The Grid is a dynamic environment in which resources can quickly go from idle to busy state depending on application operations. In such a scenario, resources can be used more effectively by introducing reservation and allocation.As a solution, this paper proposes STREGA: a software architecture that handles resource reservation and greatly simplifies the integration of applications with a Grid environment. In it, resources needed by applications are automatically detected, and operations such as resource reservation and allocation are accordingly transparently performed e.g. using Globus services.Within STREGA, some components are aimed at understanding the needs of application classes, other components dynamically re-adapt resource requests on the basis of the observed application behaviour. Additional components are proposed to support reservation when this is unavailable from the underlying system (i.e. Globus and the OS).