Although Grid technologies have matured considerably over the past few years, applications that can effectively utilize these technologies are far from ubiquitous.  Advances in Grid applications have simply not kept pace with advances in other aspects of distributed cyberinfrastructure, such as Grid middleware -- whether measured by the number of existing applications that can easily utilize the many advanced features offered by distributed infrastructure or measured by the number of novel applications capable of using the infrastructure. A key impediment in the accelerated development and deployment of Grid applications is the scarcity of high-level application programming abstractions that bridges the divide between the needs of Grid applications and the capabilities offered by middleware.