Publish-subscribe systems are defined by its communication model. However, most of the existent publish-subscribe systems incorporate other mechanisms in their implementation. This work seeks a better understanding of publish-subscribe systems, defining an architecture where different layers group related decisions and constructions. Based on this architecture, we describe a system developed in Lua that uses a distributed hash table as its base. The system differs in its architecture from monolithic publish-subscribe systems and focus on generality, flexibility and extensibility.