As Web application platforms rise in importance and popularity, Google, Microsoft, MySpace and Facebook executives shared tips for keeping developers happy, disagreed on philosophical issues like standards and articulated wish lists of applications they'd like to see created.

The executives, who participated in the panel "The Platform Advantage" at the Web 2.0 Summit in San Francisco on Friday, generally agreed that platform providers must have concrete policies and rules for developers to follow.

Other best practices are to offer developers clear ways to generate revenue and to not treat them as rivals when they create applications that compete with those from the platform providers, the panelists said.

"From our standpoint, one of the most important things with our platform is that we have very clear guidelines, very clear rules, and we adhere to them," said Amit Kapur, MySpace's chief operating officer, referring to the company's recently launched application platform for its social-networking site.

Elliot Schrage, Facebook's vice president of communications, public policy and platform marketing, said his company prioritizes transparency in its dealings with developers, particularly regarding changes to the application platform. It's also important to seek and consider feedback provided by developers about the platform, and provide tools and resources, Schrage said.

In addition to clear ground rules and communication, platform providers must display a firm commitment to the platform, which in turn fosters confidence among developers that their investment of time, effort and resources is protected, said David Treadwell, corporate vice president of Microsoft's Live Platform Services.

"We want to make sure that the investments developers make are protected for the long term," Treadwell said.

A big no-no for platform providers is using their power to quash applications that compete with their own, the panelists agreed.

"If someone built a competitive application with our photo or mail products, we would welcome that. We want to see that because it's going to provide a better experience for our users," MySpace's Kapur said. "That keeps us relevant, keeps our users engaged with the core product, our social network."

Adopting an adversarial stance would damage beyond repair the trust of the affected developer, as well as that of the entire developer community, Kapur said.

Vic Gundotra, an engineering vice president at Google, seconded that view and extended it, arguing that control of the platform by a single provider by definition slows down innovation, a swipe at his former employer, Microsoft.

As an alternative he offered Google's approach with its platforms -- like the Open Social initiative for common social application APIs and the Android mobile operating system -- to open source all or portions of them.

To this, Treadwell defended the need for certain platforms to be controlled by a specific vendor, and challenged Google to release into the community the motor of its business: its search engine and ad platforms.

Gundotra retorted that he isn't advocating total community control, saying that a balance can be struck that also contemplates a vendor running a business on the Web platform. "The big story in the last 10 years has been Windows versus the Web, and the Web has won," he said.

At another point Gundotra took a contrarian view, telling his fellow panelists that the important thing isn't to extend any specific platform, but to focus efforts on improving the common Web that all of them use.

Facebook's Schrage cautioned that, while collaborating on ways to improve the underlying Web is certainly important, vendors should continue pushing ahead with advances in their own platforms and not slow down while questions about Web standards get worked out.

Asked what types of applications they would like to see developers create, the panelists mentioned various areas, including enterprise, health and mobile.