Create Contexts

A context is a collection of one or more key-value pairs with an optional result field. Each pair is called a context entry. The key attribute within a context entry acts as an identifier to its corresponding value attribute.

You can use a context to collectively document all decision logic related to a particular scenario or entity. Say you need to determine the loan eligibility of an applicant, based on the applicant’s net monthly income and expense. For this purpose, you can create a decision named Loan Eligibility using the Context notation and add expressions or logic for gross monthly income, monthly expense, and net monthly income. Then, you can add a result field (within the context) that evaluates the net income and expense for loan eligibility. The result field can be a boxed expression that contains logic using the keys specified in the context.

To create a decision with the Context notation:

1. Add a new decision element to the model.
   1. On the Diagram palette, under Decisions select Context, and drag it onto the canvas.
   2. Double-click the element to edit its logic. You can also edit the context's logic from the Decision Properties pane; click the three dots on the element, then select Edit to open the Decision Properties pane. In the Decision Properties pane, click Edit next to the Name field.
   An empty Context is created.
2. Click Add entry to create a new context entry. A key-value pair is created with the expression notation selected by default in the Value field.
3. To change the logical notation for an entry, click Change Value in the Key field to open the Change Value menu. Select a different notation from the available options.
4. In the Key field of a context entry, enter a unique name.
5. In the corresponding Value field, configure the logic for the selected notation. You can use input variables or built-in functions to define the logic.
6. Repeat steps 2 to 5 to add another entry into the context.
7. Drag and drop context entries to reorder them within the context.
8. Changes you make within the decision model are automatically saved and validated from time to time. Errors and warnings, if any, are displayed within the decision panel.

Note:

If you add a function as one of the context entries, the context as a whole doesn’t return a result. However, you will still be able to invoke results of individual context entries throughout the decision model.

The following image shows a context with a result field that determines the total income of applicants:

Description of the illustration dmn-context-loan-eligibility.png

The output of the result field is the context’s output. In this case, the context returns the result of the boxed expression. You can reference the context’s result in other decisions within the model using the context name (for example, Total Income).

The following image shows contexts with and without a result field, and a boxed expression referencing a context and a context entry to determine the loan eligibility of applicants:

Description of the illustration dmn-context-loaneligibility.png

The output of this context returns a true or false decision that is based on evaluating the contexts. To reference a particular context entry from another decision, use the format ContextName.EntryKey (for example, Income.Salary). Within a context, an entry can only reference entries that are above it.