In the parlance of photography enthusiasts a Soft Lens is not a good lens. It is a lens that is not as sharp as one would like, sometime a lens is getting soft at the edges, and that's not a good thing too.
But now we are seeing more and more lenses that are computers with some glass on it. And that is giving the word "soft" a different interpretation.
This is the case of this news: Sigma has announced a software update to their tele-zoom 150-600 lens that will result in faster focussing, up to 50% faster (that's quite a lot!).
You just need to download the new software on your lens, using the Sigma USB dock.
What fascinates me is the transformation of "hard" products into "soft" ones. This is also enabling the transformation of products into services enabling new biz models. I see no reasons why companies like Sigma, as well as third party, would not start selling specific (software) add ons to their lenses to make them better fitting a given shooting session...
Software might also be used to decrease the "softness" of a lens by micro adjusting the focus in consecutive shots and combining the sharper parts together (that would work for standing still subjects...).
Interesting perspectives openend up by the digitalisation and softwarisation of our world.