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GCN Home > August 22, 1995 issue

NT is Posix-compliant, GSBCA decides; ruling raises questions

By Shawn P. McCarthy

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All operating systems certified as Posix-compliant ought to be equal. But some, as George Orwell might say, are more equal than others.

A recent ruling by the General Services Administration Board of Contract Appeals affirmed the Posix compliance of Microsoft Corp.'s Windows NT operating system.

Several months ago, the National Institute of Standards and Technology certified NT as complying with the Posix standard, Federal Information Processing Standard 151-2 for open operating systems. However, C3 Corp. and Tisoft Inc. protested loudly when Unisys Corp. bid NT on the Coast Guard's Standard Workstation III procurement and won.

C3 and Tisoft insisted NT doesn't comply with all the mandatory requirements for Posix. The protesters were overruled. GSBCA said NT "is either compliant or met the government's requirements for this contract,' said Steve Meltzer, director of GSA's Federal Computer Acquisition Center, which made the award to Unisys.

The decision has raised questions about the role of Posix certification in federal procurements, as new operating systems like NT challenge the scope of NIST's test suite. Posix, a portable interface, defines the interactions between an operating system and its applications.

It's widely considered to be nearly synonymous with Unix, but now that linkage has been severed. "When people specify Posix, they need to be very specific,' said Martha Gray, a computer scientist who administers NIST's Posix testing program.

NT might meet the technical specifications for Posix compliance, she said, but it doesn't support optional Posix features such as graphical terminal interfaces, modem controls, mountable file systems and appropriate privileges.

Gray said she's worried that many procurement managers don't understand all these ramifications when they specify the level of Posix compliance for certain tasks.

In the Coast Guard workstation protest, C3 and Tisoft complained that NT didn't pass the main Posix tests cleanly. This too is a hazy area.

NT contains what is known as a Posix subsystem. Is that actually part of the operating system, or is it separate? GSBCA says it's included. NIST doesn't attempt to define what an OS must include.

"If you run the test suite and pass everything, you're in business,' said Roger Martin, NIST's chief of systems and software technology. "But you might get what's called a false negative.'

A false negative, as opposed to an actual failure, occurs when the NIST test suite doesn't clear a tested system in every area and can't indicate plainly what the problem is.

One reason: The standard itself might not be measuring the right things for every system. In that case, NIST can issue what's known as a resolve test code. It's not fair to say the OS had "a true pass,' Martin said. "I think the correct wording would be, "This test did not fail.' '

For example, say a system is being tested for black-and-white output. NIST's testers might report failure if it outputs shades of gray, because the test suite doesn't recognize grayscale as a form of black and white.

The testers then could pass the product with a resolve test code that competing vendors could use to challenge the legitimacy of the certification. Such situations are difficult to settle, because the distinctions are minute.