Code Review Process Class Diagram Template

A class diagram for the code review process models the key entities, attributes, and relationships involved as a pull request moves from creation through final merge. This template typically captures classes such as PullRequest, Reviewer, Author, Comment, Approval, and Repository, along with their properties and the associations between them — for example, a PullRequest aggregates many Comments, requires one or more Approvals, and is owned by an Author. By visualizing these relationships statically, teams gain a shared understanding of how the review system is structured, which roles interact with which objects, and what state transitions are possible at each stage of the workflow.

## When to Use This Template

This template is most valuable when you are designing or documenting a code review tool, integrating a review workflow into a larger CI/CD pipeline, or onboarding engineers to an existing review system. If your team is building a custom PR platform, extending GitHub or GitLab APIs, or enforcing review policies programmatically, a class diagram helps clarify the data model before writing a single line of code. It is also useful during architecture reviews when stakeholders need to understand how review-related objects relate to broader concepts like branches, builds, and deployments without getting lost in sequence-level detail.

## Common Mistakes to Avoid

One frequent mistake is conflating a class diagram with a flowchart or sequence diagram. A class diagram shows structure — what objects exist and how they relate — not the step-by-step flow of events. Avoid adding swimlanes or arrows that imply time-ordered actions; use a sequence or activity diagram for that purpose instead. Another pitfall is over-modeling: including every possible attribute of a PullRequest (timestamps, labels, CI status, diff stats) can make the diagram unreadable. Focus on the attributes and relationships that are architecturally significant to the review process itself. Finally, neglect of multiplicity annotations (1..*, 0..1, etc.) is a common oversight that leaves ambiguity about whether a PR can have zero reviewers or whether a comment must always belong to a review thread. Precise multiplicity makes the diagram actionable rather than merely decorative.