Drools Interview Questions

Drool is a Business Rule Management System that is produced and distributed by the JBoss Community. Drool is mainly used by a different organization with an attempt to implement complex applications using automatic patterns based on various business rules. This framework is primarily constructed on the extension provided by the Rete pattern – matching algorithm.

Other programming languages work on a certain set pattern and do not offer many modifications to be applied for the coding. In addition to that, conventional programming languages do not provide management solutions for various business, which is the main feature of Drools. For instance, considering the example of the owner of the jewelry shop.

If he needs to calculate the amount of discount to be provided to customers on the basis of the type of jewelry that is most sold, then he will not be able to make such predictions using basic programming languages. However, with the help of Drool, which is a Business Rule Management Tool, discounts can be daily changed without the need for expertise.

Some of the essential components of the JBoss enterprise include:

• JBoss enterprise web – platform: It is a software architecture that mainly supports and runs various business rule management system components
• JBoss enterprise application – platform: It is another software architecture that is also used to support and run various business rule management system
• Business Rules Engine – It is a centralized repository that contains all the basic Drools knowledge that can be used to run, edit and manage multitudes of business rules
• Business Rules Repository

The following simple coding can help print out any information required about the September holidays:

rule “validate holiday”
dialect “mvel”
dialect “java”
when
	$h1 : Holiday (month == “September”)
then
System.out.println ($h1.name + “:” + $h1.month);
end

KIE is an acronym for “Knowledge is everything”. The latest versions of Drools have an approach that is used to create different knowledge bases and sessions. These bases act as an interface between the one that manages the set and of rules and the one that processes. One of the main objectives of KIE is to store the various knowledge bases and reuse the rules whenever required. This is mainly carried out because making a new set of rules on repetition can be expensive and time-consuming.

In “backward chaining”, one must first make a choice and after that check if the choice is valid or not by backtracking through a succession of occasions. For instance in the event that one needs to see whether a specific student has passed the exam or not? At that point, I will take the choice that the student has passed. Then dissect the information by backtracking through the succession of investigation of information. In like manner the decision made is either right or wrong. In light of necessity, both of the two methodologies can be utilized. Sometimes the blend of both forward and backward chaining is additionally utilized. In backward chaining, it is regularly alluded to as induction inquiries and Drools implement it with constructive questions.

Some of the commonly used execution control statements used in Drools include:

• Rule flow group: It is generally utilized for rules from the JBoss business project management process
• Agenda – group: It is an optional keyword that is assigned to all the rules available in the database
• Activation – group: It is a reserved keyword found in all Drools DRL files. Activation – the group can consist of either a single rule or multiple rules. The rules in this group are run using “if…else if...else” statements

Decision Tables used in Drools are based on excel decision tables. One of the greatest advantages of using Drools Decision Table is that even a non – technical individual can change the logic applied. However, if one is looking to modify the .drl files then he might require help from a profession with adequate technical knowledge. As the usage with .drl files become more complicated, then there is a requirement of a higher professional such as a Business Analyst to find solutions to the problem. In addition, making frequent alterations to the .drl files is nothing less than a herculean task and here decision tables come very handily even for non – programmers.

Some of the advantages of using rule engines in business project management include:

• High flexibility: keeping your guidelines into a Knowledgebase let you adjust effectively your choices when they are evolving.
• Easy to learn: Rules are simpler to comprehend than procedural code so they can be successfully used to bridge any hindrance between business expert and engineers.
• Reduced intricacy: When installing bunches of decisions, it mainly focuses on your procedural codes that it can undoubtedly transform your application into a bad dream. Also, the rules can handle much better expanding multifaceted nature since they utilize a predictable portrayal of business rules.
• Reusability: Keeping rules at one spot prompts more noteworthy reusability of your business rules. Likewise, conventional procedural code regularly forces pointless varieties of base guidelines, which are consequently increasingly hard to reuse in different settings.

Drools Process (also known as Drools Flow) is a framework that provides a flow of work in addition to various business processes.

A global variable is a keyword for Drools. “Global” is the variable that is used in Drools which is visible to all the rules inside .drl files. The main objective of using a global variable is that it can be utilized for any kind of object without worrying about mismatches.

Accumulate is an extra element introduced in the recent versions of Drools that is used to iterate the list of objects and also help in the authentication of data in operations utilizing Java. For instance: accumulate (Counter() ; $cnt : count())

The symbol “$” is used before variables in Drools to make sure that there is a difference between variables of Rules and the POJO class.

Drools Planner, also known as automated planning is used to optimize the process that takes during the NP-hard planning issues.

The two types of interfaces in knowledge sessions are:

• Stateless Knowledge Session
• Stateful Knowledge Session