Personal library project ER-diagram

digraph ERDiagram {
    // This is the ER-diagram for a personal library management app project. It'll end up on github one day!

    rankdir=BT;

    // The different entities in our data set.
    books [shape=box, color=blue];
    user [shape=box, color=red];
    acquaintance [shape=box, color=red];

    // The different attributes in our data set.
    metadata [shape=oval, color=blue];
    "config data" [shape=oval, color=red];

    // The different relationships we have;
    owns [shape=diamond, color=blue];
    wants [shape=diamond, color=blue];
    lends [shape=diamond, color=red];
    borrows [shape=diamond, color=red];
    "exchanges\nwith" [shape=diamond, color=red];

    // The main component in our case is, ofc, books. So here they are!
        metadata -> books;

        // Things can happen to books.
        owns -> books ;
        wants -> books;
        lends -> books;
        borrows -> books;

    // We also have user of our app. He's the chief librarian in a sense.
        // He has a password, a username, etc...
        "config data" -> user;
        // He interacts with his books...
        user -> owns; // Our user owns books.
        user -> wants; // Or sometimes wants them in a wishlist.

        // ...and with other people.
        user -> "exchanges\nwith"; // He also knows other people that read books.
        user -> lends;

    // And so we have the aforementioned other people.
        // They also interact with books, but we don't care about their books, only ours.
        acquaintance -> borrows;

        // But they mostly interact with user.
        acquaintance -> "exchanges\nwith";

    {rank=max; metadata}
}