In this paper we critically analyse fundamental assumptions underlying approaches to symbol anchoring and symbol grounding. A conceptual framework inspired by biosemiotics is developed for the study of signs in autonomous artificial sign users. Our theory of reference uses an ethological analysis of animal-environment interaction. We first discuss semiotics with respect to the meaning of signals taken up from the environment of an autonomous agent. We then show how semantic issues arise in a similar way in the study of adaptive artificial sign users. Anticipation and adaptation play the important role of defining purpose which is a neces-sary concept in the semiotics of learning robots. The proposed focus on sign acts leads to a se-mantics in which meaning and reference are based on the anticipated outcome of sign-based interaction. It is argued that such a novel account of semantics based on indicative acts of refer-ence is compatible with merely indicative approaches in more conventional semiotic frame-works such as symbol anchoring approaches in robotics.