Within transmission models of communication, these terms are used to refer to the participants in acts of communication (communication being presented as a linear process of 'sending' 'messages' to a 'receiver'). Semioticians usually regard such models as reductionist (reducing meaning to 'content'); the main semiotic objection is usually that transmission models do not feature the semiotic concept of a code, but related objections refer to the model's neglect of the potential significance of purposes, relationships, situations and the medium.