From time to time, the specification of Simple World can change. So, the versions of Simple World are numbered. The version number has two parts:

1. The version number is increased when a backward incompatible change is made in the specification.
2. The revision number is increased when a backward compatible change is made in the specification.

This means that bugs designed for a version or evolved in a version must work in all the future revisions of this specification version.

Versions should be source compatible, but this is not guaranteed. The source compatibility is only important for bugs developed, and not for bugs that evolve in the World because them can have mutations in their code.

At this time, there isn't a current version of the specification. 

The development version is the specification 1.0.