去中心化数据：Ocean Protocol数据市场

import hashlibimport jsonfrom dataclasses import dataclass, field  @dataclassclass DataToken:    """数据代币：代表数据集的访问权，而非数据本身"""    asset_id: str    owner: str    total_supply: int    price: float    holders: dict = field(default_factory=dict)     def mint(self, buyer: str, amount: int) -> bool:        """铸造代币并转移给购买者"""        if amount <= 0 or amount > self.total_supply:            return False        self.holders[buyer] = self.holders.get(buyer, 0) + amount        self.total_supply -= amount        return True     def to_dict(self):        return {            "asset_id": self.asset_id,            "owner": self.owner,            "total_supply": self.total_supply,            "price": self.price,            "holders": self.holders,        }  class ComputeToData:    """计算到数据：算法容器进入数据域，数据不出域只出结果"""     def __init__(self, secret_data: dict):        self.secret_data = secret_data        self.execution_log: list = []     def run_algorithm(self, algo: str) -> float:        """在数据域内执行算法，只返回计算结果"""        result = None        if algo == "sum":            result = sum(self.secret_data.values())        elif algo == "avg":            result = sum(self.secret_data.values()) / len(self.secret_data)        elif algo == "max":            result = max(self.secret_data.values())        self.execution_log.append({"algo": algo, "result": result})        return result  def verify_provenance(data: dict) -> str:    """对数据资产元数据做哈希指纹，确保链上记录不可篡改"""    raw = json.dumps(data, sort_keys=True).encode("utf-8")    return hashlib.sha256(raw).hexdigest()  if __name__ == "__main__":    patient_data = {"a": 12, "b": 18, "c": 15, "d": 22, "e": 20}    hospital_node = ComputeToData(patient_data)     avg_age = hospital_node.run_algorithm("avg")    max_age = hospital_node.run_algorithm("max")     print("计算结果(数据未离开医院节点): avg_age =", avg_age)    print("计算结果(数据未离开医院节点): max_age =", max_age)    print("执行日志:", hospital_node.execution_log)     token = DataToken(asset_id="hospital-001",                      owner="hosp01", total_supply=1000, price=0.05)    ok = token.mint(buyer="ai-company", amount=200)    print("代币交易成功:", ok)    print("访问权余额:", token.holders["ai-company"])    print("数据资产指纹:", verify_provenance(token.to_dict()))