In this chapter, we examine the history and theory underlying social tagging as annotation; firstly from the perspective of classification research (CR), and secondly from the perspective of knowledge representation (KR) and knowledge management (KM). Using the context meta-model of the annotation, we demonstrate that the model is adequately represented in existing KR theory; specifically, from the perspective of socially constructed meaning in community networks. Furthermore, this set of tagging representations - triadic networks of individual, object and annotation a?? are well-explored throughout the KR domain. In contradistinction to many commentators, we conclude that social tagging may effectively be explored via a multidisciplinary approach linking KR and CR creating an open domain network.