Variable types

You can define a Decision service variable by first specifying the name of the variable, then setting the variable type. The variable value can be a simple data type such as a string, integer, or date. You can also define a complex variable type using a business object that contains parameters.

Declaring the variables for a service enables the service to display and manipulate the values that it receives from (input) and then pushes back up (output) to the main business process.

Important: You must initialize complex variable structures before running the Decision service. In IBM® BPM, all complex variables and all lists (arrays) must be initialized before you use them in a business process definition or service. If you do not initialize a complex variable or list, you may receive runtime errors or notice that the controls to which the variables are bound do not behave as expected. For more information, refer to the related topic "Initializing complex variables and lists."

Complex variables for hierarchical data

In IBM Business Process Manager, you can create a custom variable type by using a base variable type or by defining a new complex structure. You can create rules about complex data that is nested, or hierarchical. Data that is referenced within the text of a rule is not limited to simple data types such as string, integer, or date. You can create complicated rules with nested variable structure. For example, in the Decision service shown in the following diagram, the variable paymentIn has the variable type Payment, and contains other, nested variables.

Rule variables panel showing a nested complex variable type

For more information about creating complex, hierarchical variable types, see the related topic "Adding process variables to a BPD."

There are several complex variable types that are not supported when authoring rules in a Decision service. The unsupported variable types are:

SQLResult
XMLDocument
XMLElement
XMLNodeList

Collections (lists) of variables

You can write rules against collections, or lists of variables, using Business Action Language (BAL) rule constructs. You can use a variable to retrieve a collection (list) of objects of a specific type. Use a list parameter in a business object when then are numerous objects that your rule must run against, instead of just a single object. For example, if you are writing a rule about an invoice, and there are multiple line items in the invoice, then the invoice is actually a collection of line items. To write a rule against the number of line items (if there are 10 or more line items, then process this invoice manually), add a list parameter in a complex variable to your rule.

In the complex variable type, or business object, shown in the following diagram, PastPayment is a list parameter, which means that it contains multiple objects of the String, Decimal and Date variable type. To identify a variable as a collection or list, click to select the Is List option under Parameter Properties.

Complex variable type (business object) with a collection (list) parameter defined.

Predefined variable types

Many pre-defined variable types are provided by the IBM BPM System Data toolkit. These variables are defined as business objects. You can open a business object in Process Designer and review the Documentation field to learn when and how to use each variable type. For example, to open the Record business object included in the System Data toolkit, complete these steps:

Open a process application in Process Designer.
Click the indicator next to the Toolkits category to see a list of toolkit dependencies for the current process application.
Click the indicator next to the System Data toolkit to see its contents.
Click the Data category
Double-click the Record business object to open it. The Documentation field provides information about the business object. The documentation informs you that a Record is a group of ANY typed variables and that you do not need to declare the number of ANY typed variables that you want to go into the Record. So, the Record object is similar to a Structure object, except you do not need to declare the type or the number of variables it contains.

For additional information about using variable types in rules, refer to the related topic "Types of variable definition" in the WebSphere ILOG JRules InfoCenter.