History Flow (HF), developed by IBM, is a tool for visualizing dynamic, evolving documents and the interactions of multiple collaborating authors. As IBM explains, consider a scenario where three people will make contributions to a Wiki page at different points in time. Each person edits the page and then saves their changes to what becomes the latest version of that page.
The vertical red line represents the first version of the document. Since Mary creates the page all of the contents in the page reflect her author color. The length of the line indicates the amount of text Mary has written.
Suzanne adds some text to the end of Mary’s original entry; note that Suzanne’s blue line is appended to the end of Mary’s red line indicating that Suzanne’s text was added at the end of the page. Suzanne saves her changes and this becomes the latest version of the page.
History flow connects text that has been kept the same between consecutive versions; in other words, it connects corresponding segments on the lines representing versions. Pieces of text that do not have correspondence in the next (or previous) version are not connected and the user sees a resulting “gap” in the visualization; this happens for deletions and insertions.
Examples: Chocolate – The picture below shows the history of the Wikipedia article on chocolate. What jumps out? The zigzag pattern at the right. It turns out that this is an argument over whether a certain type of surrealist sculpture exists or not.
Example: Abortion – The image below is the diagram for the article on abortion. The black gashes show points where the article has been deleted and replaced with offensive comments. This type of vandalism turns out to be common on controversial articles.