db”)
society = csmart.build_society(“Experiment 1”)
csmart.close
we now have a “Society” composed of Hosts, Nodes and Agents
where Hosts=computers
Nodes=JVM process
Agents=software agent
Get the controller and run the Society
controller = society.controller
This controller has lots of domain specific event management
methods.
controller.connect_to_jabber(“acme”, “alpha”)
We use Jabber to control all the distributed ruby servers that
are used to start/event/control/stop the (java-based) society.
controller.enable_cougaar_events
CougaarEvents are feedback (XML) events from the Agents sent
back to us via Jabber.
controller.on_oplan_ready do |controller|
puts “Sending OPlan”
controller.publish_oplan
end
controller.on_gls_ready do |controller|
puts “Sending GLS Root”
controller.send_gls_root
end
These events (oplan and gls) are domain specific. The
solution is a distributed logistics application where
oplan is Operations Plan and gls is the Logistical
root task. Notice the use of Ruby blocks to act as
“listeners”
trap(“INT”) { controller.stop_society }
Trap ^C to send an instant message to stop society and
clean up all the java processes.
controller.start_society
That’s it. It has lots of additional domain capabilities like stressing
the CPUs that these agents run on, performing actions at timed
intervals, etc. Ruby controls the whole shooting match via Jabber.
What this provided to the DARPA program we are using this on is the
ability to have folks that understand this domain to write scripts (once
they are trained on the dialect). As they get more comfortable, they
learn more Ruby code to enable looping experiments, capturing data, etc.
Regards,
Rich
-----Original Message-----
From: dave@thomases.com [mailto:dave@thomases.com] On Behalf Of Dave
Thomas
Sent: Thursday, August 22, 2002 2:07 PM
To: ruby-talk ML
Subject: Re: SV: A Repeat: New Language After Ruby?Thomas Søndergaard tsondergaard@speakanet.com writes:
As I do so often, I now feel tempted to quote the pragmatic
programmers. From the paper “Never Build an Application”
(http://www.pragmaticprogrammer.com/ppllc/papers/1998_03.html) I’ve
selected two interesting quotes:
“Library design is language design”
“Design a domain specific ‘language’ that can be used to talk
about applications in this domain”These two statements can be simplified to “Design a domain specific
‘library’ that can be used to talk about applications in this
domain”? Have you changed your mind? If so why? I still believe
these two quotes to be entirely valid.No, I don’t think I’ve changed my mind. The difference between the
above and the Java case is that domain-specific libraries are intended
for one task: you write them to provide the infrastructure in order to
write your application. The Java community seems to have a different
approach: the books and the examples of code available to developers
promote “general purpose” coding – add stuff because someone at some
point just might want it. This is the attitude that leads the the kind
of bloat we see in Java applications.Cheers
Dave
