James Taylor's Decision Management

A self-contained, callable service with a view of all the conditions and actions that need to be considered to make an operational business decision

Or, more simply

A service that answers a business question for other services

Such a service has some additional characteristics over and above a typical service:

• Behavior understandable to the business
  After all we are talking about a "business decision" here so the business had better be able to verify exactly what is going on inside
• Supports rapid iteration without disruption
  Business decisions change all the time so a decision service has to be both flexible and designed for this change
• Integrates historical data
  Business decisions are increasingly made "by the numbers" with much reference to historical data. Decision Services need a similar ability to use historical data, and trends/insight extrapolated from it.
• Expects multi-channel use
  While this is largely covered by the standard items it is worth noting as it means that VERY different kinds of applications will use the service - everything from ATMs and SmartPhones to Call Center applications and Bill Printing.
• Manages exceptions well
  Not only should it respond sensibly when it cannot decide, it should ensure that enough context is returned as to why it could not decide to assist a manual process
• Must explain its execution
  Many decisions must demonstrate compliance or conformance with policy. Any decision service must be able to log exactly how it decided and that information must be accessible to non-technical users