As a professional courtesy, GAO will inform requesters of substantive media inquiries during an ongoing assignment.
( ( As ( a ( professional courtesy ) ) ) ( , ( GAO ( ( will ( ( inform ( requesters ( of ( substantive ( media inquiries ) ) ) ) ) ( during ( an ( ongoing assignment ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN As) (NP (DT a) (JJ professional) (NN courtesy))) (, ,) (NP (NNP GAO)) (VP (MD will) (VP (VB inform) (NP (NP (NNS requesters)) (PP (IN of) (NP (JJ substantive) (NNS media) (NNS inquiries)))) (PP (IN during) (NP (DT an) (JJ ongoing) (NN assignment))))) (. .)))
During an ongoing assignment, GAO will inform requesters of substantive media inquiries. 
( ( During ( an ( ongoing assignment ) ) ) ( , ( GAO ( ( will ( inform ( requesters ( of ( substantive ( media inquiries ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN During) (NP (DT an) (JJ ongoing) (NN assignment))) (, ,) (NP (NNP GAO)) (VP (MD will) (VP (VB inform) (NP (NP (NNS requesters)) (PP (IN of) (NP (JJ substantive) (NNS media) (NNS inquiries)))))) (. .)))