to start a discussion : I see 4 kinds of tournaments.
1. Championship : each participant plays one opponent, winner goes on to next round.
2. Closed tournament : fixed number of players, each playing all the others (single or double)
3. Open tournament : open for anyone who wants to take part, but limited number of games (ex. in 'weekend' tournaments normally 7 games). FIDE Swiss rules for pairing, but needs all games of a round to be finished before next pairing can be calculated.
4. USA-ROW style.
If I would have to code one of these, I'd prefer the closed tournament.