A package is a collection of rules and other related constructs, such as imports and globals. The package members are typically related to each other - perhaps HR rules, for instance. A package represents a namespace, which ideally is kept unique for a given grouping of rules. The package name itself is the namespace, and is not related to files or folders in any way.

It is possible to assemble rules from multiple rule sources, and have one top level package configuration that all the rules are kept under (when the rules are assembled). Although, it is not possible to merge into the same package resources declared under different names. A single Rulebase, can though, contain multiple packages built on it. A common structure, is to have all the rules for a package in the same file as the package declaration (so that is it entirely self contained).

The following rail road diagram shows all the components that may make up a package. Note that a package MUST have a namespace and be declared using standard java conventions for package names; i.e. no spaces, unlike rule names which allow spaces. In terms of the order of elements, they can appear in any order in the rule file, with the exception of the "package" and "expander" statements being at the top of the file, before any rules appear. In all cases, the semi colons are optional.

Figure 5.3. package

5.3.1. import

Figure 5.4. import

Import statements work like import statements in Java. You need to specify the fully qualified paths and type names for any objects you want to use in the rules. Drools automatically imports classes from the same named java package and from the java.lang package.