 It is, however, worth briefly mentioning some of the omissions that this brings with it. Various types of images have their place in science, and so do graphs, diagrams, and drawings. Perini (2010) and Elkins (1999) provide discussions of visual representation in science. Measurements also supply representations of processes in nature, sometimes together with the subsequent condensation of measurement results in the form of charts, curves, tables and the like (see the SEP entry on  measurement in science).  Furthermore, theories represent their subject matter. At this point the vexing problem of the nature of theories rears again (see the SEP entry on  the structure of scientific theories  and also Portides (2017) for an extensive discussion). Proponents of the semantic view of theories construe theories as families of models, and so for them the question of how theories represent coincides with the question of how models represent. By contrast, those who regard theories as linguistic entities see theoretical representation as a special kind of linguistic representation and focus on the analysis of scientific languages, in particular the semantics of so-called theoretical terms (see the SEP entry on  theoretical terms in science).