OBJECT IDENTIFIERS

• Each Continent and Ocean is assigned a unique 2 digit ID number.

  class Continent object
  {
     Continent_ID : integer (0..99)
  }

• Each city is assigned a compound two-part identifier. The first part simply duplicates the city's continent ID (this is redundant; cities are considered immobile. Or are they?). The second part is a two digit number assigned at generation time, and unique among cities on that continent.

  class City object
  {
     Continent_loc : Continent ;
     City_ID : integer(0..99)
  }

• Each piece is assigned a compound multi-part identifier. The first two parts identify the continent and city of manufacture; the next part describes the piece type; and the final part is a number assigned sequentially upon production. Collectively, these parts are known as the piece's "license plate".

  class Piece_ID : object
  {
     Location_of_Manufacture : City ;
     Piece_Type : integer(0..99) ;
     Production_Number : integer(0..9999)
  }