Definition:
An information content entity that is a mark(s) or character(s) used as a conventional representation of another entity.
Editor note:
20091104, MC: this needs work and will most probably change
Editor note:
2014-03-31: We would like to have a deeper analysis of 'mark' and 'sign' in the future (see https://github.com/information-artifact-ontology/IAO/issues/154).