IDD (Interface Design Document)

An Interface Design Document (IDD) is a structured specification detailing how an interface between two or more systems should be designed. It serves as a blueprint for the development, testing, and implementation of integrations in ERP platforms, CRM systems, cloud solutions, and other IT environments where systems need to exchange information reliably and consistently. IDD is a key artifact within integration architecture.

An IDD typically includes:

• Purpose: Why the interface is needed and which business process it supports.

• Data model: Structure of exchanged data, including fields, formats, and validation rules.

• Message flows: Direction, frequency, and triggers for communication.

• Protocols and formats: Such as HTTP, REST, SOAP, XML, JSON, or Flat File.

• Error handling: Rules for retries, error codes, and logging.

• Security: Authentication, authorisation, and encryption.

• Non-functional requirements: Performance, scalability, durability, and reliability.

IDDs emerged in the era of early integration work, when EDI, database exchange, and industry-specific protocols required detailed documentation. With the rise of SOA, API design, and cloud computing, IDDs became even more important for ensuring standardised and maintainable interfaces.

IDDs are widely used for integrations involving Dynamics 365, Business Central, Azure Integration Services, Power Platform, and external APIs. They form the basis for development using Azure Functions, Logic Apps, API Management, and data structures in Dataverse, supporting governance and quality throughout the integration lifecycle.

An IDD defines how an interface should be constructed, secured, and maintained. By providing clear technical and functional specifications, it supports robust and scalable integration solutions.