📚 Year 12 WJEC Computer Science: Case Study Practical Exercises | WJEC计算机 Year 12: 案例分析实战演练
Case studies form the backbone of the WJEC Year 12 Computer Science course, bridging the gap between abstract theory and tangible application. They require you to dissect complex scenarios, propose system solutions, design algorithms, and reflect critically on your choices. Mastering this skill not only boosts exam performance but prepares you for real-world software development and IT consultancy. This article provides a structured guide to tackling case study practical exercises, complete with worked examples and revision tips.
案例分析是WJEC Year 12计算机科学课程的核心，它架起了抽象理论与实际应用之间的桥梁。你需要剖析复杂情境，提出系统解决方案，设计算法，并对自己的选择进行批判性反思。掌握这项技能不仅能提升考试成绩，还能为未来的软件开发与IT咨询工作做好准备。本文提供攻克案例分析实战练习的结构化指南，并配有完整示例和复习建议。
1. The Role of Case Studies in WJEC Computer Science | 案例研究在WJEC计算机科学中的角色
WJEC case studies are designed to simulate the challenges faced by computing professionals. They test your ability to interpret user needs, model data, devise efficient algorithms, and justify technical decisions. Examiners look for logical thinking, clear documentation, and awareness of legal and ethical implications. By repeatedly engaging with practice scenarios, you train yourself to spot core requirements and avoid irrelevant detail.
WJEC的案例研究旨在模拟计算专业人员面临的挑战。它们考查你解读用户需求、数据建模、设计高效算法以及论证技术决策的能力。考官看重逻辑思维、清晰的文档以及对法律与伦理影响的认识。通过反复练习情境题目，你能练就识别核心需求、避开无关细节的本领。
2. Analysing the Problem Scenario | 分析问题情境
Begin by reading the scenario statement at least twice. Underline keywords such as 'real-time', 'secure', 'multi-user', or 'mobile'—these signal non-functional and quality requirements. Summarise the current system's limitations in one sentence. Then, rephrase the problem in your own words to confirm understanding. A precise problem statement prevents scope creep and sets the foundation for a focused solution.
首先至少阅读情境描述两遍。划出关键词，如“实时”、“安全”、“多用户”或“移动端”——这些提示了非功能性需求和质量要求。用一句话概括现行系统的局限。接着用自己的话复述问题，以确保理解准确。精确的问题陈述能防止范围蔓延，并为有针对性的解决方案奠定基础。
Create a simple context diagram to visualise external entities (users, other systems) and data flows. This high-level snapshot helps you confirm boundaries. For example, a library case study might show Members, Librarian, and Book Supplier as external entities interacting with the central Library System. Keep the diagram clear and label all flows.
绘制简单的上下文图来可视化外部实体（用户、其他系统）和数据流。这个高层快照有助于确认系统边界。例如，图书馆案例研究可能显示会员、图书管理员和图书供应商作为外部实体与中央图书馆系统交互。保持图表清晰，并标注所有数据流。
3. Stakeholder Identification and Requirements Gathering | 利益相关者识别与需求收集
List all stakeholders: direct users, indirect beneficiaries, managers, and third parties. For each, note their main goal and how the system must serve them. Use a table to organise this information efficiently; it demonstrates structured analysis. Remember that stakeholders often have conflicting needs, and a good solution explains trade-offs.
列出所有利益相关者：直接用户、间接受益者、管理者以及第三方。为每一方注明其主要目标以及系统必须如何满足他们。使用表格高效组织这些信息，这能体现你有条理的分析。注意利益相关者之间常有冲突需求，好的方案应解释权衡取舍。
| Stakeholder 利益相关者 | Goal 目标 | System Requirement 系统需求 |
|---|---|---|
| Library Members | Quick book search and reservation | Online catalogue with real-time availability |
| Librarian | Efficient issue/return processing | Barcode scanner integration, fine calculation |
Requirements are often split into functional and non-functional. Functional requirements describe what the system does (e.g., 'generate overdue notices'), while non-functional ones describe how it performs (e.g., 'respond within 2 seconds'). During the exam, always mention both types to show depth of analysis.
