Sun Microsystems lawyer Rusty Day was grilled by an appeals court judge during his half hour-long hearing on whether the court should support a decision requiring Microsoft to carry Sun's Java in its products.

Microsoft's lawyer David Tulchin endured just a handful of questions from the judges, according to Microsoft and Sun officials present at the hearing.

Officials present at yesterday's Appeals Court hearing said Judge Paul Niemeyer, one of three judges hearing the case, peppered Day with questions about why Sun needs the Java "must-carry" order. Niemeyer asked questions about how Microsoft's monopoly in the operating system market affects the applications development platform, where Java competes with Microsoft's .Net, and about the economic theory of "tipping," in which a product's momentum quickly make it the overwhelming market leader.

Sun has argued that Microsoft has used its operating system monopoly to distribute versions of Java incompatible with Sun's and will use that advantage to distribute .Net. The .Net software family is a series of programs and development tools designed to allow users to build interoperable applications on the Internet.

But Niemeyer, at one point in the hearing, said the economic theory "doesn't make much sense," according to a witness at the hearing.

One witness described Sun's portion of the hearing as more of a conversation between Niemeyer and Day than a presentation from the lawyer.

The hearing is part of Microsoft's appeal of District Court Judge Frederick Motz's ruling December 23 that the company must include the Sun version of Java in Windows XP and on download sites. On February 3, the appeals court delayed the Java "must-carry" preliminary injunction from Motz, who is presiding over a number of private antitrust lawsuits against Microsoft in his Baltimore courtroom. Motz had set the clock ticking on the Java order in a ruling January 21, when he gave Microsoft 120 days to comply.

Lisa Poulson, a spokeswoman for Sun, said the appeals court has put the case on an expedited schedule, and could make a decision within 60 days: "There was a lot of active questioning," she said of Thursday's hearing. "We look forward to seeing what the result is."

Sun has argued that Microsoft tried to derail a competitive threat posed by Java by offering a version of the technology that is incompatible with Sun's specifications. Its lawyers argued before Motz that Microsoft's behavior, if allowed to continue, would unfairly drive developers to Microsoft's competing .Net platform.

Microsoft has argued that other issues, such as Java's performance and quality, have hampered developer adoption of Java, not Microsoft's actions. Its lawyers have argued that the "must-carry" Java order is an extreme solution to any competitive disadvantage Java has, and that Motz's order is unprecedented in antitrust law. Microsoft also has pointed to 2002 predictions from a number of industry analysts that say Java will continue to be the dominant developer platform.

Microsoft sees no imminent danger of the development platform market tipping away from Java before a full trial on Sun's complaints can be scheduled, said company spokesman Mark Murray. "We felt we were able to make our points effectively," Murray said of the hearing. "We felt it was an excellent hearing about the key issues in the case."