Sometimes a decision service needs to consider information or context from previous invocations of the service. For example, you might want to award a customer discount if they purchased more than two items in one week. The information you keep about each invocation is called the state, and a decision service that uses state in its business logic is stateful. Nigel Crowther, our presenter at DecisionCAMP-2017, wrote an article that discusses three ways you can build stateful decision services with IBM ODM.