需求通常分为功能性和非功能性两类。功能性需求描述系统做什么（如“生成逾期通知”），而非功能性需求描述系统如何运作（如“2秒内响应”）。考试时务必提及两类需求，以显示分析的深度。
4. Feasibility Study and Project Constraints | 可行性研究与项目限制
Even in a paper-based exercise, you should touch upon feasibility: technical (can we build it with available technology?), economic (are costs justified?), legal (GDPR compliance), and operational (will staff adopt it?). Mentioning constraints such as budget, time, and legacy hardware demonstrates real-world awareness. Link constraints back to requirements; for instance, limited budget may rule out biometric authentication.
即使在纸笔练习中，你也应该提及可行性：技术可行性（能否用现有技术构建？）、经济可行性（成本是否合理？）、法律可行性（是否符合GDPR？）以及运营可行性（员工会采用吗？）。提及预算、时间和旧硬件等限制，能展现对现实世界的认知。将限制与需求联系起来；例如，预算有限可能排除生物识别认证。
Also discuss ethical considerations. A case study involving personal data must address how consent is obtained and data is protected. WJEC values candidates who can spot potential dilemmas early and propose mitigation, such as anonymisation or role-based access control.
同时讨论伦理考量。涉及个人数据的案例研究必须说明如何获取同意以及如何保护数据。WJEC欣赏能及早发现潜在困境并提出缓解措施的考生，比如数据匿名化或基于角色的访问控制。
5. Designing Algorithms: Flowcharts and Pseudocode | 设计算法：流程图与伪代码
Once requirements are clear, model the logic with flowcharts and pseudocode. Flowcharts are excellent for communicating decision structures to non-technical stakeholders; pseudocode is closer to implementation. Keep pseudocode language-agnostic and consistent—use keywords like IF, ELSE, WHILE, FOR, and PROCEDURE. WJEC expects clear indentation and meaningful variable names.
一旦需求明确，就使用流程图和伪代码来建模逻辑。流程图非常适合向非技术利益相关者传达决策结构；伪代码则更接近实现。保持伪代码与语言无关且风格一致——使用IF、ELSE、WHILE、FOR和PROCEDURE等关键词。WJEC期望清晰的缩进和有意义的变量名。
Here is an example of a linear search algorithm in pseudocode for a library catalogue lookup. Notice the use of a loop and a sentinel value to indicate 'not found'.
以下是一个用于图书馆目录查询的线性搜索算法伪代码示例。注意使用了循环和表示“未找到”的标记值。
PROCEDURE searchCatalogue(isbn, catalogue)
FOR i ← 0 TO LENGTH(catalogue) – 1
IF catalogue[i].isbn = isbn THEN
RETURN catalogue[i].title
END FOR
RETURN 'Not Found'
END PROCEDURE
Always trace your algorithm with sample data to verify correctness. Mention time complexity informally if it strengthens your answer—e.g., 'linear search runs in O(n) time, which is acceptable for small collections but would be slow for a million books'. Use the Unicode superscript for squared if needed, e.g., O(n²).
始终使用样本数据追踪算法以验证正确性。若有助于答案，可非正式地提及时间复杂度——例如，“线性搜索以O(n)时间运行，对于小型馆藏可接受，但对于百万图书会很慢”。需要时使用Unicode上标，如O(n²)。
6. Data Structures and Database Design | 数据结构与数据库设计
Identify the key entities from the scenario and draw an entity-relationship diagram (ERD). For a library system, entities might be Member, Book, Loan, and Reservation. Define attributes and primary keys—use underlining to denote PK in text-based answers. Explain relationships: one member can have many loans (1:M), and a loan links one member to one book.
从情境中识别关键实体，并绘制实体关系图（ERD）。对于图书馆系统，实体可能包括会员、图书、借阅和预约。定义属性与主键——在文本答案中可用下划线表示主键。解释关系：一个会员可以有多笔借阅（1:M），一笔借阅联系一个会员和一本书。
Normalise your data to at least Third Normal Form (3NF) to avoid redundancy. Show the steps: 1NF removes repeating groups, 2NF removes partial dependencies, and 3NF removes transitive dependencies. WJEC exam questions often ask you to identify normalisation errors in a given table; practicing these conversions builds confidence.
