I have been following the development of a new database called TypeDB (formerly Grakn) for some time. As the name suggests, this is a database with an emphasis on a strong type-system. At first this might not sound revolutionary; most relational databases have type systems. What makes TypeDB unique is that it allows for user-defined types and the ability to attach logic to these types. Combined with this, the database offers an inference engine that can allow the database to deduce facts about your data. Subjectively this feels somewhat like writing a Prolog program. I'm excited to see where this database goes.
For those who are interested, you can find out more about TypeDB here.