If I had six months to research something, I'd work on temporal databases, starting with the book Developing Time-Oriented Database Applications in SQL. I'd loo

If I had six months to research something, I'd work on temporal databases, starting with the book Developing Time-Oriented Database Applications in SQL. I'd look at the history of attempts to bring this into the SQL standard, including the arguments between Snodgrass and Date, and what was eventually put in SQL2011. Then I'd see how much of this Postgres supports, and possibly take a shot and filling in some gaps. Or I'd try to adapt a popular ORM to work with temporal tables. But that is me. Pick something that interests you! By the way, for six months, you had better pick something very focused. I would try to err on the side of modest. If all you have right now is a broad topic, see if you can pull at one loose thread---some annoyance or nagging question---and see where it takes you. Probably you will find hundreds of articles to read, and more complexity than you expected. Grad school is a rare chance to "go down the rabbit hole", but you should expect that your six months will fly by. Research is like reading Wikipedia: it constantly branches and takes you into new things you "need" to know.