将数据至少规范化到第三范式（3NF）以避免冗余。展示步骤：1NF消除重复组，2NF消除部分依赖，3NF消除传递依赖。WJEC试题经常要求你找出给定表格中的规范化错误；练习这些转换能增强信心。
7. User Interface Planning and Prototyping | 用户界面规划与原型设计
A well-designed interface improves user experience and reduces errors. Sketch a low-fidelity wireframe for key screens such as login, search results, and book detail. Annotate the wireframe to explain design choices: button placement, colour contrast, and navigation flow. Even short notes show the examiner you have considered human-computer interaction principles.
精心设计的界面能改善用户体验并减少错误。为关键页面（如登录、搜索结果和图书详情）绘制低保真线框图。为线框图添加注释，解释设计选择：按钮位置、色彩对比度和导航流程。简短的笔记就能向考官展示你考虑了人机交互原则。
Prototyping can be done on paper; describe how you would gather feedback from a sample of users. When refining the prototype, explain how you would incorporate accessibility features, such as screen-reader compatibility and keyboard navigation, to meet equality legislation.
原型制作可在纸上完成；描述你将如何从用户样本中收集反馈。在改进原型时，解释如何加入无障碍功能，如屏幕阅读器兼容性和键盘导航，以符合平等法规。
8. Implementation Strategy and Modular Coding | 实施策略与模块化编码
Break the solution into modules (e.g., user authentication, catalogue search, transaction processing). Explain the benefits: reusable code, easier testing, and parallel development. Use a structure chart to show module hierarchy and data passing. Mention a suitable programming paradigm—procedural for straightforward logic, object-oriented if the scenario has distinct entities with states.
将解决方案分解为模块（例如，用户认证、目录搜索、事务处理）。解释好处：代码可复用、更易测试、支持并行开发。使用结构图展示模块层次与数据传递。提及合适的编程范式——逻辑简单时用过程式，若情境中的实体具有明显状态则用面向对象。
For each module, outline the key variables and data structures. For instance, a Loan module might use an array of records or a linked list, depending on the need for fast insertion. Emphasise that your choices are justified by earlier analysis, not arbitrary.
为每个模块概述关键变量和数据结构。例如，借阅模块可能根据快速插入的需求使用记录数组或链表。强调你的选择是基于先前分析而论证的，并非随意决定。
9. Testing and Debugging Techniques | 测试与调试技术
Testing must be planned early. Distinguish between validation (checking data is sensible) and verification (ensuring the system meets specifications). Construct a test plan table that includes test ID, input data, expected outcome, actual outcome, and corrective action. Cover normal, boundary, and erroneous data.
测试必须尽早规划。区分验证（检查数据是否合理）和确认（确保系统符合规格）。构建测试计划表，包含测试编号、输入数据、预期结果、实际结果和纠正措施。覆盖正常、边界和错误数据。
| Test ID | Input | Expected | Type |
|---|---|---|---|
| T01 | Valid ISBN, book available | Loan recorded | Normal |
| T02 | Member has unpaid fines | Loan denied, message shown | Error |
Debugging techniques—such as dry-running, using trace tables, and inserting output statements—help isolate logic errors. A trace table is especially powerful: it tracks variable values step by step and often reveals off-by-one mistakes or incorrect loop conditions. WJEC expects you to demonstrate how you would use these tools during development.
调试技术——如干运行、使用跟踪表和插入输出语句——有助于隔离逻辑错误。跟踪表尤为强大：它逐行追踪变量值，常能揭示差一错误或不正确的循环条件。WJEC期望你展示在开发中如何使用这些工具。
10. Evaluation and Reflection | 评估与反思
Evaluation is a critical, often underused section. Compare your final solution against the original requirements. If certain features were not implemented due to constraints, explain why and suggest future enhancements. Reflect on the development process: what went well, what was challenging, and how you would approach the project differently next time.
评估是一个关键但常被忽略的环节。将你的最终解决方案与原始需求进行比较。若某些功能因限制未能实现，解释原因并提出未来改进建议。反思开发过程：哪些顺利、哪些具有挑战性，以及下次你会如何以不同方式处理该项目。
Use objective metrics, if possible—'search response time was within the 2-second target' carries more weight than 'the system was fast'. Refer back to your test results and stakeholder feedback. A mature evaluation that acknowledges weaknesses and proposes concrete improvements will impress examiners.
