Adobe and Macromedia may support each other's file formats and share space on the desktops of graphics professionals, but they're now adversaries in court. When it comes to the user interface, what's mine is mine, says Adobe, which has filed suit in the US District Court of Delaware, charging Macromedia for patent infringement. The patent covers the company's tabbed palette, a user interface element in Adobe products like ImageReady 2.0 (part of Photoshop 5.5), according to Adobe representatives. Tabbed palettes can display multiple sets of information in the same area of the computer screen. They let users customize how they organize product functions within the busy graphics workspace. "We are taking this action now, after notifying Macromedia on several occasions that its products are infringing our patent," says Bruce Chizen, Adobe's president, in a company statement. "The remedy sought is straightforward: We ask them to stop infringing our patent." Adobe claims that competitor Macromedia uses the tabbed palette in products like Fireworks, a Web graphics production tool, and the recently announced Flash 5, Macromedia's popular Web design tool. The most recent and obvious examples are Macromedia's announcements in July 2000 of a new user interface, which is incorporated into Flash 5 and its entire product line, Chizen says. With Flash 5 scheduled to be available in September, Macromedia begins its efforts to create a common user interface across its product lines. Designers will immediately be comfortable working in Macromedia Flash 5 because of its familiar industry standard user interface, company representatives said at the announcement. Not surprisingly, Macromedia has issued a statement "categorically denying the claims made in the lawsuit Adobe filed over patent infringement." "We believe the claims made are without merit and that the patent was invalid because it was obtained by not disclosing relevant prior art," which is previous work of the same type, according to Macromedia. Macromedia says it told Adobe that the patent was invalid back in 1996, when Adobe representatives first contacted Macromedia with complaints of infringement. The company says it repeated its position when Adobe most recently contacted Macromedia about the patent in May of 1999. The patent in question is U.S. Patent No. 5,546,528, granted to Adobe in August of 1996. No hearing has yet been set. Macromedia and Adobe already share a host of graphics-savvy users: Adobe Illustrator competes with Macromedia FreeHand; Adobe GoLive squares off with Macromedia Dreamweaver; and Adobe LiveMotion vies against Macromedia Flash. Their products even share certain file formats. Adobe supports the Flash .swf format in many of its products, while Macromedia supports Photoshop files in Fireworks. Sharing interface designs, as this lawsuit suggests, is something else.