A city agency that put more than 400 HIV-positive foster children into clinical trials for AIDS drugs has asked for an independent review of the program after children’s rights advocates said it amounted to exploitation. John Mattingly, commissioner of the Administration for Children’s Services, said the inquiry would investigate whether the agency had the necessary permission from parents or guardians to include the children in the research from the late 1980s to 2001. The agency stressed that it does not believe there were ethical lapses, but it wants to make sure the program’s policies were proper and had been strictly followed.