This can be used to build subprojects. This task must not be used outside of a target if it invokes the same build file it is part of.

When the attribute is omitted, the file "build.xml"; in the supplied directory ( attribute) is used.

If no attribute is supplied, the default target of the new project is used.

By default, all of the properties of the current project will be available in the new project. Alternatively, you can set the attribute to and only "user" properties (i.e., those passed on the command-line) will be passed to the new project. In either case, the set of properties passed to the new project will override the properties that are set in the new project (See also the property task).

You can also set properties in the new project from the old project by using nested property tags. These properties are always passed to the new project and any project created in that project regardless of the setting of . This allows you to parameterize your subprojects. Properties defined on the command line cannot be overridden by nested elements.

References to data types can also be passed to the new project, but by default they are not. If you set the inheritrefs attribute to true, all references will be copied, but they will not override references defined in the new project.

Nested elements can also be used to copy references from the calling project to the new project, optionally under a different id. References taken from nested elements will override existing references that have been defined outside of targets in the new project - but not those defined inside of targets.