Communicating Formal Proofs: The Case of Flyspeck

We introduce a platform for presenting and cross-linking formal and informal proof developments together. The platform supports writing natural language ‘narratives’ that include islands of formal text. The formal text contains hyperlinks and gives on-demand state information for each proof step. We argue that such a system significantly lowers the threshold for understanding formal development and facilitates collaboration on informal and formal parts of large developments. As an example, we show the Flyspeck formal development (in HOL Light) and the Flyspeck informal mathematical text as a narrative linked to the formal development. To make this possible, we use the Agora system, a MathWiki platform developed at Nijmegen which has so far mainly been used with the Coq theorem prover: we show that the system itself is generic and easily adapted to the HOL Light case.