pragma solidity ^0.4.9;

contract MultiPartyContract {

    // a multi-party document `authenticity` scheme where by
    // the 3 hard-coded owners are certifying the authenticity of a single document

    address constant owner1 = 0x0;
    address constant owner2 = 0x0;
    address constant owner3 = 0x0;

    bytes32 constant public document = 0x0;

    mapping (address => bool) attestations;

    function setAttestation(bool valid){
        attestations[msg.sender] = valid;
    }

    function isValid() constant returns (bool) {
        if (attestations[owner1] && attestations[owner2] && attestations[owner3])
            return true;
         else
            return false;
    }

}