plot explanation - How does the dream sharing actually work?

In href="http://www.imdb.com/title/tt1375666/">Inception,
dream-sharing is (obviously) a huge part in how the entire plot
functions.

Is there any valid references (either scientific
or even just an explanation from the writers/director) as to how it is possible for
multiple people to share a dream in order to perform the simulations (the birth of
dream-sharing in the military training exercise) and
extraction?

Is this based on actual science related to
lucid dreaming or something of the like?

Or is this whole
dream-sharing business expected to be taken as a simple plot
device?

Answer

The film inception isn't really about dream sharing, and
while your question asks if it's possible I think that part is mostly fiction. While we
might be able to one day visualize dreams on a monitor while they happen, transferring
and connecting two or more people to a host's dream is purely science
fiction.

Still, the film is about planting ideas via one's
dream. Using their subconscious to control their waking behavior. That part of the film
is very plausible.

There are many psychology tests that
measure's a persons ability to recall information from memory. When it comes to
recalling information after a long period (several days) this is greatly improved if the
information is studied just before a REM sleep cycle. If the person studies the
information, sleeps and fails to dream, then recall performance is
reduced.

There is a connection between the development of
long term memories and dreaming. Which raises the question, can you introduce new
memories during a dream cycle? Yes, I think you can or at least it's a very popular
myth.

href="http://dreamscience.org/idx_science_of_dreaming_section-1.htm"
rel="noreferrer">More info here.

So to answer
your question, the plot of the film is plausible, the technique used in the film is
not.