1. A method implemented by data processing apparatus, the method comprising: obtaining a model of a building wherein the model comprises a representation of the building at a point in time in construction of the building, and wherein the model contains a plurality of building objects that are indicated as being present in the building at the point in time by a construction schedule; processing the plurality of building objects including for a given building object of the plurality of building objects, identifying candidate edges of the given building object, wherein a candidate edge is an outer edge of a slab building object, an edge of an opening in a slab building object, or a lower edge of an opening in a wall building object, and processing the candidate edges to locate dangerous edges, wherein a dangerous edge is a candidate edge that is accessible and presents a risk of falling; wherein processing the candidate edges includes: identifying a protected edge, wherein the protected edge is a respective candidate edge having a first virtual box containing a protection object that minimizes or removes the risk of falling associated with the respective candidate edge based on a position of the protection object and the respective candidate edge, wherein the first virtual box is positioned partially on an interior side of the respective candidate edge and partially on an exterior side of the respective candidate edge, a bottom face of the first virtual box is a protection height beyond the respective candidate edge, and an outward-facing wall of the first virtual box is on the exterior side of the respective candidate edge and is offset a gap distance from the respective candidate edge; eliminating the identified protected edge from the candidate edges of the given building object forming a modified candidate set; and locating dangerous edges in the modified candidate set; and generating, by one or more processors, a presentation of the building based on the model of the building wherein one or more of the located dangerous edges are emphasized in the presentation.