Declarative programming refers to the way the rule engine allows users to declare "what to do" as opposed to "how to do it". The key advantage of this point is that using rules can make it easy to express solutions to difficult problems and consequently have those solutions verified. Rules are much easier to read than code.

Logic and Data separation refers to the process of de-coupling logic and data components. Using this method, the logic can be spread across many domain objects or controllers and it can all be organized in one or more discrete rules files.

A kie base is a collection of rules which have been compiled by the KieBuilder. It is a repository of all the application's knowledge definitions. It may contain rules, processes, functions, and type models. The KieBase itself does not contain instance data (known as facts). Instead, sessions are created from the KieBase into which data can be inserted and where process instances may be started. It is recommended that KieBases be cached where possible to allow for repeated session creation.