Versioning artifacts with NMaven

In a different thread, Shane wrote:

>You need to use w.x.y.z, but may append it with anything after a hyphen.
> For example. 2.0.0.0-SNAPSHOT or 1.3-alpha1 are both okay to use.

I found [1] which explains the w.x.y.z versioning, but how does nmaven
handle the version in the pom vs. the one in the assembly?  If w.x.y.z
is a requirement, then how does 1.3-alpha1 work?

[1] http://msdn.microsoft.com/en-us/library/51ket42z.aspx

Thanks,
--
Wendy