Decision Modelling

Definition

Decision Modelling is used to represent how a repeatable business decision is made by separating decision logic from processes and making it explicit and manageable. It provides a clear, unambiguous way to show the inputs, logic, and outcomes of a decision. The Decision Model and Notation (DMN) standard provides a graphical language for decision modelling, and decision tables are the most common tool for capturing the logic inside a decision node.

Inputs

• Business rules and policies governing the decision
• Identified inputs (data elements) required to make the decision
• Subject matter experts who own the decision logic
• Existing process models that reference the decision point

Outputs

• Decision model diagram showing decision nodes, input data, and knowledge requirements
• Decision tables capturing the combinations of conditions and resulting actions
• Documented decision logic that can be validated by business owners and implemented by IT
• Inputs to business rules management, automation, and system design

When to Use

• Clarifying complex business logic that varies by multiple conditions
• Enabling automation of repeatable decisions (eligibility, pricing, classification, compliance)
• Managing business rules independently from processes so they can be updated without code changes
• Ensuring consistency and transparency in decision-making across teams and systems

When Not to Use

• When decisions are fully discretionary and cannot be reduced to rules
• When the decision is simple enough to describe in a single business rule
• When the audience is not ready for formal modelling notation — use plain-language decision tables first