Web Services SDK

I have a corporate portal and I am planning to write a code such that the users when they log in to the portal they are able to answer some prompts and then a report gets created using BO and the result is displayed as a graph. Now correct me if I am wrong please I am thinking to use web services SDK or Report Engine SDK kindly suggest which would be the best to use. And also is it actualy possible to get the result as a graph not as a table? I have gone through the samples but still wnted to get a second opinion.