The major functions of a wireless sensor network (WSN) cannot be accomplished without collaboration among wireless sensor nodes. However, most of the work found in literature only focuses a specific type of collaboration, associated with the accomplishment of a certain task, such as: signal processing, routing, etc. In this paper, we present a graph-based model of collaborative work created specifically for WSNs, which allows for representing all the entities of the network. We also present the formalization of some entities of the model and its properties, as well as its XML representation. This model is being used as a basis for the development of a 3D awareness tool for WSNs.