Annotations played a major role in Classics since the very beginning of the discipline. Some of the first attested examples of philological work, the so-called scholia, were in fact marginalia, namely comments written at the margins of a text. Over the centuries this kind of scholarship evolved until it became a genre on its own, the classical commentary, thus moving away from the text with the result that philologists had to devise a solution to linking together the commented and the commenting text. The solution to this problem is the system of canonical citations, a special kind of bibliographic references that are at the same time very precise and interoperable.
In this paper we present HuCit, an ontology which mod- els in depth the semantics of canonical citations. Its main goal is to underpin a Knowledge Base providing the information that an automatic expert system requires in order to read and interpret correctly this type of citations. Finally, we describe how HuCit can be combined together with the OAC ontology to publish in a semantic format a specific kind of machine-generated annotations, that is annotations concerning the canonical citations contained in secondary sources (e.g. journal articles, commentaries, etc.).