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14. Authoring the decisioning for the Call Center

With this lab, it is highly recommended to use DMN Runner and while you're building your model and the various custom data types to have the example right next to you. Taking advantage of the tools at hand will make your decision design much smoother and faster!

The problem statement describes a number of different inputs to our decision:

  • Call: the incoming call into the call-center

  • Employees: the employees of certain office.

  • Office: an office to which the call could potentially be routed.

Furthermore, the problem statement describes that phone numbers could be banned. So, also banned numbers can be regarded as an input to our model (although we will not implement it as an input in this lab).

With the given input, we need to make the following decisions:

  • Accept Call: the final decision we need to make is whether the given office will accept the call.
  • Can Handle Call: whether the office can actually accept the call. As defined in the problem statement, this depends on:
  • whether the phone number has been banned;
  • the purpose of the phone call (“help” or “objection”).

14.1 . Accept Call Decision Structure

  • Accept Call: the final decision we need to make is whether the given office will accept the call.

    1. Add a Decision node to the diagram by clicking on the Decision node icon and placing it in the DRD.


    2. Double-click on the node to set the name. We will name this node Accept Call.

      Accept Call Name Change

    3. With the Accept Call node selected, open the property panel. Set the Output data type to boolean.

      Output Data Type

    4. The input of this decision is the incoming call, office and employee. Create these 3 input nodes and connect them to the Accept Call decision.

      Decision and Inputs

    5. We can now set data types of our input nodes.

      1. Click on the incoming call node, open the property panel and in the Output data type section and click on the Manage button. This will open the Custom Data Types window.

        Manage Data Types

      2. In the Custom Data Types window, click on the + Add button.

        Add a custom Data Type

      3. Define the data type Phone Number as a structure and be sure to press the blue checkmark.

        Data Type Phone Number

      4. When you click the blue checkmark, a new row will open for the next type, for the first element, call it phone number with type string and then press the blue checkmark.

        Add phone number type

      5. Now to create one more item, press the plus sign in the circle that appears where the checkmark was.

        Add another data type

      6. For this data type call it country prefix with a type string. You can add a constraint to the limited values if you want, but not required, the example will use "+421" and "+420". These are more used for the forms rendering than anything else at this time. Make sure you check the blue checkmark when you're finished.

        Add country prefix

      7. Define another data type tCall as a Structure which will contain both the tPhoneNumber structure and an additional field purpose of type string:

        Data Type tCall

      8. When you’ve created the tCall type, go back to the DRD by clicking on the Editor tab.

        Call Editor Tab Change

      9. Select the incoming call node, and in the property panel, under Information item, set the node’s Output data type to tCall

        Incoming Call Data Type

    6. Next, define the following data type similar to tCall called tOffice with a field location and set it as the Output data type of the office input as such:

      Data Type Office

    7. Define the data type for employees as follows. Note that we’ve first defined the type tEmployee, and afterwards we’ve defined tEmployees as a List of tEmployee.

      Employee Type

14.2 Decision Service

With the main structure defined, we can now look at the requirements of the decision whether the office can actually accept the call. As defined in the problem statement, this depends on:

  • whether the phone number has been banned.

  • the purpose of the phone call ("help" or "objection").

We will model this decision as a DMN Decision Service that can be called by our main decision Accept Call.

  1. First, model the Decision Service in the DRD and give it the name Can Handle Call. Set it’s Output data type to boolean.

    Decision Service Can Handle Call

  2. Add a Decision Node to the Decision Service. Name it Call Can Be Handled and set it’s Output data type to boolean.

    Decision Service With Decision Node

  3. Add 2 additional Decision Nodes and name them Is Banned and Call Purpose Accepted. Both should have an Output data type of type boolean. These will be put "below the bar" on the Decision Service node, so the decisions will be evaluated, but the results will not be passed back from final service by default.

  4. Connect the 2 Decision Nodes to the Call Can Be Handled node.

    Decision Service With Decision Node

  5. The input to both the Is Banned and Call Purpose Accepted decisions is going to be a separate item called call. You will create the input node called call with data type tCall. While it will look like you're creating a separate call item here (and that is definitely how it looks), this decision service could be called independently of the whole service, which is why this call object can be used. Later in the lab, you will see how this ultimately works!

    Decision Service Call Input

  6. The Is Banned decision also needs a collection of banned phone numbers. Instead of implementing this as an Input node, we will implement this as a DMN Relation Decision.

    1. Create a new Decision Node and name it Banned Phone Numbers. Connect it to the Is Banned decision node.

      Decision Service Banned Phone Number

    2. The Ouput data type of this nodes is a new custom data type, which is a list of tPhoneNumber. We’ll name this type tPhoneNumbers, similar to how tEmployees was setup before:

      Data Type Phone Numbers

    3. Click on the Edit button of the Banned Phone Numbers node. Set the logic type of the decision to Relation. Create the following table, you will need to add one extra column and use the headers as shown of country prefix with type string and phone number with type string:

      Banned Phone Number Relation

  7. We can now implement the logic of the Is Banned decision. Click on the Edit button of the decision node. We will implement the logic as a Literal Expression. Define the following FEEL expression as below showing that we're going to take the Relational List from Banned Phone Numbers and comparing it to which is using the tCall's phone number input:

      list contains(Banned Phone Numbers, 

    Is Banned decisions

  8. The next node for which we want to implement the decision logic is Call Purpose Accepted. Click on the node, and click on the Edit button.

    Edit the Call Purpose Accepted Node

  9. Implement the following logic as a Decision Table:

    Call Purpose Accepted Decision

  10. Click on the Call Can Be Handled node and click on the node’s Edit button.

    Call Can Be Handled

  11. In the decision editor, click the Select expression to Decision Table and implement the following table:

    Can Handle Call Decision

  12. We can now implement the decision of Accept Call Decision. To do this we need to link the Decision Service to the Accept Call, to do this, you will click the outside of the Decision Service node and use the Create DMN Knowledge Requirement to connect the Decision Service to the Accept Call.

    Create DMN Knowledge Requirement between Call Can Be Handled and Accept Call

14.3 "Accept Call" Decision Logic

  1. Finally we need to Implement the Accept Call decision. This is going to be built as a Context since this can be built as a boxed expression that will have multiple steps yielding the final decision to either Accept or Deny the call!

    Create a Context Decisions

  2. With the Context now the Decision Type. The first row is going to be Call can be handled with type boolean.

    Set Context Row One Type

  3. Now we need to set the expression for the first row, this is going to be of type Invocation.

    Set invocation to a function

  4. For the invocation, we need to use it to call the Decision Service that was created.

  5. Accept Call Decision

Notice that the line 1 is the invocation of the decision service "Can Handle Call". This is an Invocation of the Can Handle Call service, passing the incoming call input as the variable call. The output of this invocation will be the boolean variable Call can be handled. This will be done using a Literal FEEL function to do this.

  1. Next create a new line with a data type Employee at the Office with data type boolean. Set the expression as another Literal expression. In this function, you will be mapping the Office locations of the employees who are working to the location of the office location. Since this is a list, you're essentially getting a collection of the employees office location and the location of the office that the call is coming from and trying to map them.

    employees[office location = office.location]
  2. After this is set, the last row, <result> can be set with a Literal expression again with the following:

    if Call can be handled then count(Employee at the Office) > 0 else false

The Call can be handled variable as then used to validate the decision result in the last line.

Final Accept Call Decision

14.4 Next steps

Next, we should deploy the project in OpenShift as a sample service.

Last update: 2023-12-21