A member of a team of game developers, you have been tasked with devising a way to track players’ possessions. Possessions may be purchased from a catalog, traded with other players, or awarded for game activities. Possessions are categorized as clothing, tools, books, and coins. Players may have any number of possessions of any type. Players can search for other players who have particular possession types to facilitate trading. The game designer has informed you that there will likely be new types of possessions and ways to acquire them in the future. What kind of a data store would you recommend using?