Ray Ozzie introduces Windows Azure at Microsoft's Professional Developers Conference in Los Angeles Monday.

LOS ANGELES — The Ray Ozzie Era at Microsoft has begun.

The man who assumed Bill Gates’ role of chief software architect unveiled a new blueprint for the company here this week, detailing plans to build upon Microsoft’s PC software legacy in an attempt to ensure the company’s place in the online world.

Just as Gates led Microsoft through the personal-computer revolution, Ozzie is trying to lead the company into a new period of “cloud computing” — in which programs are accessed on computers and devices as online services from remote data centers.

“The data center, in some senses, is the kind of technology platform that Microsoft hopes it can eventually take over the way it took over PCs,” said analyst Rob Helm, director of research at the independent Directions on Microsoft research firm in Kirkland.

But the Redmond company faces stiff competition from the likes of Google, Salesforce.com and Seattle-based Amazon.com, all of which have beaten Microsoft to market with cloud-based offerings of their own. And even if Microsoft does succeed in reshaping its business in the long run, it could see thinner profit margins if its product mix shifts away from its lucrative lines of traditional software for PCs and computer servers toward potentially less costly online versions.

However, Ozzie said in an interview that he doesn’t believe online services will elbow out PC-based software. Rather, he said, the company envisions services supplementing software and, in many cases, adding to its business. Whereas other companies tout the move toward “software as a service,” Microsoft prefers a different phrase.

“I know that people don’t like the term, but I would say ‘software plus services’ defines Microsoft’s future more than just cloud computing itself,” Ozzie said.

The core of the company’s new initiative is the “Windows Azure” cloud-computing system, announced at the Professional Developers Conference in Los Angeles this week. Through Azure, Microsoft will sell software developers access to its worldwide network of data centers, enabling them to use Microsoft’s infrastructure and tools to build and deliver online services for end-users.

Microsoft is making the expansion to cloud computing at a tumultuous moment for its biggest software business. The company this week unveiled a preliminary version of Windows 7, its next update to the PC operating system -- slated for release in 2010 -- and conceded that it made a series of missteps in its development of the current version, Windows Vista.

The cloud computing initiative is a positive move for the company, but in a broader sense, it doesn’t appear to be enough to offset concerns about the traditional Windows business, said Donovan Gow, an analyst at American Technology Research. Those concerns include the possibility of low-cost laptops diminishing Microsoft’s average Windows selling price and new headway being made by Apple in the consumer market.

One lesson Microsoft learned from Windows Vista was the importance of working closely with industry partners to make sure everything works together smoothly, Ozzie said. He explained that the lesson will apply to the cloud computing initiative, as well.

Microsoft is making one of its first big moves toward cloud computing with its venerable Office franchise. The company this week announced plans to offer scaled-down versions of its widely used Office programs as online services over the internet — letting people compose a Word document inside a web browser, for example.

It’s not a revolutionary concept. Google and other companies have long offered the ability to compose, edit and share word-processing files and spreadsheets inside a browser. But Microsoft has been slow to offer online alternatives to its lucrative Office programs. The Microsoft Business Division posted more than $12 billion in operating profits last fiscal year, largely from sales of Office software and related products.

The company hasn’t said how much it will charge for the web-based versions of Word, Excel and other Office programs. So the potential impact on Microsoft’s bottom line isn’t clear. But in general, Ozzie said, Microsoft believes cloud-based applications will add to its revenue, rather than cannibalizing its traditional software businesses.

Based on its research, Microsoft believes that people will use web-based Office programs primarily for drafting short documents and collaborating. Ozzie said he believes people will still use standard PC-based programs for composing big documents. Unveiling Azure this week, Ozzie credited Amazon.com for leading the way with its existing cloud-computing platform.

At the same time, Microsoft says it will offer a more complete system for developers. Microsoft hasn’t disclosed pricing for Windows Azure either, but Ozzie said in an interview that competition in that part of the market limits the amount the company can charge.

“The margins will be thinner,” Ozzie said. “There will be multiple providers. We’re going to be a great provider, but I’m sure there will be other providers.”

Those thinner margins could hurt Microsoft’s overall business if cloud computing causes companies to make a big shift away from traditional computer servers. Microsoft’s Server & Tools Business — which sells operating systems, database software and other programs for those servers — has been a financial mainstay for the company.

However, Ozzie still sees a big role for those traditional servers inside most companies, even as many applications move online. “People will still run most of their big business systems — the back ends of their big business systems — on premises,” he said.

Ozzie, a software pioneer known for creating Lotus Notes, joined Microsoft in 2005. Along with Craig Mundie, who oversees the company’s long-term technological vision, he is one of two executives filling Gates’ role following the Microsoft chairman’s departure from day-to-day duties this summer.