Computer Associates Int'l, Inc. v. Altai, Inc., 982 F.2d 693 (2d Cir. 1992)
Computer Associates v. Altai is a foundational decision in software copyright law that reshaped how courts evaluate claims of non-literal copying—i.e., copying that does not reproduce source or object code verbatim but allegedly appropriates a program's structure, sequence, and organization.
How should courts determine whether a computer program infringes the non-literal elements of another, and to what extent are state-law claims such as trade secret misappropriation preempted by the Copyright Act when they arise from the copying of computer programs?
Non-literal infringement of computer software is assessed using the abstraction–filtration–comparison test: (1) Abstract the program into its constituent structural levels; (2) Filter out unprotectable elements, including ideas and processes (17 U.S.C. § 102(b)), elements dictated by efficiency (merger), external constraints (e.g., operating system requirements, hardware standards, industry practices, and compatibility mandates), materials from the public domain, and scènes à faire arising from standard programming practices; and (3) Compare the remaining protectable expression with the accused work for substantial similarity. Regarding preemption, 17 U.S.C. § 301 preempts state-law claims that assert rights equivalent to those protected by copyright; however, claims containing an extra element —such as breach of confidence or improper means in trade secret law—are not preempted because they are qualitatively different from a claim of mere copying.
The Second Circuit adopted the abstraction–filtration–comparison test and affirmed that OSCAR 3.4 infringed CA's copyrighted code through literal copying. It also affirmed that, after proper filtration, OSCAR 3.5 did not infringe CA's non-literal program elements. On preemption, the court held that state-law claims equivalent to copyright rights are preempted, but a trade secret misappropriation claim predicated on breach of confidence or improper means is not.
Altai is the leading case on non-literal software copyright infringement. Its abstraction–filtration–comparison test has been widely adopted because it operationalizes the idea/expression dichotomy for software and carefully cabins copyright to expressive choices rather than functional necessities. The decision also provides a clear framework for preemption analysis, distinguishing between preempted state claims that mirror copyright and non-preempted trade secret claims involving breach of confidence or other improper means. For law students, Altai is essential to understanding how courts balance innovation incentives with interoperability, efficiency, and competition in the software industry.