The XOM (Execution Object Model) and BOM (Business Object Model) are key artifacts of our Rule project. The execution object model (XOM) is the model against which you run rules, it references the application objects and data, and is the base implementation of the business object model (BOM). For more information about XOM/BOM visit the IBM Knowledge Center here.
We can generate our BOM entries from a XOM (Java or XSD) and get the objects we will verbalize for our rules. A very common requirement in a project is to work with Lists and return a populated List with values from a Rule Action or Decision Table. You will notice that after you create your BOM entry from an XOM with Lists (maxOccurs=”unbounded”) you will get an object of type java.util.Vector but with no direct relationship between the elements. Please review the following problem example and a workaround on how to fix it and implement Lists correctly.
Let’s say you have an XSD with an element like this:
<element name=”recruits” type=”tns:Recruit” maxOccurs=”unbounded” minOccurs=”0″></element>
After you create the BOM entry, you will get an object like this:
With no proper verbalization and without a way to use it in a Rule Action, Decision Table or Decision Tree correctly. In this example we want to add objects of type Recruit to our RecruitsList and display this list in the output of our Decision Service. Follow the steps below to implement a workaround and accomplish our goal.
- Creating a new Method member
- Let’s remove this verbalization and navigate to the Class tab.
- We are going to create a new method to add our Objects. Click “New…” in the Members section.
- Select “Method”, give a proper Name and “void” for Type.
- Now add Arguments according to the Object you are going to add to your list, in our example the Recruit’s attributes. At the end you should have something like this:
- Tip: Remember that the types have to match, if you are using a virtual value assign the corresponding type like the example. For more information about dynamic domains and virtual values read my previous post here.
- Now we need to create a proper verbalization for our new method and implement the BOM to XOM Mapping logic.
- Navigate to the Member Verbalization section and click “Create”. Modify the Action phrase according to your Object. In this sample:
- The last and most important step is to define our BOM to XOM Mapping logic. We need to map our method arguments with the attributes of our Object, in this sample with the Recruit’s age, country, name and sex:Tip: Don’t forget to initialize the response list variable in your ruleflow or variableSet.
Now we are ready to use our method in any Rule and return a list structure schema in our Decision Service response!
Decision Table demonstration sample:
After we test our rules we will see this list structure in the response (Testing with SoapUI):
Please feel free to comment or contact me with any doubts or feedback. Thank you!