In the last few years, with the support of new communications and mobile technologies, Physical Annotations (PAs) have become popular in context-aware systems and pervasive computing. PA aims to enrich physical entities around us with useful information. Users can interact with inanimate objects, annotate them and share annotations with others. It helps daily life in different aspects, such as tourism, education and health. In this paper, we provide a formal model and theoretical concepts for PA systems. We also propose a new location model called DPVW-model for annotated entities. DPVW-model represents aspects of the annotatable physical world as well as the virtual domain. Then, we discuss the implementation and usability study of our system. Finally, we compare it with other similar systems.