No, not electrocardiogram, Emacs Knowledge Graph. It’s a small project by Andrew Hyatt that is best thought of as light weight Zettelkasten sort of like the popular Emacs applications Org-roam and Denote.
Take a look at the GitHub README for an explanation of the project. There’s also a shorter description of the application on reddit but the best explanation is this video on ekg that demonstrates the app and discusses the design. The video is just short of 46 minutes so you’ll need to schedule some time.
One way of thinking about the project is that it’s Hyatt’s attempt to overcome the limitations imposed by Org’s “everything is text” principal. A practical consequence of this is that explicit forward and back links get replaced by tags. This makes linking notes essentially automatic: if two links share a tag, then they’re linked and discoverable from each other. To make this idea more useful, tags can be multiple words. Everything, even the note text, is stored in an sqlite database so searching is fast and effortless.
The project is still fairly new—although it is in Melpa—and Hyatt is still struggling with some of the concepts but he’s been using it at work for several months and hasn’t found any problems. All of this is explained in the video and if you have any interest at all in the package, you should spend the time to watch it.
This looks like an interesting project and it’s one I can see myself adopting. It seems like an excellent way to keep a set of notes: it’s easy to add notes and to find them later.