What are the elements of decision requirement diagram?

Decision Requirement Diagrams (DRDs) are visual representations that map out the dependencies and requirements for a particular decision or set of decisions. They are a key component of Decision Model and Notation (DMN) and help in understanding how decisions are made within an organization.

The core elements modeled in Decision Requirements Diagrams (DRDs) and Decision Requirements Graphs (DRGs) are crucial for depicting the structure of decision-making processes. These elements, along with their interdependencies, define the information, knowledge, and authority needed to arrive at a decision.

Core Elements of a Decision Requirement Diagram

The fundamental elements that constitute a DRD, as referenced, include:

• Decision
• Business Knowledge Model
• Input Data
• Knowledge Source
• Decision Service

These elements work together to illustrate how a decision relies on various inputs, knowledge, and authority to reach its conclusion.

1. Decision

A Decision represents the specific outcome or choice that needs to be determined. It is the central element of the diagram, often depicted as a rectangle with clipped corners.

• Role: Defines what needs to be decided, specifying the question to be answered or the result to be achieved.
• Dependencies: A decision typically depends on Input Data, Business Knowledge Models, and other decisions.

2. Business Knowledge Model (BKM)

A Business Knowledge Model (BKM) encapsulates reusable business logic, rules, or policies. It is often represented as a rectangle with a rounded top and bottom.

• Role: Defines the knowledge that is applied to the input data to reach a decision. This can include decision tables, literal expressions, or invocations of other BKMs.
• Reusability: BKMs promote reusability of decision logic across multiple decisions or processes.

3. Input Data

Input Data represents all the information required to make a decision. This element is usually shown as a rectangle.

• Role: Provides the raw facts, figures, or conditions that a decision or Business Knowledge Model needs to process.
• Source: This data can come from various internal or external systems, databases, or user inputs.

4. Knowledge Source

A Knowledge Source represents the authoritative documents, regulations, policies, or experts that provide the basis or justification for Business Knowledge Models or decisions. It is typically depicted as a document-like shape.

• Role: Identifies the origin or reference point for the knowledge applied in a decision or BKM, ensuring compliance and traceability.
• Examples: Legislation, company policies, industry best practices, or expert opinions.

5. Decision Service

A Decision Service bundles one or more decisions and Business Knowledge Models to offer a specific decision-making capability. It is represented as a box enclosing the decisions and BKMs it provides.

• Role: Defines a reusable, executable service that provides a set of decisions, often exposed as an API for consumption by other systems or processes.
• Encapsulation: It encapsulates a complete decision-making capability, abstracting its internal complexity.

Types of Requirements Expressed

The relationships and dependencies between these elements within a DRD express three distinct kinds of requirements:

• Information Requirement: This indicates that a decision or Business Knowledge Model needs specific Input Data to function. For example, a "Credit Score Decision" requires "Applicant's Income" as Input Data.
• Knowledge Requirement: This shows that a decision uses a Business Knowledge Model for its logic. For instance, a "Loan Approval Decision" applies the "Credit Risk Assessment" BKM.
• Authority Requirement: This signifies that a Knowledge Source provides the authoritative basis or justification for a decision or a Business Knowledge Model. An example would be a "Discount Policy BKM" being authorized by the "Company Pricing Guideline" Knowledge Source.

Overview Table of DRD Elements

For a quick reference, here's a summary of the DRD elements and their roles:

By combining these elements and their dependencies, DRDs provide a clear, structured view of how decisions are made, making them indispensable for analysis, design, and automation of business decisions.