When I was a cub technology journalist, back in 1988, I met with Doug Michels, the founder of the network software company SCO. He pitched me on the insanity of the emerging market for stand-alone personal computers, especially in business settings. Like Scott "The network is the computer" McNealy, Michels believed that a well-connected, low-powered computer could do more than a poorly networked, high-powered PC--and for a lot less money.

Today, thanks to the emergence of Web-based applications using the new AJAX (Asynchronous JavaScript and XML) technologies, we're watching his vision come true, and not just in business. While it appears that the need for local stand-alone programs is in decline, I don't believe that Web apps will kill off local software completely. Furthermore, if you thought that running apps over the Web was going to reduce your dependence on high-powered hardware, think again. Let's look at a few different kinds of applications and see what's in store for PCs as more of these apps become available online.

1. Reference applications
The first mainstream local software category to be knocked off by online applications was that for reference CD-ROMs. In the mid '90s, with most users' available Internet bandwidth limited, it made sense for massive reference databases to be distributed on CD. But the Internet is clearly a superior medium for transmitting reference data: you can store more on the Net than on a disc, and the user gets the latest data.

Once people started adopting broadband, the need to distribute data on CD just died. But whether the reference application comes from a slot in the computer where you insert a disc or from a network port where you connect to the Internet, the reference application is still the same--and the need for processing power to run fancy graphics and multimedia applications is not decreasing. (By the way, we'll have a comparison of two DVD-based encyclopedias and the Web-based, group-think Wikipedia shortly. Stay tuned.)

2. Mapping
Mapping and route-finding are specialized reference services that require heavy computing resources to plot a trip and serious graphics horsepower to allow the user to manipulate the display. I've been a big fan of Microsoft Streets and Trips for many years, because it provided a much better user experience than the first-generation online mapping tools, such as Mapquest. But new tools, such as Google Maps (which uses AJAX), show us that browser-based mapping need not be locked into the old click-and-wait model of traditional Web applications: it's live, like Streets and Trips. The route-finding happens on Google's machines. And the user never has to worry about updating to the latest version, since Google's servers always provide the company's most up-to-date product.

Google also distributes the Google Earth application, a program you must install on your PC to use. There's still no application-free way to offer the deep user interface or the 3D graphics that this program offers. This highlights the difference between a local application (Google Earth) and a remote one (Google Maps). While remote apps are getting better, you can still do more with the user interface in local apps. And if you want to run 3D programs, such as Google Earth, you need serious local processing power.

3. Communications applications
The most interesting battleground in the Web-vs.-local fight is e-mail. Previously, Web-based e-mail paled in comparison to e-mail applications that ran locally. The user interfaces of Yahoo Mail, Hotmail, and even the vaunted Gmail just didn't compete with Outlook or any other locally run e-mail app. With local apps, you get a faster interface and more control over your messages.

A small company called OddPost changed all that, with a Web-based e-mail application that let you do nearly everything you could do with a local client, but running over the Web. OddPost was acquired by Yahoo and is becoming Yahoo Mail, and other Web-based e-mail services, such as Hotmail, are following suit with their own rich interfaces, all of which give the user the kind of speed and control over their e-mail environment that previously were available only in client software.

You don't need a high-powered PC to run a basic user interface. But even the fantastic Web-based e-mail clients we've seen recently need an active Web connection to operate. There is no local cache of messages in today's Web-based e-mail apps, which means that if you're on a laptop without an Internet connection or a local e-mail application, you can't work on your e-mail. Anybody who's ever devoted a few hours to catching up on e-mail during a flight knows that this makes Web e-mail no good as a sole solution for many users. People who need to work when they are disconnected--and that's most of us--need a PC with an e-mail application, a modicum of processing power, and local storage. For us, online e-mail applications--be they consumer e-mail like Yahoo or Microsoft's corporate solution, Outlook Web Access--are useful adjuncts to local e-mail applications. They are not a replacement.

For people whose computers are always connected, Web e-mail is becoming just as good as PC-based e-mail. And, of course, Web e-mail offers the bonus of being able to access your mail from any Net-connected machine.

4. Group database applications
The future of data-driven applications used by groups--things such as CRM, sales-force management, human resource applications, and accounting applications--lies on the Web. It's much easier to manage an application that is based primarily on shared data when the data, and the access to it, is run on a centralized machine or cluster of machines. Thus, we see the growth of companies such as Salesforce.com and increasing sales of the online-only verion of Intuit's QuickBooks.

Just as with e-mail, though, there are still advantages to local processing for group applications. Salesforce.com has a product for disconnected users, marketed as an adjunct to its main product, the Internet-hosted CRM application.

5. Productivity applications
Some intriguing Web-based office apps (such as ThinkFree) can do almost everything a local application does but with less speed, slightly fewer features, and at great risk that you'll be unable to work if you lose your connection. I don't know about you, but I don't want to run Microsoft Word over the Internet.

But many people do, or at least could, without much of a hit to their productivity. And for users with reliable Net connections who don't need all the bells and whistles of an installed office suite, an online version of traditionally local software can make sense, can be easier to manage, and can cost less. Google's recent alignment with Sun may ultimately be about just this: getting Sun's office suite, StarOffice, delivered to users over the Net, as they need it.

However, most of these online productivity applications shunt a lot of the functionality to the user's PC. And the more functionality you offer, the more local processing power you need.

So can you throw out your high-powered PC, hard drives, and operating system? Probably not. All of this incredible new functionality that's running over the Net won't fly on a TRS-80. Graphics- and user interface-intensive applications such as mapping and productivity need horsepower.

What is changing radically is how we buy software. More and more of it will be made available as a subscription, and ultimately, we'll probably not even know how much of any given application is running locally or what amount is running on a machine on the Net. Whether software serves us from our hard disk shouldn't be something we need to care about. But we're still going to need hardware to run our software, and the fancier our applications get, the more local processing power we'll need.

Are you ready to give up your local apps and run everything over the Web? Talk back!