Another principle today.

In the realm of software development, the four-eyes principle dictates that an action can only be executed when it is approved by two individuals, each providing a unique perspective and oversight. This principle is designed to safeguard against errors and misuse, ensuring the integrity and quality of the software.

The four eyes principle can help during the construction of software systems by finding weaknesses in architecture, design or code and can help to improve the quality. In every phase of the software development cycle, this principle can be applied, from the requirements analysis phase to the detailed coding phase.

Software architecture, design, and code could be co-developed by two people or peer-reviewed.

In the design of software systems, the four-eye principle applies to the process of validating design decisions on various levels. Pair programming is a software development technique in which two programmers work together on code, one usually doing the coding and the other doing the validation. In other engineering industries, dual or duplicate inspection is a common practice.

In regulated environments such as Financial Institutions, compliance requirements may dictate that code is always peer-reviewed to prevent backdoors in code.

In software systems itself, the four-eyes principles may be implemented when supporting business processes requiring this for security or quality validation reasons.

Change management, a critical aspect of software development, often relies on the four-eyes principle. When code changes are transitioned into production, a formal change board may mandate a signed-off peer review, ensuring that all changes meet the required standards. Change and Configuration Management tools for software systems are often designed to support this four-eyes principle process, further enhancing the quality and security of the production environment.

Further assurance can be added by adding a (random) rotation scheme of authorized individuals to serve as the second pair of eyes. This may provide additional assurance as it will not be known beforehand which two individuals will be dealing with a given decision.

Related / similar: Dual Inspection, Code Review.