Jaql is a JSON-based query language that translates into Hadoop MapReduce jobs. JSON is the data interchange standard that is humanreadable like XML but is designed to be lighter-weight.

Jaql programs are run using the Jaql shell. We start the Jaql shell using the jaqlshell command. If we pass no arguments, we start it in interactive mode. If we pass the -b argument and the path to a file, we will execute the contents of that file as a Jaql script. Finally, if we pass the -e argument, the Jaql shell will execute the Jaql statement that follows the -e.

There are two modes that the Jaql shell can run in: The first is cluster mode, specified with a -c argument. It uses the Hadoop cluster if we have one configured. The other option is minicluster mode, which starts a minicluster that is useful for quick tests. The Jaql query language is a data-flow language.