Long-range plans for improving the Java programming language are taking shape at Sun Microsystems, with XML a focus at this early stage.

Even with the planned "Mustang" release of Java a year away, Sun already is pondering what to put in a subsequent release, code-named "Dolphin" and planned for delivery in the second half of 2007. This release officially would be known as J2SE 7.0 whereas Mustang would be J2SE 6.0.

A key feature being considered for Dolphin is native XML data support.

"There"s been some thought given to the notion that maybe we don"t have quite the right model for XML" at present, said Mark Reinhold, chief engineer for J2SE at Sun.

Sun is pondering high-level APIs for manipulating XML. Developers would be able to write XML text into code and be able to manipulate it without having to write method invocations, Reinhold said. Method invocations can lead to very verbose code, he said.

XML boosts and language features in general are not planned for Mustang, which is set to focus on Web services, the Java desktop, and large-systems performance. "We did a big batch of language features in Tiger [also known as J2SE 5.0], and some tools vendors are still catching up with those," Reinhold said. J2SE 5.0 shipped in September 2004 and has had 15 million downloads, according to Reinhold.

There also is talk about adding byte codes in the JVM within Dolphin to make scripting languages such as Groovy run faster, Reinhold said. But it is not known if the proposed Multi-Tasking Virtual Machine, which is the subject of a research project, would turn up in Dolphin. The project is still in a prototype stage, Reinhold said. The Multi-Tasking Virtual Machine would address issues with memory footprint, startup, and execution times when running Java applications concurrently.

In talking about Dolphin, Reinhold stressed that the release is still in the early planning stages. "We"re still in the middle of finishing details of what"s going to be in Mustang," Reinhold said. Improvements planned for Java by Sun would have to be submitted for consideration by the Java community at large via the Java Community Process.

Talk about Dolphin at this point is "wild conjecture," said Rick Ross, founder of Javalobby.org, an online community for Java developers.

"I am certain that there are many real-world developers who would accept a moratorium on new feature development if the resources could be channeled to long-standing bug fixes," Ross said. "Reliability and performance are at least as important, in my opinion, as new features."

But Reinhold said he believes Java quality has been improving markedly.

"There"s always a delicate balance to be made between fixing bugs and providing new features. We at Sun think we"ve done a pretty good job over the years of managing that balance," Reinhold said. "It"s a very hard game in which to try to make everybody happy."

Following the Mustang and Dolphin releases, enterprise-level versions of these technologies would be expected. Sun may discuss future Java technologies at its JavaOne conference in San Francisco, held the last week of June.