Aggregate Root Choice (for all Football/Soccer fans)

Question

I have been reading StackOverflow for weeks, but I still could not decide whether my DDD Aggregate Root choice is correct. Long story short -- here are the entities. It is about the football/soccer domain:

League, Team and Match

Each Team can participate in one or more Leagues by playing Matches (i.e. English Premier League, UEFA Champions League). Each team has HomeMatches and AwayMatches in a certain League. Each Match has a League, HomeTeam and AwayTeam.

Each League has many Matches.

I think I need to have two repositories -- LeagueRepository where I can get all the matches for a certain league for a certain period. Through this repository I will automatically update the database when a round of matches has been played and I will record the results accordingly.

I also need a TeamRepository, where I can get all the Matches for a certain team in different leagues for different periods of time. This is for statistical purposes, i.e. give me all Liverpool Home Matches in the English Premier League for the last 10 years. Yeah, you guessed right -- it is about betting chances and odds calculations :)

Long story short -- my Domain is the Football/Soccer World. Those of you who follow the sport know those details and what a League, Team and Match is.

Is it OK to have two separate aggregate roots -- League and Team. I can reach a given match through either one of them. Is this OK with the DDD design?

Or should I introduce a new Entity called Sport and make it the sole aggregate root. Then a Sport will have many Leagues and many Teams.

I am using EF code-first approach and I am trying to identify my Repositories and aggregate roots. If you were designing this database, how would you structure those three entities -- League, Team and Match. Of course we are over-simplifying things here.

All your thoughts and comments will be greatly appreciated.

Thanks in advance.

Answer 1

To me, Sport seems like a waste of a concept. If you don't need to model, soccer, baseball, basketball, etc then I imagine the sport model would be mostly empty and a waste of space. If you think of your program in terms of teams and leauges, then that is the two repositories I would stick with. What advantage to a Sport repository do you see other then just having one root?

Answer 2

Three white papers that you should read to better understand how you should go about choosing your aggregates: http://dddcommunity.org/library/vernon_2011/