On Thursday, Google's Project Ara made an early version of its Module Developers Kit (MDK) available for download, offering a first glimpse at the company's bid to reinvent the mobile industry. Project Ara began as a Motorola Mobility project to create a modular smartphone. When Google sold Motorola to Lenovo, it retained Motorola's Advanced Technologies and Projects (ATAP) group, headed by Regina Dugan, former director of the US Defense Department's DARPA.

The MDK consists of the software and specifications necessary to begin designing Project Ara hardware modules. These modules will eventually fit together with other modules like Lego bricks. Users will assemble their modules on a frame called an "endo," short for "endoskeleton."

In theory, this will have several advantages over traditional smartphones. Mobile users will be able to customize their smartphones to meet their needs. They will be able to replace or upgrade individual components, with less expense and less electronic waste. They will also have access to a greater range of hardware enhancements than they would in a more closed ecosystem.

"This is a very early version, but our goals are to give the developer community an opportunity to provide feedback and input, and to help us ensure that the final MDK -- anticipated at the end of 2014 -- is elegant, flexible, and complete," said Paul Eremenko, head of Project Ara and another former DARPA executive.

In a recent interview with Time, Eremenko described Project Ara as a way to do for hardware what Android and other platforms have done for software. That should worry other mobile platform companies like Apple and Microsoft. What Android has done for mobile operating system software is sucked the value out of the market.

[From security to "Lego" programming, Android has a lot going for it. See 5 Ways Android Won Me Over.]

By offering Android free to mobile hardware makers, Google has made it difficult for Microsoft to charge for its Windows Phone mobile operating system. The company recently made Windows free on devices with screens smaller than nine inches. Apple doesn't charge for iOS, but its costs are built into its iOS hardware and ecosystem. Android's market-share gains will attract more third-party innovation, forcing Apple to invest and respond.

Though Apple remains immensely profitable, the company may not be able to maintain its margins in the face of open software and open hardware. Project Ara phones could end up competing at both the low end and high end of the market simultaneously. Apple is already expected to expand its mobile lineup to meet demand for more varied screen sizes. But shifting from two iPhone models to three or four isn't likely to hinder Android adoption if Project Ara can manage dozens of distinct variations and can make those variations appealing.

Worse still, if Project Ara works as conceived and slows the mobile hardware upgrade cycle, Apple customers could come to question the planned obsolescence that drives hardware upgrades. In 2010, JD Power found that smartphone owners on average kept their mobile devices 27.8 months. If Project Ara encourages people to hold on to their phones longer, mobile sales will suffer as module sales surge. Unless Apple can sustain the innovation necessary to stoke demand for new iPhone hardware -- an increasingly tough proposition as time goes on -- its smartphones are likely to match a smaller and smaller range of what the open Project Ara ecosystem can offer.

At the same time, Project Ara faces huge hurdles and a stumble could be damaging. The last thing Google wants to see is Apple marketing executive Phil Schiller standing on stage with a Project Ara-based Frankenstein phone that looks ghastly, devours battery power, baffles users, and ends up costing more than a sleek, stable iPhone. Software errors can be fixed without much trouble. Hardware problems present much more of a challenge.

Project Ara will depend on 3D Systems to offer on-demand manufacturing for module makers. Mass customization of electronics components has yet to be demonstrated. If it works, it could revolutionize electronics manufacturing. Why employ cheap labor abroad if robots can assemble your hardware?

Project Ara has a lot to prove. But what if the entire concept is already outdated? The notion that a smartphone must be a single unit seems like something out of the 1980s, when connection meant cabling and physical contact. In the wireless era, it may not be necessary to design smartphone modules so they can be physically connected. There may be reasons to do so -- access to a single power source, data transfer rates, data security, and manageability -- but there may also be reasons to make modules wireless and independent of a central spine. What is the Nike+ running sensor but a Bluetooth-based iPhone module? To put it another way, why design a Project Ara-specific module that's limited to Android when you could make a Bluetooth version that works with Android, iOS, and Windows Phone devices?

However Project Ara turns out, it's likely to have a positive effect on the mobile industry. It should encourage hardware and software makers to rethink what defines a smartphone. Since 2007, we've had the trinity as described by Steve Jobs: "a widescreen iPod with touch controls; a revolutionary mobile phone; and a breakthrough Internet communications device."

Beyond the mobile era, in the time referred to as the Internet of Things, a device can be all, some, none of these things, or much more. As long as the device can communicate with other systems, it hardly matters how the device is defined, since wireless connectivity makes that definition flexible.

The first Project Ara phones are expected early next year.

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