The Cascalog system has combined the Cascading system for abstraction of advanced data processing on Hadoop and other systems, the Datalog declarative programming language that is well suited for expressing database queries in an abstract form, and the Clojure language to create a declarative language for queries that can be run on Apache Hadoop.
Puppet Labs is the developer of Puppet, software that applies declarative programming to the task of system administration of compute, network, and storage infrastructure in traditional data centers or in the cloud.