While the landscape for rich Web development technologies is getting crowded, industry dignitaries at The Rich Web Experience conference in San Jose, Calif. Thursday nonetheless saw a place for the various entrants in this space.

The field of technologies has grown to include AJAX (Asynchronous JavaScript), Adobe Flex, Microsoft Silverlight, and Sun's JavaFX, said Neal Ford, application architect for Thoughtworks, who moderated a panel addressing rich Web development. Audience members also gave a nod to the Ruby, Python, and Groovy languages.

Panelist Scott Davis, an author and consultant, said he originally thought that AJAX would rule the world. "It runs in any browser," Davis said. But his horizons have expanded.

"Quite honestly, I've gotten really interested in Flex recently," Davis said. The recent open-sourcing of Flex has made it more attractive, he stressed.

AJAX drew affirmations with reservations from panelist Jon Ferraiolo, an IBM Web architect who manages the OpenAjax Alliance. "My perspective is that AJAX works today. It's fantastic, it does nearly everything you want to do except for multimedia types of things," Ferraiolo said.

"I think there's room for Flash, Flex; there's room for Silverlight. These things are going to be the cutting-edge applications that require the latest features," said Ferraiolo.

With the proliferation of mobile devices however, HTML browsing will not be available on all these systems, and the iPhone does not have Flash and probably will not have Silverlight either, said Ferraiolo. AJAX, however, is always there and is open and can be counted on, he said.

"There is a continuum of experience that needs to be looked at," said Josh Holmes, an evangelist at Microsoft who is speaking on Silverlight at the conference. There is the standards-based Web with HTML and CSS (Cascading Style Sheets) and there is AJAX, he said. Moving on, there are platforms optimized for a particular OS or hardware that can render 3D graphics, said Holmes.

"My personal opinion is that Silverlight and Flex are definitely on that heavy, rich but not quite platform-optimized edge," Holmes said. There are benefits to both, he said.

Another panelist sided with Flex for enterprise usage. "In the enterprise space, I tend to recommend things like Flex because the development is much faster to get up and going," said Bill Scott, AJAX evangelist at Yahoo.

"Creating a desktop style [application] in AJAX is still really hard," Scott said. AJAX does fit into a lot of areas, but none of the rich Web technologies will rule the world, he said.

Panelists also addressed the question of application-testing.

"Yes, testing is absolutely crucial, and as an industry, it's something we have not taken seriously for the last couple of years," Davis said.

"I think this is a space that the market realizes isn't served really well right now," said Ryan Breen, vice president of technology at Web performance tester Gomez.

The Crosscheck open-source testing platform was cited by panelist Stuart Holloway, co-founder of software developer Relevance.

The issue of tools for JavaScript was raised. IntellliJ, said Davis, "has got killer JavaScript support, and it's got wonderful CSS support," he said. But lately, he has been developing with the simpler TextMate tool.

"I've found that the overhead of a big heavy tool is less valuable to me than having something that's easy for me to bring up, bring down, refresh," Davis said. This lighter format seems to fit the Web development model, he said.

Panelists and an audience member also mourned the lack of staying power of SVG (Scalable Vector Graphics).

"SVG just breaks my heart," Davis said. "SVG had the opportunity to be kind of a unified solution. I wish it would come back strong, but I'm not holding out hope."

Silverlight, Holmes said, uses XAML instead of SVG. "My opinion is SVG has kind of stalled and there were some things that were needed beyond it," so Silverlight uses other technologies instead, Holmes said.

Ferraiolo said he was one of the initiators of SVG while at Adobe. "SVG was there in 2001, 2002, but Adobe decided to pull the plug on it despite the fact that it was on 200 million desktops," he said.