As tablets and smartphones become everyday business tools, smart IT leaders are moving from just accepting them to devising ways to fully support mobile business applications. For many IT organizations, that means jumping into the deep end of the pool by creating custom apps for both internal and external users. After all, if there's more than half a million apps on Apple's App Store, then most IT organizations should be up to the task of creating their own, right?

Maybe. But just because you can do something doesn't mean you should. The bar for developing custom apps for smartphones and tablets should be high, at least as high as it was for creating them on PCs. Here's a good rule of thumb: Web when you can; custom apps when you must.

It's easy to convince yourself to develop a custom app. Your organization may, for instance, support only iOS tablets and smartphones, so resorting to browsers and depending on HTML5 and JavaScript rather than native development tools seems unnecessary. Even if you envision supporting Windows 8 or Android mobile devices at some point, certainly the promise of "write once, run anywhere" development tools will solve that problem.

Unfortunately, none of the OS vendors is particularly interested in the success of WORA tools, so they'll make changes that will force both your chosen tool developer and your organization to make an update on the new platform. When Apple introduced iOS 5, it took months for even the commercial developer community to update all their apps. It's not as if the old apps broke--though some may have-- but if you're in for an ounce, you're in for a pound. Users will expect your app to work like all the rest. Apps on Apple devices can be a challenge, but Android significantly ups that challenge, as those releases are more regular and there's less guidance from Google on how the UI should look and feel.

[ Where does Windows fit into this picture? Check out our Windows Developer Roadmap. ]

The more frequent OS updates and differences in implementation from manufacturer to manufacturer have given WORA tools a less-than-stellar reputation. They're often dubbed "write once, debug everywhere." Whether or not they deserve that reputation, and whether or not they'll grow out of it, anyone looking to roll their own applications had better take the task seriously.

The short-term investment in creating those first pristine apps is likely to be the tip of the iceberg in terms of people and capital costs. Whether you're using internal teams for development or contracting with coding houses (a practice that brings its own set of challenges), you'll need to make a sober assessment of the short- and long-term costs of supporting the practice. Much in the same way that homeowners are shocked at the true cost and time to complete a home remodeling project, so it can be with software development. Estimates are made based on perfect conditions and often on an incomplete assessment of the business' lifetime needs for those apps.

Sometimes, the basic nature of the app you envision will require that it access resources that only a custom application can get at. If you need the app to access the device's accelerometer or near-field communications system, you'll probably need to write a custom app. As these features become standard in phones, you'll eventually be able to use them from Web applications. A bigger challenge comes around notifications. It's reasonable to envision pushing notifications to devices based on all sorts of things (inventory levels, orders shipping, hundreds of others). Web-based apps typically rely on email notification.

HTML5 and JavaScript aren't without their own challenges. Adherence to the HTML5 spec is by no means consistent everywhere, though you have a fighting chance across Apple and Android devices, as their Web browsers at least start from the same WebKit. But there's a lot to be said for creating one team that uses one set of technologies to field apps on everything from desktops to laptops to tablets to smartphones. For the vast majority of businesses, the mantra should be: Web when you can; apps when you must.

Art Wittmann is director of InformationWeek Reports, a portfolio of decision-support tools and research reports. You can write to him at awittmann@techweb.com.

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