Sun Microsystems president Ed Zander has launched a wide-ranging attack on Microsoft, including an accusation that the Redmond giant will backtrack on its recent commitment to open internet standards.

Speaking to journalists in London yesterday, Zander compared what he describes as Sun's open approach to XML (eXtensible Markup Language) development with the course he claims Microsoft is charting.

"With Microsoft and XML you can expect to see them burying it and changing the APIs [application program interfaces], and making it only work with their software," said Zander.

He said his opinion is based on a comparison of Microsoft's approach towards XML with its development of ActiveX and component protocols such as DCOM (Distributed Component Object Model), which are proprietary.

Mitul Mehta, managing director of independent consultancy TekPlus, said the market is looking for open solutions and, at this time, no company is powerful enough to produce XML tools that do not offer interoperability.

"XML is still being developed and I expect most companies to play by the book until at least the second or third versions of their products, so that basic APIs will work with those of other vendors," said Mehta.

Relations between Sun and Microsoft, which have never been cordial, have been strained further by last week's announcement that the European Commission has started a formal investigation of Microsoft's practices in the server software market, acting on a complaint by Sun.

The Commission is investigating whether Microsoft breached European Union antitrust rules by engaging in discriminatory licensing and refusing to supply essential information on its Windows operating system to server vendors.

Microsoft said Sun is trying to gain by a legal process what it has failed to achieve in the marketplace.

In a statement on the Commission's case, Microsoft said: "We are disappointed by Sun's attempts to use government intervention to overcome the fact that Microsoft products are outperforming theirs in the marketplace and for one third of the cost."

Zander reacted angrily to the statement. "Microsoft's response shows a lack of respect for the laws of our world. Nobody likes to go to court, but the reason courts are there is to enforce laws," he said.

Turning to Sun's business, Zander said the vendor, which has recently released a network attached storage appliance, is considering the introduction of caching, firewall security and directory appliances.

"The appliance model, with an integrated stack, is a promising way of delivering continuous uptime. Sun has never worked with single function devices before, but now this might work because of the power of the network," he said.