%% 用例图：12306旅客管理系统
graph LR
    %% 参与者
    actor "普通用户" as User
    actor "管理员" as Admin
    actor "支付平台" as Payment

    %% 用例
    uc1["注册账号"]
    uc2["登录系统"]
    uc3["管理旅客"]
    uc4["查询车次"]
    uc5["购买车票"]
    uc6["支付订单"]
    uc7["查看订单"]
    uc8["退票"]
    uc9["改签"]
    uc10["候补购票"]
    uc11["设置默认旅客"]
    uc12["查看乘车记录"]
    uc13["管理用户"]
    uc14["系统配置"]

    %% 关系
    User --> uc1
    User --> uc2
    User --> uc3
    User --> uc4
    User --> uc5
    User --> uc6
    User --> uc7
    User --> uc8
    User --> uc9
    User --> uc10
    User --> uc11
    User --> uc12

    Admin --> uc13
    Admin --> uc14

    Payment --> uc6

    %% 包含关系
    uc5 --> uc6 : <<include>>

    %% 扩展关系
    uc10 -.-> uc5 : <<extend>>
