Restful State Machines and SQL Database

State machines and a relational database may look like completely unrelated tools, yet they form an interesting couple. By supporting them with well-established architectural patterns and principles, we built a model layer of a web application which utilizes the formal aspects of the state machines to aid the development of the application while standing on traditional technologies. The layered approach fits well with existing frameworks and the Command-Query Separation pattern provides a horizontal separation and compatibility with various conceptually distinct storages, while the overall architecture respects RESTful principles and the features of the underlying SQL database. The integration of the explicitly specified state machines as first-class citizens provides a reliable connection between the well-separated formal model and the implementation; it enables us to use visual comprehensible formal models in a practical and effective way, and it opens new possibilities of using formal methods in application development and business process modeling.