CAFÉ, an automated feedback tool to approach Formal Methods

2026-07-03

AI Summary

This study addresses the challenge computer science students face in transitioning from operational to structural thinking and in mastering the construction of loop invariants within formal methods. To this end, it proposes a Graphical Loop Invariant-Based Programming (GLIBP) approach that guides learners to first model problems using graphical loop invariants (GLIs) via block diagrams and then derive code from these representations. The work introduces, for the first time, an integrated consistency analysis and automated feedback mechanism that jointly evaluates GLIs and their corresponding code. The accompanying educational tool not only provides personalized guidance to students but also assists instructors in designing programming assignments, thereby significantly enhancing students’ comprehension and application of formal methods.

Abstract

We present CAFÉ, a learning platform designed to introduce computer science students to Formal Methods (FM). CAFÉ aims to scaffold students' structural thinking (in contrast with operational thinking) by promoting the practice of Graphical Loop Invariant Based Programming (GLIBP). In the GLIBP approach, students solve loop-based problems by first constructing a Graphical Loop Invariant (GLI) before deriving the corresponding code. The GLI is an informal diagrammatic representation of the loop invariant. It illustrates the variables involved in the loop, their properties, and the relationships between them. To enable automated feedback, students complete a blank GLI, a box-based version of the GLI. Beyond evaluating the code students submit, CAFÉ provides personalized feedback on students' GLI and its alignment with the code. In this demo, we walk through CAFE from both a student's and a teacher's perspective. We show how the tool supports GLI design and provides feedback. We then present how a teacher can encode programming challenges together with a corresponding blank GLI.

Problem

• Formal Methods
• Structural Thinking
• Loop Invariant
• Automated Feedback
• Programming Education

Innovation

• Graphical Loop Invariant
• Formal Methods
• Automated Feedback
• Structural Thinking
• Loop Invariant Based Programming