1. A method comprising: retrieving, from a server computing device, code to generate a web page on a client computing device, the code for the web page comprising: data representing a hierarchy stored on the server computing device, with modifications to the data being in accordance with local rules included in the code for the web page, with one or more remote rules that are stored on the server computing device, and with the one or more remote rules defining acceptable modifications to the hierarchy; receiving, by the client computing device, instructions for a modification to the data; verifying, in real-time by the client computing device, that the modification to the data complies with the local rules; sending, from the client computing device to the server computing device, a request to determine whether the modification complies with the one or more remote rules of the hierarchy; verifying, in real-time by the client computing device based on data received from the server computing device in response to the request, that the modification complies with the one or more remote rules that are stored on the server computing device; and causing, by the client computing device based on verifying, the server computing device to update the hierarchy with the modification.