Deriving Valuable Requirements through Business Modeling and Use‑Case Analysis

In "Google Software Engineering" a quote says that code is a liability, not an asset; the real value lies in the product problems the code solves. The article stresses that writing code for a wrong requirement wastes effort, so the first step is to model the business and clarify the true needs.

Business modeling starts with locating the "battlefield" – the target organization and its "boss" – and then defining a clear vision expressed as a measurable improvement goal (e.g., reducing average cafeteria payment time from five minutes to three minutes).

An illustrative case studies a school cafeteria where long queues are caused by students searching for cards. By analyzing the organization, the target organization (a specific elementary school cafeteria) and the decision‑maker (the logistics manager) are identified, and a vision to improve payment efficiency is set.

The next phase derives concrete use‑cases from the business model, distinguishes business from system use‑cases, and writes a detailed requirement specification. The specification includes pre‑conditions, post‑conditions, stakeholder interests, basic and alternative flows, field lists, business rules, quality requirements and design constraints.

前置条件：
       存在已经完成签约的学生账户
后置条件：
       扣款凭证已经关联一笔扣款成功的支付订单
涉众利益：
       家长--担心由于忘记充值，账户内余额不足而导致孩子无法吃饭
       餐厅老板--担心卖出饭但是没有收到对应的款项
       系统提供商老板--担心出现大量垫资未还的欠款，产生坏账造成资金损失
基本路径：
       1. 服务商收银系统提交消费信息
       2. 系统提示学生刷脸
       3. 系统验证刷脸学生账号签约状态
       4. 系统请求 XX 支付扣款
       5. 系统保存扣款结果
       6. 系统返回扣款单信息
扩展路径：
       3a. 学生账号未签约：
             3a1. 系统通知家长签约
       4a. 扣款账户余额不足：
             4a1. 系统校验垫资条件
                     4a1a. 不满足垫资条件
                     4a1a1. 转到5
             4a2. 系统请求 XX 支付扣款
             4a3. 系统通知家长还款
字段列表：
       1. 消费信息=消费金额+商户订单号
       2. 扣款单信息=扣款金额+是否垫资+支付订单号
业务规则：
       1. 单学生账户最多同时存在3笔欠款
       2. 垫资只针对消费金额小于30元的订单
       3. 每个学校有垫资上限，垫资上限=学生数*3*30*10%
质量需求：
       1. 扣款从收到请求到结束在5秒内完成
设计约束：
       1. 收款系统使用 XX 支付

By following this structured approach, teams can ensure that every requirement is justified, measurable, and aligned with the organization’s true goals, paving the way for efficient implementation and later phases of analysis and design.