Annotating refers to the activity of making information about a digital object explicit by adding, e.g., comments, metadata or keywords to a digitized representation or to an annotation file associated with it. This can be in the form of annotations that comment on or contextualize a passage (explanatory annotations) in order to make structural or linguistic information explicit (structural/linguistic annotation), as linked open data making the relationships between objects machine-readable, or, in the case of general metadata, adding information about the object as a whole. Encoding is a technique associated with annotating, as are POS-Tagging, Tree-Tagging, and Georeferencing.