OK! I give up.
1) What is an endpoint?
Once I know that I will know what a capability or an IPC endpoint is.
If you have a look at "Distributed Systems: Principles and Paradigms"
by Andrew S. Tanenbaum and Maarten Van Steen, you will find a few pages
detailing what endpoints and capabilities are.
Also, Tanenbaum's book has all sorts of topics in it that discuss some
of the issues we are discussing on this list right now. However,
since distributed systems research is still relatively new (at least in
the areas we are concerned), the book leaves open questions for further
research; luckily, Tanenbaum cites well and links to lots of useful
papers in his book. The downside of the book is that it is 100
USD for a new copy.