Representing constraint problems visually

Student thesis: Doctoral Thesis (PhD)


With the increasing complexity of the world and the explosion of both information and choices, people are faced with having to make more decisions and solve more problems. One typical type of problem that people are confronted with during their daily lives is constraint problems. Common examples of such problems include scheduling, trip planning, table planning, or resource allocation. Existing constraint solvers can solve these kinds of problems quickly. However, to use these solvers requires knowledge of constraint programming languages, which require significant time and effort to learn, and one cannot expect the general public to learn these solvers.

To address this issue, I investigated how people visually represent constraint problems, gaining insight into common techniques that people use to represent this kind of problem. This initial study showed that people often used a variety of different modalities and approached the problem in a non-linear way.

From this study, a set of guidelines were developed for the design of visual constraints modelling languages. Using these principles, I designed a visual constraints modelling language. From this language, I designed and implemented a visual constraints modelling interface and system (Solvi), which can model various constraint problems and solve the problems using existing constraint solvers.

Both the language and interface were evaluated through a user study to understand how people visually modelled both predefined and their own constraint problems. This indicated that the developed visual language and interface can model common constraints problems. The positive feedback received confirms that the visual modelling language is useful for dealing with the problems encountered in daily life and the visual representation is easier for understanding the relationships between the elements. However, some issues were identified, and possible future improvements to the language and interface, and further research into problem modelling are also discussed.
Date of Award28 Nov 2023
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorMiguel Angel Nacenta Sanchez (Supervisor) & Ozgur Akgun (Supervisor)


  • Human-computer interaction
  • Visualisation
  • Constraint modelling
  • Visual modelling

Access Status

  • Full text open

Cite this