Windows and Tools

We have already seen some parts of the user interface that can be used to create and maintain decision models, including the Browser window, the 'New Diagram' dialog and canvas, and the Perspective and Workspace facilities. When you select the DMN perspective Enterprise Architect loads the appropriate internal technology, effectively changing the tool into a Decision Modeling platform so that when you elect to create a new diagram you will only see the option to create a Decision Requirements diagram.

One of the most useful aspects of Enterprise Architect's implementation of the DMN standard is the ability to simulate Decision Models. This means that a Requirements Analyst or other stakeholder can perform trial executions of the model using test data to simulate what output a Decision Model would generate in a particular context. So, for example, in our Fraud Detection model a number of inputs to the Decision Model could be provided, and an output would be produced based on this input and the rules that had been configured.

Enterprise Architect provides two important windows for working with decisions; we will introduce both of these windows now and, as you will see throughout the Guidebook, these windows will be used extensively.

• The DMN Expression Window - used to define the expression in the form of Decision Tables, boxed expressions and other expression types
• The DMN Simulation Window - used to configure and run simulations

In addition there is a wide range of tools that can be used to facilitate working with Decision Models; we will have a look at some of these later in the Guidebook. These additional tools include:

• Document Generation
• Discussion and Reviews
• Traceability
• Relationship Matrices
• Diagram Filters
• Specification Manager

DMN Expression Window

We have spent a lot of time introducing the DMN and describing the context for the models including the location in the Browser window and adding diagram elements. The expression window is the engine room or control center for the decisions and it is where the logic resides that effectively converts input information into a decision output based on the user defined expressions, which could for example be rules defined in a decision table. There is a validation facility that allows the rules defined in Decision Tables to be tested for correctness and coverage. It is also where input data is defined including Data Sets that can be created and reused to run the simulation using pre-defined input data allowing testing to be performed in a robust and repeatable way.

Simulate Ribbon

The Simulate ribbon provides a selection of tools for working with simulations, so here we see the Decision Modeling Simulation facility keep company with a number of other simulation tools, including Business Process Simulation (BPSim), Modelica/Simulink (SysML Pararametric) and StateMachine Simulation.

The DMN item on the ribbon has a drop-down menu that provides a number of facilities for working with Decision Modeling simulations. These include selecting a workspace and perspective and finding configuration items that represent model fragments with simulations that have already been configured.

The ribbon provides a generic control panel for running simulations of any kind; this can be used when a DMN simulation has been configured and loaded. It allows simulations to be run to completion, paused, stepped through or stopped. This facility will be your friend as you develop Decision Models, or evaluate existing ones and need to understand what parts of the model have contributed to the final output. We will look at running simulations in more detail later in the Guidebook.

DMN Simulation Window

The Simulation window provides the facilities to configure and run the simulation including selecting what Data Sets should be used with each decision. The result of the simulation will be displayed in the current diagram in the form of annotations to the diagram elements. The simulation can also be controlled from the Run Simulation Panel of the Simulate Ribbon and both control panels allow the simulation to be stepped through showing which rules in the decision expressions (including decision tables) are selected for the given input data. The simulation windows will become active when a Simulation Configuration is loaded and this can be achieved by double clicking the Configuration element in the current diagram.

The second diagram demonstrates the annotations to a diagram that are created when a simulation is run. The elements have the inputs and outputs annotated for each level of the decision graph and these can be seen to be bubbling up from the lower decisions in the hierarchy, up to the highest decision (the one that has only incoming but does not have any outgoing information requirements).

Other Tools

In the previous sections we have introduced you to the main windows used when working with the Decision Models, and in the topic before this one we introduced the main diagram used with Decision modeling, namely the Decision Requirements diagram. There is, however, a wide range of other tools that will be invaluable when creating and managing these models, which will be introduced later in the document. We introduced the Browser window when discussing setting up a repository structure but we haven't yet introduced the other tabs or views of the repository, which are useful to get a focused or 'keyhole' view of the part of the decision model that you are working on.

• Context Browser - provides a focused subset of the elements in the project browser
• Diagram Browser - provides a list of the elements and connectors on the current diagram
• Details display (Inspector window) - provides a list of the important features, properties and relationships of the current element