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This is an explanation of the xSGE's version numbering, in particular
how it indicates compatibility between various xSGE releases.

xSGE version numbers have two or three components.  The components are
the major version, the minor version, and the release version.

Two versions of xSGE packages with different major versions can be
expected to be incompatible.  For example, there is no guarantee that a
program designed for version 1.0 of an xSGE package will work on version
2.0 of the package.

A version of an xSGE package with the same major version number, but a
higher minor version number, than another version of the package can be
assumed to be backward-compatible.  This number is used to indicate
things like unintrusive feature additions and module additions.  For
example, it can be expected that a program designed for version 1.0 of
an xSGE package will work with version 1.1 of the package.

As a special exception, two versions of an xSGE package with the major
version number 0, but a different minor version number, can be expected
to be incompatible (i.e. the minor version number is treated as the
major version number).

The release version is used to indicate very small changes, such as
bugfixes.  In general, this should never break compatibility, unless a
program was depending on a bug in the package.
