This paper presents an approach to dynamic public service mediation. It is based on a conceptual model and the use of search and ranking algorithms. The conceptual model is based on Abstract State Machine theory. Requirements for dynamic service mediation were derived from a real-world case. The conceptual model and the algorithms are developed and implemented by a proof of concept for this case. This model is build on existing means for sharing public services, which would enable migration of existing applications to our proposed approach. The conceptual model is compared to other models for service mediation to illustrate differences and identify similarities.