Ultra Dense Networks with flexible heterogeneous technologies (HetUDN) for the Radio Access Network (RAN) are prospective candidate architectures that promise to bring the required network flexibility and to support the transition to 5G networks. In the same time, Multi-access Edge Computing (MEC) is a recent paradigm shift that pushes the main focal point of mobile systems from centralized Mobile Cloud Computing (MCC) towards the network edge. Network softwarization enables the operation of new computational elements such as base stations and access points at the MEC, whereas edge computing, network control and storage promise to enable computation-intensive and latency-critical applications for resource constrained mobile devices. In this paper, we employ a novel disaggregated 5G architecture and apply a semantic-based coordination approach from the network edge. We consider semantics as the key enabling principle for the implementation of spectrum coordination schemes addressing the coexistence of heterogeneous technologies at the edge of 5G HetUDN wireless networks. A Semantic-based Framework for dynamic Spectrum Coordination (SFSC) deployed according to the MEC approach is proposed dealing with agile complex system resource management. Practical experimental evidence evaluated on a networking testbed is provided, proving that a semantic MEC middleware is capable of delivering novel advanced computation communication paradigms as needed for 5G networks.