Subject: Re: [Fwd: Re: I-D for the PATCH method]

From: Jim Whitehead <[email-masked]>
Date: Fri, 1 Sep 2006 11:21:36 -0700

Joe Feise writes:
> diff predates the FSF and GNU by a large margin.
> A quick search shows that the algorithm was implemented in the  
> early 1970s and
> described by James Hunt and Doug McIlroy in 1976 in a Bell Labs  
> tech report:
> http://www.cs.dartmouth.edu/~doug/diff.ps
> Bibtex reference (http://www.cs.dartmouth.edu/~doug/doug.bib):
> @techreport{McIlroy76b,
>    author = {J. W. Hunt and M. D. McIlroy},
>    title = {An Algorithm for Differential File Comparison},
>    institution = {Bell Laboratories},
>    address = {Murray Hill, NJ},
>    number = {CSTR 41},
>    year = {1976}
> }
>
> It is my understanding that what is now called "normal diff" was  
> the original
> implementation's output. Context and unified outputs were added later.

This is my understanding of this technical report as well.

While IANAL, even if there had been a patent filed on this technology  
in the mid-70's (and I'm pretty sure there was not), it would now be  
expired, since you have a year from public disclosure to file, and  
patent durations are 20 years from filing.

So, at least for normal diff, we have both a stable reference, as  
well as a pretty clear story on freedom from intellectual property  
restrictions.

- Jim

---

From: Jim Whitehead <[email-masked]>
Date: Fri, 1 Sep 2006 11:32:37 -0700

> Jim Whitehead didn't think that there would be any issue with the IPR
> requirements for the gdiff patch format. But if anyone knows  
> better, we'd
> like to know.

Specifically, we have public disclosure of GDiff in 1997 in:

http://www.w3.org/TR/NOTE-gdiff-19970901

A fairly brief search by myself of the US patent database (I am  
assuming that any patent application on this matter would have been  
approved by now -- the patent office is slow, but not that slow) was  
not able to find any patents on this difference format. This is  
somewhat consistent with the submission statement by Marimba:
http://www.w3.org/Submission/1997/11/

This states:

Marimba, Inc. agrees not to assert any Patent Claim against any third- 
party arising from the use, manufacture, sale, distribution, or  
implementation of any portion of any product, method, or procedure  
which is necessary to implement GDIFF. Patent Claim means claim(s) of  
a patent or patent application which are owned or controlled by  
Marimba, Inc. that must be infringed in order to make, use or  
implement a product, method, or procedure that implements GDIFF.

(Although this statement does suggest they had at least considered  
filing a patent.)

While IANAL, this appears to be a clear case of public disclosure,  
with no subsequent patent filing within a year of disclosure. As a  
result, I believe this technology is now public domain.

However, I note that there is some ambiguity concerning copyright of  
the specification, and so it would be best to limit the amount of  
text used verbatim from the GDiff specification.

- Jim