Current solutions to characterize grid computing usage are limited in three important aspects. First, they do not provide a global, uniform view of the use of infrastructures comprised of heterogeneous grid middleware. Second, they do not allow the specification of policies to publicize the collected information. Third, they do not generate statistics about the applications that are executed on the grid. To fill this gap, we propose an architecture based on the Web Services Distributed Management standard and on access control policies to characterize global usage of grid computing infrastructures, even when such grids are formed by heterogeneous middleware packages. We introduce this architecture and present preliminary results obtained with a prototype.