As described in the presentation of GAML, the hierarchy of species derives from a single built-in species called
agent. All its components (attributes, actions) will then be inherited by all direct or indirect children species (including
experiment), with the exception of species that explicitly mention
use_minimal_agents: true as a facet, which inherit from a stripped-down version of
agent (see below).
agent defines several attributes, which form the minimal set of knowledge any agent will have in a model.