Ilog Jrules define decision service as a ordinary web service with management capabilities using JMX MBeans. Through protocol SOAP, it's easy to invoke business rules rather than any other protocol like rmi. More information about decision services should find here.
From the view of ilog jrules, there are two types of decision services:
1) Hosted transparent decision services
2) Monitored transparent decision services
All of them drives rule execution and enables users to access Rule Execution Server through a Web service, rather than accessing it directly.
Hosted transparent decision services: Using a hosted transparent decision service, Rule Execution Server automatically exposes any deployed rule set as web services, that uses an XML schema or a Java XOM with simple types. The decision service automatically generates Web Services Description Language (WSDL) file for each deployed ruleset archive and the decision service MBean is able to retrieve execution statistics. These rulesets can be exposed as a Web service without passing through code deployment.
The hosted transparent decision service supports all primitive java type automatically. To use hosted transparent decision service, you should deploy transparent decision service archive in the same server where installed RES.
Now installed business rules with simple data type in RES will automatically exposes as web services. You can access wsdl from the rule set view of the installed business rules.
Whenever user click the link to get wsdl, component transparent decision service automatically generate the web service and a new decision service will found in the navigator.
If rule set contains custom java data types, the xom of the rule set must append to the jrules-bres-ootbds-JBOSS40.ear->jrules-bres-ootbds-JBOSS40.war\WEB-INF\lib directory and redeploy.
Through WSDL it's simple to create java proxy class to test the decision service. Most of the time, i use Xml spy editor to test soap service quickly. XML spy editor has options to create soap request and send it to the server.
Monitored transparent decision services:
Unlike a hosted transparent decision service, a monitored transparent decision service manages rulesets that use an XML schema or any Java XOM with simple types. XML parameters are represented by a String in the WSDL file.
Using the Client Project for RuleApps wizard, you can create the following projects:
1) A monitored transparent decision service project from your RuleApp project. The code generator generates two projects: the decision (or Web) service project, and the client project, which can be used to test the code generated in the decision service project. After the ruleset has been executed by this client, the transparent decision service can be monitored by the Rule Execution Server Console. Note that client generated by wizard is not well generating most of all time, it's better to generate client from the wsdl manually.
2) A Web service project from your rule project. The code generator generates a client project that can be used to test the code generated in the Web service project. This project cannot be detected by the Rule Execution Server management model, so the Rule Execution Server Console does not monitor rulesets executed by the client provided, or any other client.
Monitored transparent decision services created by RuleApps wizard execute rule set archive locally. Actually they never invoke rule set deployed in RES. So there will no execution statistics for the rule set will found in RES.
Generated decision services implements JAX-WS and only support jboss and tomcat.
Another effective way to invoke business rules are creating a web service as client to call business rules through J2EE provider. Here web service is the mediator of the business rules and client, web service encapsulate all the boilerplate code to call business rules in RES.