Use Case Diagram for the Chess Game

In this lesson, we’ll build the use case diagram for the online chess game system and understand the relationship between its main actor and core functions. First, let’s define the different elements of our chess game, followed by the complete use case diagram of the system.

System

Our system, the Online Chess game, manages a standard chess match between two players over an online platform, strictly following official chess rules.

Actors

Here are the main actors of our chess game.

Primary actors

• Player: The primary and only actor in this system. A player participates in the chess game by making moves, viewing the game state, and may end the game by resigning or forfeiting.

Use cases

In this section, we’ll define the use cases for the chess game. We have listed the use cases according to their interactions with a particular actor.

Player

• Start new game: Initiate a new chess match as either white or black.

• Make move: Select and move a chess piece according to the official rules, including special moves (castling, en passant, pawn promotion).

• View game state: View the current board position, move history, and game status at any point during the match.

• Resign/Forfeit game: Voluntarily end the game before its conclusion, conceding victory to the opponent.

System

• Validate move: Whenever a player attempts to make a move, the system validates that the move is legal according to all chess rules, including detection of check, checkmate, castling, en passant, and pawn promotion.

• Declare results: After every move, the system checks for endgame conditions such as checkmate, stalemate, draw (by threefold repetition, 50-move rule, or insufficient material), resignation, or forfeiture, and declares the appropriate result.

Relationships

This section describes the relationships between and among actors and their use cases.

Include

• “Make move” includes “Validate move:”

  • Every time a player moves, the system must validate that move according to chess rules (including check, checkmate, stalemate, en passant, castling, and promotion).

• “Validate move” includes “Declare results:”

  • After each move is validated, the system checks if the game has reached an end condition (checkmate, stalemate, draw, etc.) and declares the result if appropriate.

• “Resign/Forfeit game” includes “Declare results:”

  • When a player resigns or forfeits, the game ends immediately, and the system must declare the result (the opponent wins by resignation or forfeiture).

Associations

The table below shows the association relationship between actors and their use cases.