When a photograph documents a particular archaeological site, its PhotoRecord can carry a siteId pointing to that Site. This link is optional — a general project overview shot or a studio artifact photo may have no site at all — but when present it lets you pull up every image of a given site at once. Because the link is set to clear rather than delete the photo if the site record goes away, removing a Site never destroys the photographs that referenced it; their siteId is simply emptied.
Technical section
Data model, API, and internals — visible to developers.