There is a certain amount of work that goes into making copyright successful and just as with other works, copyright for computer programs prohibits not only literal copying, but also copying of "nonliteral elements", such as program's structure, sequence and organization. These non-literal aspects, however, can be protected only "to the extent that they incorporate authorship in programmer's expression of original ideas, as distinguished from the ideas themselves." In "Computer Associates vs Altai", the Second Circuit proposed the Abstraction-Filtration-Comparison test for identifying these protected elements. This test attempts to distinguish copyrightable aspects of a program from the purely utilitarian and the public domain.