This looks nicely done. Entities with only a single attribute are unnecessary but I suspect that there may be other relevant attributes contained within them when you look closely at how the data are actually used. For example, in the CategoryType I suspect that people might IRL refer to things like MMORPG or Sim as an abbreviation that might be expanded as a full name for reporting. It is also possible you might find subtypes, that might be relevant in a system like this. Of course, in the physical database you might well use these as lookup tables with surrogate keys - now that it is normalized it is quite fine and often a good idea to use them.

Hi Louis, 

Your ERD looks really good! I spent a bit of time looking at the details, and have one observation: the relationship from the publisher to the expansion entities is modeled as one-to-many (or mandatory, many). I think this implies that each publisher MUST have an expansion to their name. It depends on the business scenario of course, but if I'm understanding this correctly, I'd think a publisher could publish a game but not have any expansions under their belt. 

Anyway, just thought I'd mention that small point. All in all, looks pretty solid to me!

Thank you for the feedback.

@Eric, correct that should have been 0-to-many.