Business Model - Card Game Results Tracking System

Business/Conceptual Model

Here is the business model presented using (expectedly) Entity-Relationship diagram.

No surprises in the business model.

Now, to the not-so-easy part, the business rules.

1. The only allowed values for Match Scores are even integers
2. Sum (Match Score) for each match (identified by Match ID) has to be zero
3. Count of players for each match (identified by Match ID) has to be either 3 or 4
4. If a Match Score exists, it has to contain scores for all players who played the match. These players have to be the same as the players in the Match Draw for the same match.
5. One player can only play one match in each round of any tournament
6. Match table has to exists for each match of a round or for none of them
7. Match Points are calculated as per the explanations in the business requirements (BRD).