A Representation Model represents a real or reconstructed state over a span of time — a photogrammetric scan of March 2016 is the best representation of the site from 2016 until, say, an earthquake changes it in 2018. Today that span is only implicit: an RM carries has_first_epoch (its start) and survive_in_epoch (the later epochs through which it survives), but there is no first-class, justified [start, end] and no record of why the representation stops being valid at a given moment.
DP-74 makes the validity delta first-class and, crucially, paradata-justifiable: the start and the end of an RM’s validity become boundaries an author can defend with a paradata chain (the 2018 earthquake, a demolition, a rebuild), exactly the kind of source-based reasoning EM is strongest at. The RM Manager gains the UI to set and edit these boundaries and to attach or inspect the justifying paradata.
This is also where the 3D layer meets the editing experience: editing an RM’s temporal validity, its transform and its paradata is the concrete case that motivates making the 3D-node part editable from EMStudio (DP-75), rather than only from Blender.
1.7
Needed (a site with a datable change — e.g. an earthquake)
Confirmed by E.D. 2026-07-30 ('assolutamente sì'). Verification: today the [start,end] delta is only implicit via has_first_epoch + survive_in_epoch epoch-membership edges, with NO explicitly justified boundaries — the 'delta from-to' is theoretical. This DP makes it real and paradata-backed. Tightly connected to the editing surface: E.D. wants the 3D-node part (RM/RMDoc/RMSF, transforms, validity) editable from EMStudio too — see DP-75.