New science in many important disciplines now requires complex,
time-dependent access to distributed computing resources. We addresses
these problems by creating a higher level resource abstraction
that layers on top of existing Cyberinfrastructure that allows an application
to target stable resource aggregations spanning sites through
a well-defined and standard-compatible interfaces. The functionality of
vgES automatically maps application centric Virtual Grid specifications
onto available resources through a split-phase provisioning and actualization
protocol. Clients of vgES see all resources in terms of single resource
slot abstraction that can be treated as a form of advanced resource reservation
even when underlying resource do not support such reservations
directly.