Deep Diffs: visually exploring the history of a document

Software tools are used to compare multiple versions of a textual document to help a reader understand the evolution of that document over time. These tools generally support the comparison of only two versions of a document, requiring multiple comparisons to be made to derive a full history of the document across multiple versions. We present Deep Diffs, a novel visualisation technique that exposes the multiple layers of history of a document at once, directly in the text, highlighting areas that have changed over multiple successive versions, and drawing attention to passages that are new, potentially unpolished or contentious. These composite views facilitate the writing and editing process by assisting memory and encouraging the analysis of collaboratively-authored documents. We describe how this technique effectively supports common text editing tasks and heightens participants' understanding of the process in collaborative editing scenarios like wiki editing and paper writing.