Cascading is a Data Processing API, Process Planner, and Process Scheduler used for defining and executing complex, scale-free, and fault tolerant data processing workflows on an Apache Hadoop cluster. All without having to 'think' in MapReduce.
Cascading is a thin Java library and API that sits on top of Hadoop's MapReduce layer and is executed from the command line like any other Hadoop application.
As a library and API that can be driven from any JVM based language (Jython, JRuby, Groovy, Clojure, etc.), developers can create applications and frameworks that are "operationalized". That is, a single deployable Jar can be used to encapsulate a series of complex and dynamic processes all driven from the command line or a shell. Instead of using external schedulers to glue many individual applications together with XML against each individual command line interface.
The Cascading API approach dramatically simplifies development, regression and integration testing, and deployment of business critical applications on both Amazon Web Services (like Elastic MapReduce) or on dedicated hardware.
Cascading is not a new text based query syntax (like Pig) or another complex system that must be installed on a cluster and maintained (like Hive). But Cascading is both complimentary and a valid alternative to either application.