Invocation

  This icon in the top right corner of the Decision or Business Knowledge Model (BKM) element indicates that it is implemented as an Invocation. The Invocation expression type is the mechanism by which decision expressions can be accessed and reused in different contexts. You will recall in an earlier topic we discussed the Decision Modeling notation and introduced the Business Knowledge Model (BKM) as a method of reusing predefined decision logic. The invocation expression type is the method that is used to access the decision logic in a BKM, providing values that are passed through to a BKM or Decision Service's parameters and in turn receiving the output. The invocation can be applied to both Decision elements and BKM elements, both of which would invoke a Business Knowledge Model or a Decision Service.

An invocation is a container for the parameter bindings that provide the context for the evaluation of the body of a Business Knowledge Model. There are two common use cases for an Invocation:

• Used to bind Input Data to a Business Knowledge Model
• Used to bind parameters or context entry variables to a Business Knowledge Model

An invocation is a tabular representation of how decision logic that is defined within an invocable element (a Business Knowledge Model or a Decision Service) is invoked by a decision or by another Business Knowledge Model.

When an Invocation is selected, the layout of features accessible in the DMN Expression window is:

For more details refer to the Toolbar for Invocation Editor Help topic.

The parameter bindings of an Invocation provide the context for evaluation of the body of the invocable element.

In this example:

• Decision 'Post-bureau risk category' is represented as an invocation connecting to Business Knowledge Model 'Post-bureau risk category table', implemented as a Decision Table
• Decision 'Post-bureau risk category' is the target of three information requirement connectors from two input data and one decision
• The binding list binds the input values to the Business Knowledge Model's parameters
• The invocation also specified the requested 'OutputClause'; in the case where a Decision Table has multiple Output Clauses defined, the invocation must explicitly request an Output Clause as the result of the expression

Inputs from other Decisions and InputData elements can be set by pressing the Spacebar in the field.

As an Invocation can only invoke one Business Knowledge Model the output is defined by the Business Knowledge Model output.