There are different features of modelling problems (see summary by Maaß, 2010). In some
modelling problems, information that is important for solving a problem is missing, and
students need to make assumptions to solve this problem (Galbraith & Stillman, 2001). These
tasks may be called modelling problems with vague conditions (Schukajlow & Krug, 2014b).
Making assumptions is necessary for solving modelling problems with vague conditions and
sets this kind of problem apart from open-ended problems whose solutions may simply
involve providing samples such as a pair (1, 20) for the sum 21. Further, modelling problems
can contain information that students do not need to use to solve the problem, so-called
superfluous information