"They Can Only Ever Guide": How an Open Source Software Community Uses Roadmaps to Coordinate Effort

Unlike in commercial software development, open source software (OSS) projects do not generally have managers with direct control over how developers spend their time, yet for projects with large, diverse sets of contributors, the need exists to focus and steer development in a particular direction in a coordinated way. This is especially important for "infrastructure" projects, such as critical libraries and programming languages that many other people depend on. Some projects have taken the approach of borrowing planning tools that originated in commercial development, despite the fact that these techniques were designed for very different contexts, e.g. strong top-down control and profit motives. Little research has been done to understand how these practices are adapted to a new context. In this paper, we examine the Rust project's use of roadmaps: how has an important OSS infrastructure project adapted an inherently top-down tool to the freewheeling world of OSS? We find that because Rust's roadmaps are built in part by summarizing what motivated developers most prefer to work on, they are in some ways more a description of the motivated labor available than they are a directive that the community move in a particular direction. They allow the community to avoid wasting time on unpopular proposals by revealing that there will be little help in building them, and encouraging work on popular features by making visible the amount of consensus in those features. Roadmaps generate a collective focus without limiting the full scope of what developers work on: roadmap issues consume proportionally more effort than other issues, but constitute a minority of the work done (i.e issues and pull requests made) by both central and peripheral participants. They also create transparency among and beyond the community into what central contributors' plans are, and allow more rational decision-making by providing a way for evidence about community needs to be linked to decision-making.