What is the Abstraction–Filtration–Comparison (AFC) test?

A three-step method to judge software copyright claims: abstract the program, filter out unprotectable parts, then compare what remains for similarity.

Did the court protect only literal code?

No. The court said non-literal elements like structure, sequence, and organization can be protected if they reflect original expression, not ideas or standards.

Why didn’t OSCAR 3.5 infringe?

After a clean-room rewrite, the remaining similarities were too thin. The filtered comparison showed no substantial similarity in protectable expression.

Can a trade secret claim run with copyright?

Yes, if it relies on extra elements like breach of confidence or improper acquisition. Then it may avoid federal copyright pre-emption.

What’s the quick takeaway for exams?

Altai sets the AFC test and confirms protection for non-literal software elements, while allowing parallel trade secret claims with additional facts.

Computer Associates International, Inc. v. Altai, Inc. (1992)

Zero-AI, zero-plagiarism classroom-style explainer for students.

Court: 2d Cir. Year: 1992 Citation Software IP Trade Secrets Read: ~7 min

Author: Gulzar Hashmi · India · Published: 2025-11-01

CASE_TITLE

Computer Associates International, Inc. v. Altai, Inc. (1992)

Slug: computer-associates-international-inc-v-altai-inc-1992

Keywords

PRIMARY_KEYWORDS: software copyright; non-literal copying; AFC test

SECONDARY_KEYWORDS: trade secret; pre-emption; Second Circuit

Quick Summary

This case teaches how courts judge software copyright beyond literal code. The Second Circuit approved the Abstraction–Filtration–Comparison (AFC) test. First, strip out ideas, standards, and public-domain parts. Then compare what is left. Using this, the court said Altai’s cleaned version (OSCAR 3.5) did not infringe. It also said a trade secret claim can live alongside copyright if it asks about more than copying alone.

PUBLISH_DATE: 2025-11-01 AUTHOR_NAME: Gulzar Hashmi LOCATION: India

Issues

Can non-literal software elements (structure, sequence, organization) get copyright protection?
Can a trade secret misappropriation claim run with a copyright claim when extra wrongful acts are alleged?

Rules

Non-literal parts of software can be protected if they show original expression.
AFC test: (1) Abstraction; (2) Filtration of unprotectable elements; (3) Comparison for substantial similarity.
Trade secret claims may avoid pre-emption when based on extra elements like breach of confidence or improper acquisition.

Facts (Timeline)

CA builds CA-SCHEDULER for IBM mainframes. It uses an interface module called ADAPTER.

Altai hires Claude Arney, a former CA engineer familiar with ADAPTER, to help build compatibility code.

OSCAR 3.4 is written. About a third of ADAPTER’s code is reused.

CA sues for copyright infringement. Altai answers with a clean-room rewrite: OSCAR 3.5.

District court finds OSCAR 3.4 infringed but OSCAR 3.5 did not. It also pre-empts CA’s trade secret claim.

Appeal: Second Circuit adopts AFC, affirms no infringement for 3.5, and revives trade secret theory for further look.

Timeline graphic for events in Computer Associates v. Altai

Arguments

Appellant (Computer Associates)

OSCAR 3.4 copied ADAPTER’s protected expression.
Non-literal structure and design choices were taken.
Trade secret rights were breached through insider knowledge.

Respondent (Altai)

Many overlaps are ideas, industry standards, or dictated by systems—thus not protectable.
Clean-room OSCAR 3.5 removed tainted code.
Trade secret claim is pre-empted by copyright.

Judgment

The Second Circuit held: non-literal software elements can be protected. The court adopted the AFC test. After filtering, OSCAR 3.5 did not infringe. The trade secret claim could proceed if based on extra wrongful acts, so the pre-emption ruling was reversed in part and remanded.

Ratio Decidendi

Structure–Sequence–Organization (SSO) can reflect protectable expression.
Filter out ideas, methods, standards, efficiency constraints, and external factors.
Compare what remains for substantial similarity.
Parallel trade secret claims survive when anchored in separate wrongdoing.

Why It Matters

This case is the backbone of U.S. software copyright analysis. It guides courts and coders. It helps teams plan clean-room rebuilds. It also reminds companies that IP strategies may need both copyright and trade secret tools.

Key Takeaways

AFC is the test for non-literal copying in software.
Clean-room rewrites can cure tainted code.
Ideas, standards, and system constraints are not protected.
Trade secret claims can run with copyright if extra elements exist.
OSCAR 3.4 infringed; OSCAR 3.5 did not.

Mnemonic + 3-Step Hook

Mnemonic: A-F-C → Abstract, Filter, Compare.

Abstract: Break the program into levels.
Filter: Cut ideas, standards, and constraints.
Compare: Judge similarity of what remains.

IRAC Outline

Issue	Rule	Application	Conclusion
Are non-literal software elements protected?	AFC test; protect expression, not ideas/constraints.	Filter out unprotectable parts; compare SSO.	Yes, if protectable expression is substantially similar.
Does OSCAR 3.5 infringe?	Apply AFC to cleaned code only.	After filtration, similarities were thin.	No infringement for OSCAR 3.5.
Can trade secret claims coexist?	Allowed if based on extra wrongful elements.	Alleged use of insider knowledge/confidence.	Claim may proceed; not fully pre-empted.

Glossary

Non-literal copying: Taking structure or design choices, not exact lines of code.
Clean-room: A fresh build by a team shielded from tainted code.
Pre-emption: When federal copyright displaces overlapping state claims.