drools declare

Drools Declare is a keyword used in the Drools rule engine to define global variables and declare facts. It allows you to define data structures and declare them as facts that can be used in the rules.

In Drools, you can use the Declare keyword to define global variables, declare new data types, and create facts. The Declare statement is usually placed at the beginning of the rule file or in a separate file containing only declarations.

For example, you can use the Declare keyword to define a new data type called "Person" with attributes like name, age, and address. Once declared, you can create instances of this data type and use them as facts in your rules.

Here's an example of how you can use the Declare keyword in Drools:

declare Person
    name: String
    age: int
    address: String
end

rule "Example Rule"
    when
        $person: Person(name == "John")
    then
        // Rule actions here
end

In this example, we declare a new data type called "Person" with attributes name, age, and address. Then, we define a rule that matches instances of Person with the name "John". When this rule is triggered, you can perform actions based on the matched Person object.

Drools Declare provides a way to define data structures and declare them as facts, allowing you to reason about and manipulate data within your rule engine.