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Top 25 Drools Interview Question & Answers updated 2022

1.Drools Characteristics

Criteria : Result
Functionality : Business rules management & reasoning engine
Scope : Can be used for local decisions or large scale decisions

2.What is Drool?

Drool is one of the business rule management systems or BRMS that has forward and backward chaining inference-based rule engines.

3.What is another nomenclature for Drool?

Drool is also known as a production rule system that uses an enhanced implementation of the Rete algorithm.

4.What is meant by Knowledge is Everything or KIE?

KIE is the new umbrella name to the systems set like drools, jBPM, optaPlanner, Guvnor, and uberFire and such other technologies.

5.What is the standard supported by Drool?

Drool supports JSR-94 standards for the business rule engine. It also supports enterprise frameworks for construction, enforcement, as well as maintenance of business policies.

6.What is JBoss Enterprise BRMS?

JBoss Enterprise BRMS is the reasoning engine for policy and rule developments for business. It also manages access and changes.

7.What is the productized version of Drools?

JBoss Enterprise BRMS is the productized version of Drools and it has enterprise level support.

8.What are the components of JBoss Enterprise Version?

The components of JBoss Enterprise Version are JBoss Enterprise web platform, JBoss Enterprise application of SOA platform, Business Rules Engine, and Business Rules Manager.

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9.What are the features of JBoss Enterprise Web Platform?

The JBoss Enterprise Web Platform is the software infrastructure that supports the running of BRMS components.

10.What are the features of JBoss Enterprise Application or SOA Platform?

It is the application software structure in the system that supports running of BRMS components.

11.Who uses the Business Rules Engine?

Drools experts use the Business Rules Engine through the Rete algorithm and Drools Rule Language (DLR).

12.What is a Business Rules Manager?

Business Rules Manager is a centralized repository for the Drools knowledge bases and has a rich web-based Graphical User Interface as well as tools and editors to manage large numbers of rules.

13.What is meant by Drools Guvnor and Drools Expert?

Drools Guvnor is the Business Rules Manager and Drools Expert is the Business Rules Engine.

14.What is Drools Flow?

Drools Flow or process or workflow as it is called, provides the workflow as well as business processes.

15.What is the tool for managing complex event processing in Drools?

It is the Drools Fusion that is used for event processing as well as temporal reasoning.

16.What is meant by Drools Planner?

Drools Planner or automated planning optimizes the process including the NP-hard planning problems.

17.What is the purpose of the dialect in Drools?

Dialect or mve1 points to the Getter and Setters of the variables of plain old Java objects (POJO). Dialect “java” is used for writing Java code in the rules.

18.What is the restriction in using Java code?

Users cannot use Java code inside the “when” part of the rules. However, it can be used in the “then” part.

19.What is the reason for putting the $ symbol before the variables?

The objective of putting the $ symbol before the variables is to ensure the difference between variables of POJO classes and Rules.

20.What is provided by Drools?

Drools provides the core Business Rules Engine (BRE) and Web Authoring and Rules Management Application (Drools Workbench) as well as the Eclipse IDE plugin for core developments.

21.What are Drool Workbench, Expert, and Fusion?

Drools Workbench is the web user interface for authoring and management. Drools Expert is the business rule engine and Drools Fusion is the complex event processing feature.

22.How to halt a process in a DRL file?

User has to resort to drools.halt() in the consequence (then) part of the application.

23.How to remove an object from a knowledge session?

Using the retract method to remove the object from a knowledge session can help.

24.How to fetch and play around with the rules in java code?

Rules do not exist as Java codes. However it is possible to use Guvnor REST API for downloading the DRL source code for the rules and thereafter upload them all over again.

25.Is it possible using round trips between rules modified in Guvnor, loade in the UI, modified and uploaded to Guvnor?

There is no such way of ensuring this. Especially newcomers should not try this to avoid complications.

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