st=>start: Start
s1=>subroutine: 客户选购商品
s2=>subroutine: 商户提交支付订单
s3=>subroutine: 第三方支付平台处理
s4=>subroutine: 向银行发起扣款请求
s5=>subroutine: 返扣款付结果
s6=>subroutine: 返回商户显示购买成功
s7=>subroutine: 转发支付请求
s8=>subroutine: 客户输入支付卡号、密码
cond=>condition: 直连支付?
ed=>end: End
st->s1->s2->cond(yes)->s3->s4->s5->s6->ed
cond(no)->s7->s8->s5