It has been a while since I introduced state-based State Tree Structure (STS) framework for the Supervisory Control Theory (SCT). You might have some basic knowledge about SCT, or you might have already known a lot about the STS framework. I made bold claim that this framework was great at attacking large DES systems. I mean it! To back up my statement, I decide to make this library open source. So researchers can have the free(dom) to use this library for whatever purpose they want. The beauty of STS framework is, even though the underlying details seem complex, the resulting synthesis can be summarized by a couple of clean and short formulas. If you happened to have read my Ph.D. thesis, or the book, "Nonblocking Supervisory Control of State Tree Structures", you may notice that I used the same symbols in my C++ classes to implement the concepts in my thesis. It just works! There are certain parts I'd like to improve. For example, the current lib only supports STS and specifications in an ad-hoc format. An XML format will be a much better choice. I also like to see a BDD-to-IDD (Integer Decision Diagram) conversion class to make the resulting control functions easier to be understood. At last, the core bdd synthesis procedure can be improved. Go to STSLib directory to find out how to install the library in your computer.