The Drools execution server is a web application that allows us to execute rules remotely. The server is accessible through a REST-like interface (REST stands for Representational State Transfer—http://en.wikipedia.org/wiki/Representational_State_Transfer). Thanks to REST, we can build very lightweight clients that don't need any Drools libraries for rule execution (not even a JVM). To demonstrate this, we'll build a client using Ruby language.

Drools server can be found in the standard Drools binary distribution within the web application module drools-server.war. The Drools web server application needs to be deployed to an application server and started. It uses multiple knowledge agents to cache KnowledgeBase instances. Configuration for these knowledge agents is provided during startup through property files.