Sound Notional Machines

Staff - Faculty of Informatics

Date: 28 September 2023 / 15:30 - 18:00

USI East Campus, room C1.04

You are cordially invited to attend the PhD Dissertation Defence of Igor Moreno Santos on Thursday 28 September 2023 at 15:30 in room C1.04 (USI East Campus).

A notional machine is a pedagogic device that abstracts away details of the semantics of a programming language to focus on some aspects of interest. A notional machine should be sound: it should be consistent with the corresponding programming language, and it should be a proper abstraction. Notional machines found in the computer science education literature are usually not evaluated with respect to their soundness. To address this problem, we first introduce a formal definition of soundness for notional machines. The definition is based on the construction of a commutative diagram that relates the notional machine and the aspect of the programming language the notional machine is focused on. Leveraging this formalism, we present a methodology for constructing sound notional machines and a similar methodology to reveal potential inconsistencies in existing notional machines. We apply these methodologies to build sound-by-construction notional machines and find inconsistencies in existing ones as well as propose solutions to these inconsistencies. Finally, we show that the same commutative diagram that describes a notional machine can be used also to design experiments to evaluate that notional machine as an educational assessment instrument.

Dissertation Committee:

  • Prof. Matthias Hauswirth, Università della Svizzera italiana, Switzerland (Research Advisor)
  • Prof. Antonio Carzaniga, Università della Svizzera italiana, Switzerland (Internal Member)
  • Prof. Patrick Thomas Eugster, Università della Svizzera italiana, Switzerland (Internal Member)
  • Prof. Johan Jeuring, Utrecht University, Netherlands (External Member)
  • Prof. Tobias Wrigstad, Uppsala University, Sweden (External Member)