the public domain rather than address the issue of SSO. Jaslow appealed the decision. The Court of Appeals for the Third Circuit noted that computer programs are literary works under U.S. law. The court reasoned that with literary works a non-literal element is protected to the extent that it is an expression of an idea rather than the idea itself. By analogy, the purpose or function of a software work would be the work's "idea", while everything not necessary to that purpose or function would be part of the expression of the idea. The expression would be protected, although the basic purpose or function would not. On this basis the Court of Appeals upheld the district court's ruling of copyright violation due to similarity of SSO. Early adoption and criticism For the next few years most, but not all, circuit courts accepted the Whelan decision on SSO in one form or another. This resulted in a period of tight protection for software, since almost everything other than the broad purpose of a software work would be protected. The only exception was where the functionality could only be achieved in a very small number of ways. In these cases there could be no protection due to the merger doctrine, which applies when the expression and the idea are inextricably merged. In one case a court found that a defendant had infringed the right to prepare a derivative work when they copied the sequence, structure, and organization of the plaintiff's file formats, screen, reports, and transaction codes, even though different data fields were present. In 1986 the ruling in Broderbund Software, Inc v. Unison World, Inc appeared to prevent software developers from marketing products with the same or similar user interfaces, regardless of whether there was anything in common in the underlying code. In the 1990 case of Lotus v. Paperback the U.S. District Court for Massachusetts decided that Paperback's VP-Planner software violated the copyright of Lotus's 1-2-3 spreadsheet program since it had the same user interface, even though the underlying code was completely different. A technical criticism of Whelan is that it fails to distinguish between the sequence in which instructions are presented in the text of a program and the sequence in which the instructions are executed - the program's behavior. Both the textual and behavioral aspects have their own SSO, but a programmer would see the textual SSO as