Fig 1. Excerpt of the survey that was set up for the classification task.

The annotators were told to assign only one category per given artifact. If an artifact is a compound noun, the nested entities such as adjectives or second nouns that further describe the term were provided for tagging as well. In this question, ‘CO2 fixation’ is an example for a two term artifact and ‘groundwater’ an example for a one term artifact.