Ant is an open tool that the DITA Open Toolkit uses to manage builds.
Ant is a Java-based, open source tool provided by the Apache Foundation to declare a sequence of build actions. It is well suited for development builds as well as document builds. The "Full Easy Install" version of the toolkit ships with a copy of Ant.
DITA provides a set of XSLT scripts for producing different types of documentation, such as help output in Eclipse, Java Help and HTML Help, XHTML pages, and PDF. The DITA-OT uses Ant to manage these scripts, as well as to manage additional intermediate steps written in Java.