The OT/J builder is a seamless extension of the Java builder for Object Teams. It manages the incremental compilation of individual source files within a project, which aims at performing minimal work only, as to speed up compilation for large projects if only small changes have been performed.
By the introduction of role files ( 1.2.5) even inner classes (here: roles) can be compiled individually. Incremental compilation is guided by an analysis of the various dependencies among classes.
If for some reason incremental compilation fails were it should not, a full build can be triggered by Project->Clean....
Note that the produced class files contain standard Java byte code. However, for execution the Object Teams Runtime Environment (OTRE) is needed in order to weave aspect code into base classes. Additional options in the launching dialog will take care of this detail for you (see Running Object Teams programs).