replacing tiles is considerably simpler than onboard compilation or employing a look-aside store. however, it may not be efficient for transmission. a local change to entities and attributes, regardless of the extent, requires the transmission of the entire containing tile. furthermore, there are edge effects in which a change in an entity within one tile affects the entities in neighboring tiles. it is quite possible that a small number of entity changes will require the transmission of almost all tiles, thereby defeating the purpose of incremental updates. these problems can be addressed by selecting the tile size and the frequency of updating.