Serlet says he "wants to focus less on products and more on science." He's being replaced by Craig Federighi, who's currently VP of Mac Software Engineering, and, according to the press release, is "responsible for the development of Mac OS X and has been managing the Mac OS software engineering group for the past two years." What does the departure of the architect behind OS X mean for the future of Steve Jobs's company?
Serlet's work history includes a PhD in computer science from Orsay University, four years at Xerox PARC, then eight years at NeXT--the innovative computer company Steve Jobs headed during his years after being ousted from Apple. According to Apple, Serlet was responsible for the "definition, development and creation of Mac OS X" which is the "world's most advanced operating system"--a contentious description, but one that fits Serlet's academic background.
Most interesting is Serlet's time at Xerox PARC since, if you're a fan of Apple history, you'll know that Apple's original Mac computer was heavily inspired by projects that the research facility openly shared with Steve Jobs and his colleagues. Among other things, it's where the graphical user interface really came from. At NeXT, Serlet helped develop the workspace manager in NeXTSTEP--a key part in the object-orientated multitasking OS that set Steve Jobs' NeXTcube apart from peer workstations in the 1990s. When he joined Apple, Serlet helped port core elements of NeXT's operating system into Mac OS X. He was labeled  as a "friendly cyborg" by FakeSteveJobs, and is slightly famous for his appearance on stage at WWDC 2006, where he poked fun at Windows Vista's various failings as part of Jobs's famous "Redmond, start your photocopiers" schtick.
Federighi also worked at NeXT, then Apple, and then spent ten years working in several roles (including VP of Internet Services and CTO) at Ariba, before returning to Apple in 2009.
Both men are steeped in the science and theory of advanced computer programming and interface design, but you may be tempted to think of Serlet as the more academic of the two. And here's where the future of Apple's computing may get interesting: Serlet is quoted as saying his successor "has done a great job managing the Mac OS team for the past two years, Lion is a great release, and the transition should be seamless."
Since he mentioned wanting to move away from "products," we speculate that Serlet may be feeling a shift in the way Apple uses its OS. After all, OS X Lion has already  had a lot  of limelight, and it's almost being promoted by Apple as a separate, tangible "product" that helps make Macs better than PCs--instead of an integral part of the Mac experience. Lion will also incorporate a lot  of design  cues and interface  architecture that's being adapted from the iOS project--something that's very different from Serlet's experience, and probably hasn't been under his purview at Apple. Perhaps this means Federighi is the more managerial chap who's better placed to preside over OS X's next stage in evolution, which could take it far away from the mechanical roots it had in NeXT code, and in which Serlet is a true expert.
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