Explanation building is the inverse  starting with the observations, the evaluator develops a picture of what is happening and why.
( ( ( Explanation building ) ( is ( ( the inverse ) ( starting ( with ( the observations ) ) ) ) ) ) ( , ( ( the evaluator ) ( ( develops ( ( ( ( ( a picture ) ( of what ) ) ( is happening ) ) and ) why ) ) . ) ) ) )
(ROOT (S (S (NP (NN Explanation) (NN building)) (VP (VBZ is) (NP (NP (DT the) (NN inverse)) (VP (VBG starting) (PP (IN with) (NP (DT the) (NNS observations))))))) (, ,) (NP (DT the) (NN evaluator)) (VP (VBZ develops) (SBAR (SBAR (WHNP (NP (DT a) (NN picture)) (WHPP (IN of) (WHNP (WP what)))) (S (VP (VBZ is) (VP (VBG happening))))) (CC and) (SBAR (WHADVP (WRB why))))) (. .)))
Observations are the starting point when explanation building.
( Observations ( ( are ( ( the ( starting point ) ) ( when ( explanation building ) ) ) ) . ) )
(ROOT (S (NP (NNS Observations)) (VP (VBP are) (NP (NP (DT the) (JJ starting) (NN point)) (SBAR (WHADVP (WRB when)) (S (NP (NN explanation)) (VP (VBG building)))))) (. .)))