i want to make an app which uses a map in such a way that places can be tagged(marked) on it and its reflected on the map i.e. it is synchronized and the update is visible to everyone accessing that map, also i want to make tagging of places restricted to a certain group of privileged people, i.e. only a certain category of people can tag places and the rest can only view the tagged(updated) places and not tag places. help me in this.