Understanding Query Plan

[Hancel Gonzalez]

Hi all, 

i get the query plan with the explain flag in this engine but i don't understand it, i.e., how to recognize the operators used in the query, for example, nested loop join or another. 

For example, see the next query: 

SELECT * 

WHERE 

{ ?x <http://xmlns.com/foaf/0.1/givenname> "Stephen" . 

  ?x <http://xmlns.com/foaf/0.1/interest> ?i 

} 

LIMIT 10

and its query plan is:

execute 0/2: 

triple(variable(x), uri<http://xmlns.com/foaf/0.1/givenname>, string("Stephen")) LIMIT 998

NNNNo (_,?,_[c620b0be6e4afc2c],_[63309410bc0df058]) -> 1

1 bindings (1)

execute 1/2: 

triple(variable(x), uri<http://xmlns.com/foaf/0.1/interest>, variable(i)) LIMIT 998

mmmms (_,?[e1a9cfba0bd28872],_[c544a39ca3c96008],?) -> 4

4 bindings (8)

How i interpret the above plan? Exists one manual with syntax for to undestand that o something? 

Many thanks. 

Regards, Hancel.