Principal: a principal can represent anything from users, clients and servers to cells.
主体：主体可以表示从用户、客户端和服务器到单元的任何实体。
2
Foreign group UUIDs: the UUIDs of the groups registered in remote cells to which this principal belongs.
外来组uuid：此主体所属的、在远程调用中注册的组的UUID。
3
The invasion and spread of cancer cells to other parts of the body, known as metastasis, is a principal cause of death in patients diagnosed with breast cancer.