Dryad was a research project at Microsoft Research for a general purpose runtime for execution of data parallel applications. Microsoft made several preview releases of this technology available as add-ons to Windows HPC Server 2008 R2. However, in October 2011, Microsoft discontinued active development on Dryad, shifting focus to the Apache Hadoop framework. There exist several high-level language compilers which use Dryad as a runtime; examples include Scope (Structured Computations Optimized for Parallel Execution) and DryadLINQ.