For an online article I am writing for my Goverment Computer News column (called reality check), I am releasing an alpha release of my Java software called the Easy Knowledge Base Editor (or EzKb for short). I created a Windows installer and Windows executable that you can download here. If there is interest I will create a manual install with the Jar files for Linux and MacOS installations.
There are some help files (but I need to create many more) and some youtube videos on my youtube channel to give you an introduction to the software and some of the things that it can do. Be warned that this is alpha software so it is not feature complete. It has integrated maps and an integrated wordnet dictionary.
The way to think about this software is that each tab represents a layer in your knowledge base, starting from the smallest layer (a single fact) to more complex layers like things (aka Entities or Classes), to a relationship editor (connect things to create relationships) to rules (if-then constructs) to triggers (when to execute rules) and many other items (like a .csv file import). I have a grand vision for this software and frankly, not enough time to actually create what I envision. So, I am releasing it in this alpha state and then will continue to improve it (as time permits).