Which Version of Version?

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As developers, I think we tend to take the definition of Version for granted.  What are the components of a version?  Well that's easy, it is:

Major.Minor.Build.Revision

Where the Build and Revision numbers are optional.  At least that is the definition given my the MSDN documentation for the Version class.

But look up Version in Wikipedia and you get a different answer.

The most common software versioning scheme is a scheme in which different major releases of the software each receive a unique numerical identifier. This is typically expressed as three numbers, separated by periods, such as version 2.4.13. One very commonly followed structure for these numbers is:

major.minor[.revision[.build]]

or

major.minor[.maintenance[.build]]

Notice that this scheme differs from the Microsoft scheme in that it places the build number at the very end, rather than the revision number.

Other versioning schemes such as the Unicode Standard and Solaris/Linux figure that three components is enough for a version with Major, Minor, and Update (for Unicode Standard) or Micro (for Solaris/Linux).

According to the MSDN documentation, the build number represents a recompilation of the same source, so it seems to me that it belongs at the end of the version, as it is the least significant element.

In Subtext, we roughly view the version as follows, though it is not set in stone:

  • Major: Major update.  If a library assembly, probably not backwards compatible with older clients.  This would include major changes. Most likely will include database schema changes and interface changes.
  • Minor: Minor change, may introduce new features, but backwards compatibility is mostly retained.  Likely will include schema changes.
  • Revision: Minor bug fixes, no significant new features implemented, though a few small improvements may be included.  May include a schema change.
  • Build: A recompilation of the code in progress towards a revision.  No schema changes.

Internally, we may have schema changes between build increments, but when we are prepared to release, a schema change between releases would require a revision (or higher) increment.

I know some developers like to embed the date and counter in the build number.  For example, 20060927002 would represent compilation #2 on September 27, 2006.

What versioning schemes are you fans of and why?

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