Is a Qgis plugin that integrates with Postgres-Postgis database and allows versioning, user security administration and project management.
I was trained 18 years ago on SmallWorld GIS.
At that time Smallworld had a database technology with versioning capability called VMDS (Version Managed Data Store) and was unique at that time.
Versioning, allows multiple revisions of the data without duplicating all the data, or requiring different databases to be created.
As data Versioning showed to be very important, other vendors like ESRI-Arcgis implemented their own versioning system, with some similarities and differences.
But to be concise:
The concept of Version is analogous to the concept that has of drawing in a plane of paper. The creation of a version is analogous to the process of making a photocopy of the parent version. But once the photocopy is created the modifications in the original are NOT transferred to the copy and vice versa.
The only way to transfer the changes between two different versions, is through the "POST" function.
In the case of SmallWorld, it also has a “MERGE” function to transfer the changes between two different versions.