Using the Decision Table Operator

  Decision tables provide a way to express a complex set of business rules as a table of conditions that apply to incoming tuple fields, with one or more specified actions for each row of conditions. By default, all rows of the table are evaluated against each incoming tuple, with an option to stop evaluation at the first matching row.

Each row can be thought of as a single rule in a table made up of many rules. The individual rules are often straightforward. When built into an EventFlow application, the Decision Table operator allows you to to author, test, and publish decision tables.

The Decision Table operator processes tuples on its input port. For each tuple, it evaluates the conditions of the currently-loaded rules, and emits an action tuple for each matching rule. A rule matches if all its conditions evaluate to true in the context of the input tuple. If the operator's Single Row Execution property is selected, a single tuple is emitted for the first matching rule.

Emitted tuples contain a copy of the input tuple, an action tuple derived from the rule's action columns, and a copy of the matching rules. Rules can be assigned priorities to determine which rule fires when the conditions of multiple rules match the input tuple.

For further information about decision tables in general, see Using Decision Tables.

Name: Use this required field to specify or change the name of this instance of this component, which must be unique in the current EventFlow module. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Enable Error Output Port: Select this check box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports to learn about Error Ports.

Description: Optionally enter text to briefly describe the component's purpose and function. In the EventFlow Editor canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

Use the Decision Table Settings tab to specify the decision table file to load, and, if available, the domain model file to load, when this decision table operator starts. This table also configures the operator's logging level, and provides a schema grid in which to set the schema of the action tuple emitted as part of the operator's output tuple.

Action Schema: Use this property to configure the schema of the action tuple emitted as one of the fields of the operator's outgoing tuple. The action tuple must contain one field to match each action column in your decision table. Action schema fields not present in the decision table get populated with nulls.

Use the Concurrency tab to specify the use of parallel regions for this instance of this component. Consider selecting the parallel regions check box if this component instance is long-running or compute-intensive, can run without data dependencies on other StreamBase components, and would not cause the containing module to block while waiting for a thread to return. In this case, you may be able to improve performance by selecting this option. This option directs StreamBase Server to process this component concurrently with other processing in the application. The operating systems supported by StreamBase automatically distribute the processing of threads across multiple processors.

The Decision Table operator has the following ports:

In addition to standard ports, the operator exposes the following streams when the operator is running. The CanvasName component of both stream names is the case-sensitive name of the operator on the EventFlow Editor's canvas. Thus, for an operator named DT1, you would have streams DT1.Control and DT1.Status.

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