  Grid infrastructures and computing environments have progressed significantly
in the past few years. The vision of truly seamless Grid usage relies on
runtime systems support that is cognizant of the operational issues underlying
grid computations and, at the same time, is flexible enough to accommodate
diverse application scenarios. This paper addresses the twin aspects of Grid
infrastructure and application support through a novel combination of two
computational technologies: Weaves - a source-language independent parallel
runtime compositional framework that operates through reverse-analysis of
compiled object files, and runtime recommender systems that aid in dynamic
knowledge-based application composition. Domain-specific adaptivity is
exploited through a novel compositional system that supports runtime
recommendation of code modules and a sophisticated checkpointing and runtime
migration solution that can be transparently deployed over Grid
infrastructures. A core set of "adaptivity schemas" are provided as templates
for adaptive composition of large-scale scientific computations. Implementation
issues, motivating application contexts, and preliminary results are described.
