To this purpose, we conducted a systematic literature review finalized to presenting the ontologies, and the methods and technological systems where ontologies play a relevant role in shaping current smart  ...  We highlight those for which semantic technologies have been mostly demonstrated to be effective to enhance the smart city concept and, finally, discuss in more details about some open problems.  ...  AllergyLESS [100] is an intelligent recommender system aimed at reducing exposition time to allergens in smart cities by minimizing the exposure time of citizens to allergens during their walking routes  ...