A way of defining the main content of a genre that involves designating the classes of content associated with it (Stamatatos, Fakotakis, & Kokkinakis, 2002).
Stamatatos, E., Fakotakis, N., & Kokkinakis, G. (2002). Text genre detection using common word frequencies. International Conference on Computational Linguistics and The Proceedings of the 18th Conference on Computational Linguistics. 808-814.
Information scientists typically use the phrase "genre facets" when referring to texts specifically, though this use does not preclude other applications. They also use it to subcategorize texts for various purposes, such as search indexes.
Emerging Genres class, N.C. State University, Spring 2010