A material, concrete object. Object An artifact or document that is matter of study. Source Event An event in time. Primary Source An artifact taht is considered to be a primary material in a given domain (e.g. wrote by the author(s) that is(are) matter of study). Person A human beeing. A concept, often an abstract thing, that is matter of philosophical studies. Rather than precisely define the concept, instances of this classes and of its subclasses are intended as 'topics', e.g. identifying generic aspects or areas in philosophical studies.. Concept A place, something that has a precised and fixed geographical position (a city, a building, etc.) Place Secondary Source An artifact that is considered to be secondary in a given domain (e.g. a commentary of a primary source wrote by a scholar). Fictional Entity Something that exists within a story, a literary work or a artwork in general. It can be a character of a movie (e.g. Batman), a place (e.g. Gotham City), a phisical object (e.g. the Bat-Mobile), etc. The author of a Source is the human being (Person) who produced it. has author has subject The subject of a Source can be a Concept, a Person, a Place or whatever the Source talks about or mentions. has part A source is part of an other source when it is a component of it. For example a chapter can be part of a book, a sentence can be part of an essay, a picture can be part of a page, etc. is part of