Slides of the talk from the associated paper:

This paper discusses the nature of mathematical assessment, and compares paper-based learning materials with current online assessments. In the light of this comparison we propose a data structure for representing multi-part mathematical questions, which is a direct development of that currently implemented in STACK. STACK makes use of the computer algebra system Maxima for a variety of tasks, the most important of which is establishing mathematical properties of student's answers.

In this talk I will describe a computer aided assessment system for
mathematics known as STACK, a System for Teaching and Assessment using a
Computer algebra Kernel. STACK makes use of the computer algebra system
Maxima for a variety of tasks, the most important of which is establishing
mathematical properties of student's answers. We discuss STACK with a
focus on (i) the data structure used to represent questions, (ii) how
teachers write questions of their own and (iii) the characteristics needed
of a CAS for this application.

The STACK computer aided assessment system (http://www.stack.bham.ac.uk) uses the computer algebra system Maxima to automatically grade student's answers to mathematical questions, providing immediate feedback on the mathematical properties of their answers. The design philosophy; practical implementation; details of question authoring; and feedback from student users will be discussed.