In recent years, there is an increasing interest in the Semantic Web and the relevant technologies, which can have a significant impact in the context of information and knowledge management. An important observation is that the entity identification problem lies at the core of many semantic web applications and the intrinsic difficulties of this problem have hindered progress in this area. In this paper, we argue for an infrastructure responsible for assigning and managing unique identifiers for entities in the semantic web, and we propose a conceptual model for the storage and management of these entities. The proposed model is generic and flexible and it allows for efficient and effective retrieval and analysis of the stored entities. We discuss the requirements with respect to creating and modifying these entities, as well as to managing their evolution over time. Finally, we study some enhancements of the entity representation, and we discuss the beneficial impact they can h...