A system comprising at least one computer hardware processor; and at least one computer-readable storage medium storing processor-executable instructions that, when executed by the at least one computer hardware processor, cause the at least one computer hardware processor to perform: generating an object hierarchy comprising a plurality of objects corresponding to active graphical user interface (GUI) elements of at least one of a first application program and a second application program; controlling the first application program to perform a first sub-task of a task at least in part by using the object hierarchy; and controlling the second application program to perform a second sub-task of the task at least in part by using the object hierarchy, wherein the first and second application programs are configured to execute at least in part by using different GUI application libraries.