Re: ZFS

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

On Nov 8, 2009, at 12:42 PM, vincent wrote:

> Le 8 nov. 2009 à 18:33, Ty Sarna a écrit :
>
> > > Okay, it can be no more than a voyage back in time to the  
> > > aforementioned episode – so, is there any estimation as to the  
> > > percentage of Sun code in today's NetBSD ZFS port?
> >
> > What does that have to do with anything? It could be 100% NetBSD  
> > code and that wouldn't change anything as far as patents.
>
> I am not sure about this. I think you can't patent a concept, but  
> you could patent an implementation. For example, in the electronics  
> field, you maybe can patent a type of high-quality oscillator, but  
> you cannot claim any property on a different implementation  
> achieving the same goal. If you can code from scratch a FS with the  
> same functionalities as ZFS, I don't figure out how you could be  
> liable to patent suing.


That's not the way patents work.  What you've described is more like  
copyright, where the particular expression of the concept is  
protected.  With patents, it's the concept itself -- but details matter.

Let's consider the case of the famous (and now-expired) RSA patent: http://www.google.com/patents/about?id=daEsAAAAEBAJ&dq=4,405,829 
 .  Fundamentally -- and I believe this is true throughout the world,  
though what can be patented differs in different jurisdictions -- a  
patent consists of two parts, a description of the invention and  
"claims".  The description is just that: it describes how the  
invention works.  A patent is basically a deal between the government  
and an inventor: the inventor describes the idea in sufficient detail  
that others can replicate it, learn from it, etc.; in return, the  
government grants a limited-term monopoly on the *idea*.  Precisely  
what is protected is described by the claims.  You infringe a patent  
if you build something that contains all elements of any one claim.   
Thus, if you look at claim 1 of the RSA patent, to infringe you'd need  
a system with a communications channel, an encoder that worked  
according to that description, and a decoder that worked according to  
its description.  If you built a system that had no communications  
channel, you wouldn't infringe claim 1.  However, you might infringe  
claim 37, which doesn't speak of a channel.

There's a lot more I won't go into, like the "doctine of  
equivalents".  The net, though, is to the extent that the patent is  
valid in jurisdictions of interest, you can't evade it by changing  
code; you probably have to change functionality.

                --Steve Bellovin, http://www.cs.columbia.edu/~smb