abstract contract Vat {

    struct Urn {
        uint256 ink;   // Locked Collateral  [wad]
        uint256 art;   // Normalised Debt    [wad]
    }

    struct Ilk {
        uint256 Art;   // Total Normalised Debt     [wad]
        uint256 rate;  // Accumulated Rates         [ray]
        uint256 spot;  // Price with Safety Margin  [ray]
        uint256 line;  // Debt Ceiling              [rad]
        uint256 dust;  // Urn Debt Floor            [rad]
    }

    mapping (bytes32 => mapping (address => Urn )) public urns;
    mapping (bytes32 => Ilk)                       public ilks;
    mapping (bytes32 => mapping (address => uint)) public gem;  // [wad]

    function can(address, address) virtual public view returns (uint);
    function dai(address) virtual public view returns (uint);
    function frob(bytes32, address, address, address, int, int) virtual public;
    function hope(address) virtual public;
    function move(address, address, uint) virtual public;
    function fork(bytes32, address, address, int, int) virtual public;
}
function can(address, address) virtual public view returns (uint);
// [wad]