code: public PrecompileDef createPrecompile() throws BuildException {
      final Project p = getProject();
      if (isReference()) {
        throw noChildrenAllowed();
      }
      final PrecompileDef precomp = new PrecompileDef();
      precomp.setProject(p);
      this.precompileDefs.addElement(precomp);
      return precomp;
    }
docs: Specifies precompilation prototype file and exclusions.