Visualization Tool for the Rego Language Used in Policy as Code and Its Use Cases

Policy as Code refers to efforts to describe and implement policies in a machine-readable format within system development. One example is Open Policy Agent (OPA), which uses a declarative language called Rego to define policies concisely. However, Rego's declarative syntax can be difficult for developers accustomed to procedural programming and those unfamiliar with coding, making the adoption of OPA more challenging. In this research, we propose two methods-evaluation tree and evaluation step analysis-to visualize policies written in Rego. These methods adapt techniques such as call trees and time-travel debugging, typically used in procedural languages, to the declarative structure of Rego. We implemented these methods as a web tool to make Rego policies more accessible. Our findings show that this tool helps users unfamiliar with Rego better understand policies.