Online assessment of dimensional numerical answers using STACK in science

In this article we report research into the computer representation and automatic assessment of expressions which are dimensional numerical quantities. We consider how machines represent and manipulate dimensional numerical data. Through action research we examine how students enter dimensional numerical data into a machine for online assessment, and examine the properties of such answers which practical teachers seek to establish. We consider the extent to which these properties can be established automatically, and report the outcomes of our action research: extensions to the STACK online assessment system which implement both syntactic and semantic layers to represent dimensional numerical quantities in a form suitable for online assessment.