Assessing Problem Decomposition in CS1 for the GenAI Era

TL;DR

The paper addresses teaching problem decomposition in CS1 within a GenAI-enabled era, proposing scaffolded Question Suites and code-free Decomposition Diagrams to assess architectural thinking. It details a course redesign that integrates decomposition from early weeks, explains the learning objectives (balancing trade-offs, problem-solving stages, abstraction, and novel-context reasoning), and presents iterative refinements to manage cognitive load. Key contributions include the Question Suite framework, an example Circular Color Pop scenario, and diagrammatic decomposition tasks used in labs and exams, along with reflections and future directions for scalable assessment. The work offers practical guidance for educators to cultivate robust architectural reasoning in beginners, ensuring decomposition remains central as GenAI tools become commonplace in programming work.

Abstract

Problem decomposition--the ability to break down a large task into smaller, well-defined components--is a critical skill for effectively designing and creating large programs, but it is often not included in introductory computer science curricula. With the rise of generative AI (GenAI), students even at the introductory level are able to generate large quantities of code, and it is becoming increasingly important to equip them with the ability to decompose problems. There is not yet a consensus among educators on how to best teach and assess the skill of decomposition, particularly in introductory computing. This practitioner paper details the development of questions to assess the skill of problem decomposition, and impressions about how these questions were received by students. A challenge unique to problem decomposition questions is their necessarily lengthy context, and we detail our approach to addressing this problem using Question Suites: scaffolded sequences of questions that help students understand a question's context before attempting to decompose it. We then describe the use of open-ended drawing of decomposition diagrams as another form of assessment. We outline the learning objectives used to design our questions and describe how we addressed challenges encountered in early iterations. We present our decomposition assessment materials and reflections on them for educators who wish to teach problem decomposition to beginner programmers.

Figures (2)

• Figure 1: Condensed version of the Circular Color Pop decomposition question. Students must identify which helper functions provide logical, appropriately-granular decomposition. Options A-C are correct; they encapsulate distinct computational steps (geometric setup, color transformation, and geometric condition checking).
• Figure 2: Diagrammatic decomposition question for the car simulator. Students must evaluate four architectural approaches, each representing different design trade-offs. Option C provides the best balance: clear two-level hierarchies under simulation_loop, with execute_command appropriately grouping the three player actions and check_end_conditions grouping the three termination checks.