This post about the symbiosis between process modelling and decision modelling is the last in a series on business processes: from building a robust process architecture, via scoping a process, to accurately modelling and simulating a business process.

This post about the symbiosis between process modelling and decision modelling is the last in a series on business processes: from building a robust process architecture, via scoping a process, to accurately modelling and simulating a business process.

As a reference, I have listed the respective blog posts below:

To complete the series, I want to highlight the importance and the key benefits of decision modelling in combination with process modelling in this post.


BPMN – the process modelling standard

Business Process Model & Notation (BPMN) is ‘de facto’ standard for process modelling. Almost everyone doing process modelling is using BPMN. It is a set of guidelines to map process flows and is common knowledge to process practitioners. However, often you see entangled, spaghetti process flows, where process logic is interwoven with decision logic.

This results in extremely difficult to understand and hard to maintain process models.  A change to any of the business rules requires a lot of rework, even re-design of a process flow. Moreover, the decision logic is usually inaccurate and incomplete. Instead of capturing decision logic in the process model, a decision model can capture this logic precisely in a separate, but linked model.

Below an example of a relatively straightforward cab booking process diagram using the BPMN standard.


DMN – the decision modelling standard

Decision Model & Notation (DMN) is a relatively new Object Management Group (OMG) standard design to fill the gap within BPMN. DMN provides an industry standard modelling notation for decisions that are graphical and readily understandable to business users. However, it is still a far less established standard than BPMN is for process modelling. With DMN, organisations have a standardised way to model and maintain decisions and their business rules logic.

In the context of DMN, a decision is an act of determining an output value, based on a number of input values, using decision logic defining how the output is determined from the inputs. A decision model is a formal model of an area of decision-making, expressed as decision requirements and decision logic.

A decision model is defined in two levels, the Decision Requirements Level and the Decision Logic Level. The Decision Requirements Level is the more abstract level of modelling, made up of a Decision Requirements Graph (DRG) represented in one or more Decision Requirements Diagrams (DRD). It defines the decisions to be made, the interrelationships, and the required components of the decision logic. the Decision Logic Level is the detailed level of modelling, consisting of the value expressions associated with decisions and business knowledge models. In other words, the required decisions are captured in some form of logic expression with sufficient detail enabling validation and/or automation.

The figure below depicts clearly how a decision model (DMN), and the decision logic connect to a process model (BPMN).

In summary, it comes down to the following:

  • a process step (i.e. Decide routing) links to a decision (i.e. Routing);
  • a decision (i.e. Routing) links to business knowledge (i.e. Eligibility);
  • a business knowledge (i.e. Eligibility) links to a value expression e.g. a decision table of Eligibility rules.

Typically, the decision logic level maps to the process execution domain where processes are implemented.


Simplifying processes with decision modelling

Decision modelling can simplify processes dramatically through separating gateways into different type of diagrams and as such, reducing greatly the number of shapes and links of the process flow.  Consequently, when and where decision making is required on a process model, it is represented using a ‘business rules’ task which is linked to a ‘decision model’.

The model on the left presents an overly complex process (the ‘before‘ state) compared to a simplified process model using decision modelling techniques (the ‘after‘ state) on the right. The result is a dramatic simplification of the process flow.


Benefits of using both BPMN and DMN standards

James Taylor and Tom Debevoise identified four key benefits of using the two standards together:

Streamlined processes

A combination of process modelling and decision modelling produces simpler business processes by eliminating unnecessary gateways and scripting activities. Instead of capturing decision logic in the process model, decision modelling captures this logic precisely in a separate but linked model. Consequently, separating business or decision logic from the process logic dramatically simplifies process flows.

Focused discovery

By focusing on decisions and processes independently the discovery process is more focused. Different stakeholders are involved in the process and the decisions within it, so separate models often work better. Because the pair of models are each simpler than a single combined model, the discovery and modelling activities are easier to manage and complete successfully. Decision models link the tasks in a process to the business rules that will be required as well as to the organisations and business metrics that matter. All this makes the discovery process more effective.

Improved visibility and flexibility

DMN structures and manages the business rules that a process requires, gathering them into a coherent model at each decision point in the process. This makes it easier to find the right rules to change and allows the rules (decision) to be changed independently of the process improving flexibility. Because the decision models are linked to business metrics too, organisations get visibility into how their rules impact their business performance through the model.

Greater analytic agility

DMN provides a model of the decision making in a process and this allows the impact of analytic models to be clearly expressed, allowing increasingly advanced analytics to be integrated into a process.



Together, BPMN and DMN, may be used to more efficiently build process models. The two standards are seen as mutually reinforcing each other. This way, organisations can unleash the full potential of their process initiatives.


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About the author:

About the author:

Bart Nijs

Bart is an international professional with 10+ years of experience of business change using a variety of business modelling techniques to produce coherent architectural models.Bart gained a wealth of enterprise modelling experience working in many organisations and sectors across Europe and the EMEA region assisting in tool implementation and modelling.

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