sdd:replaces
sdd:replaces is the replacement record a datum line's %"old"/"new" form materializes — a predicate on a sdd:Datum, object a blank node carrying sdd:suppressed and sdd:displayed. It ties the value the source states to the value the diagram shows instead.
Unlike a sdd:Suppression's value-only omission (%"old" with no replacement), a sdd:replaces always pairs the suppressed value with a displayed one — the record is what carries the tweak, not the datum's sdd:value cache alone. If the source stops stating the suppressed value, the record has nothing left to justify the display divergence against — a dangling tweak (design spec §3.6): the shape that makes this checkable is exactly the two-sided record a sdd:replaces provides.