Mumbai, India, is described in the title of a recent book as the "Maximum City." With over 14 million people, Mumbai is one of the largest and most densely populated urban areas on the planet. Over the past few years, architects, urban planners, and activists from the Collective Research Initiatives Trust (CRIT) in Mumbai have painstakingly assembled rich geographic data sets detailing information about the city down to the building level. This data has been used to devise and promote alternative development plans for housing some of the city's seven million squatters and slumdwellers. Now that the data exists and is publically available, how can CRIT ensure that it continues to be maintained and developed into the future?

Yochai Benkler has written at length about open source software development and its extension into what he calls generalized "commons-based peer-production," to distinguish collaborative projects like Wikipedia and the Linux kernel from traditional modes of strictly commerce-driven economic practice. The history of commons-based peer-production on the Internet has yielded some insight into the types of organizing structures these projects use to grow and evolve in the absence of the traditional carrot-and-stick arrangements of business and academia. Tim O'Reilly loosely terms these structures "the architecture of participation," but is the definite article he uses somewhat misleading? In looking at existing common-based production modes, we see not merely a single architecture of participation, but many different ones, composed of related practices.

As if it weren't enough to simply pose the technical challenges of mapping a city of millions with no budget to speak of, the Mumbai Free Map project also uncovers interesting questions on the collaborative development of structured data sets. How can we maximize the benefits of distributed collaboration, while mitigating the risk to quality and accuracy? How can a community composed of disparate interests not only aggregate data usefully, but also evolve information designs that best embody the data it seeks to collect? By considering the possible architectures of participation reflected in projects like Apache, Wikipedia, Advogato, and OpenStreetMap, we can begin to envision a set of "design patterns" -- a term taken from the field of architecture itself -- for implementing commons-based peer-production. As more and different efforts like OpenStreetMap and the Mumbai Free Map undertake to explore these design patterns, the origin, role, and conception of "geographic data" (as we think of it now) seems likely to undergo a radical shift.