[erlang-questions] BEAM file forwards/backwards compatibility

[Bernie Duggan]

Hi all,
A thread from earlier this year makes it clear that BEAM files are
what I'll call "forwards compatible" for, nominally, 2 major versions.
For example, beams compiles with R9 will run on R10 and R11. All
great.
My question, then, is what about "backwards compatibility"?
Empirically, it appears that even minor release difference (compiled
on R14B04 and attempting to run on R14B03) are enough to cause a file
to be unable to be loaded , producing the error:

{'cannot load',<some module>,get_file}

Is this actually the expected behaviour, or should I be looking
elsewhere for the cause of this problem? (If it's expected, no big
deal, just as long as I know :)).

Cheers,

Bernard