Question about @base and relative IRI "resolving"

Fellows,

In case you can't tell from my prior unanswered question ( 
http://lists.w3.org/Archives/Public/public-linked-json/2014Nov/0004.html 
) I'm in the middle of a new JSON-LD processor implementation.

I have another question, this one about 3.4.4 of the Context Processing 
Algorithm ( 
http://www.w3.org/TR/json-ld-api/#context-processing-algorithm ). It 
says:

 3.4.4) Otherwise, if value is a relative IRI and the base IRI of result 
is not null, set the base IRI of result to the result of resolving value 
against the current base IRI of result.

My question is, what does "resolving" mean in that sentence?

We could have an @base in the result of "http://cnn.com/" for example. 
What should happen when the local context(s) provide relative @base 
IRI's of:

1) "/foo/bar"

2) "foo/bar" and then "blat/bloo"

Is #1 above a valid relative IRI? If so, is the new @base of result 
"http://cnn.com/foo/bar" or "http://cnn.com//foo/bar"?

For #2 where we have multiple local contexts to process, does this end 
up with the final @base in result as ""http://cnn.com/foo/barblat/bloo"?

Just looking for some definition of "resolving" in this (unusually) 
vague portion of the otherwise clear spec.

Oh… and if you're so inclined to weigh in on value expansion… I'd be 
much obliged: 
http://lists.w3.org/Archives/Public/public-linked-json/2014Nov/0004.html

Cheers,
Sean