尽可能使用客观指标——“搜索响应时间在2秒目标以内”比“系统很快”更具说服力。回顾你的测试结果和利益相关者反馈。一份承认弱点并提出具体改进措施的成熟评估会给考官留下深刻印象。
11. Practical Walkthrough: School Library System | 实战演练：学校图书馆系统
Scenario: A school library currently uses a paper-based log. The librarian wants a digital system to manage book loans, reservations, and fines. Students should be able to search the catalogue online and renew books remotely. The budget is limited, and the system must comply with data protection rules.
情境：某学校图书馆目前使用纸质日志。管理员希望有一个数字系统来管理图书借阅、预约和罚款。学生应能在线查询目录并远程续借。预算有限，系统必须符合数据保护规定。
Step 1 – Problem statement: 'Develop a cost-effective, secure library management system that allows students to search, reserve, and renew books, while enabling staff to process loans and returns efficiently.' Requirements table:
步骤1 – 问题陈述：“开发一个成本效益高、安全的图书馆管理系统，使学生能够搜索、预约和续借图书，同时让工作人员高效处理借阅与归还。”需求表：
| Functional Requirement | Non-functional Requirement |
|---|---|
| Search catalogue by title, author, ISBN | Response time less than 2 seconds |
| Issue and return books with barcode scanner | 99.9% availability during school hours |
| Calculate fines automatically | GDPR-compliant data storage |
Step 2 – Algorithm for overdue fine calculation (pseudocode):
步骤2 – 逾期罚款计算算法（伪代码）：
PROCEDURE calculateFine(dueDate, returnDate, dailyRate)
IF returnDate > dueDate THEN
daysOverdue ← (returnDate – dueDate)
fine ← daysOverdue × dailyRate
RETURN fine
ELSE
RETURN 0
END PROCEDURE
Step 3 – Database design: three tables Member (memberID PK, name, form), Book (bookID PK, title, author, ISBN), Loan (loanID PK, memberID FK, bookID FK, dateOut, dateDue, dateReturned). Normalise to 3NF; show that Loan table removes repeating groups and has no transitive dependencies.
步骤3 – 数据库设计：三个表 Member（memberID PK, name, form），Book（bookID PK, title, author, ISBN），Loan（loanID PK, memberID FK, bookID FK, dateOut, dateDue, dateReturned）。规范化为3NF；说明Loan表消除了重复组且无传递依赖。
Step 4 – e day → fine 0, one day late → fine charged). Discuss trace tables for the fine algorithm.
步骤4 – 测试计划：包括使用边界日期测试逾期罚款（正好到期日归还→罚款为0，晚一天→收费）。讨论罚款算法的跟踪表。
This walkthrough models the depth expected in a WJEC case study response. Adapt the structure to any domain by consistently applying the analyse–design–implement–test–evaluate cycle.
本演练示范了WJEC案例分析回答中期望的深度。无论何种领域，只要持续运用分析—设计—实施—测试—评估循环，均可套用此结构。
12. Common Mistakes and Tips for Success | 常见错误与成功秘诀
One frequent error is jumping into design without clarifying requirements. Always restate the problem and list stakeholders first. Another pitfall is ignoring non-functional requirements; quality attributes like security and usability are often worth marks. Avoid overly complex algorithms when a simple, correct one suffices—explain your rationale.
常见错误之一是未澄清需求就急于设计。务必先复述问题并列出利益相关者。另一陷阱是忽略非功能性需求；安全、可用性等质量属性往往占分。当简单的正确算法就足够时，避免使用过度复杂的算法——解释你的理由。
Time management matters: allocate reading, planning, writing, and review phases. In the exam, bullet points and annotated diagrams can convey information faster than long paragraphs. Practice past WJEC case studies under timed conditions to build speed and confidence. Finally, link every decision back to the scenario; generic answers that could apply to any case study rarely earn top marks.
时间管理很重要：分配好阅读、规划、写作和检查阶段。考试中，要点列表和带注释的图表比长段落更快传递信息。在限时条件下练习历年WJEC案例分析以提升速度与信心。最后，每个决策都要与情境联系起来；适用于任何案例研究的泛泛而谈很少能得高分。
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