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Re: st: RE: About data transformation

From (Vince Wiggins, StataCorp)
Subject   Re: st: RE: About data transformation
Date   Fri, 14 Feb 2003 13:19:10 -0600

Patrick Joly <> suggests that it may be possible to save
a dataset in Stata 6 format from Stata 8,

> Humm, you mean that issuing
>         version 7.0: save filename6, old
> in Stata 8 will not yield the same result as issuing
>         save filename6, old
> in Stata 7?
> My understanding so far was that version control was designed to
> retain the functionality of earlier versions of Stata.

Interesting thought, but the answer is no.  

The goal of the -version- statement is backward compatibility -- that is to
say, the ability of new versions of Stata to run do- and ado-files written
with old syntax.  Stata's language is evolving and we sometimes make changes
that would cause old syntax to break or produce different results.  You don't
want your programs to break or your results to change; so, if you are using
Stata 8, you should put -version 8- at the top of your do-files, at the top of
your class-files, or right after the -program ...- statement of your
ado-files.  Stata's promise to you is that your do-file or program will
continue to work and produce the same results as new versions of Stata are
released.  It's not really a promise, we have occasionally made changes where
strict version control could not be maintained -- such as the introduction of
time-series operators in Stata 6 -- but such occasions are the exception.

What Patrick suggests, is forward compatibility -- the ability of a newer
version of Stata to mimic an older version -- and that is not something
provided under version control.  Sometimes forward and backward compatibility
mean the same thing, but not in this case.

-- Vince

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