About a year ago, Payet Guillermo's systems and Web development work called for more robust capabilities for the sharing of information and applications. That's when he started dabbling in XML.

XML is an important skill to master, because more clients are asking to link data sources and applications for use on Web sites and for back-office integration. And they'll soon be asking for business-to-business extranets as well, says Guillermo, president and chief technology officer at Ocean Group in Santa Cruz, Calif. "XML is already here, and it will eventually be very widely used," he notes.

The slowing technology market has taken a toll on Guillermo's IT consulting business he had to lay off nearly his entire staff of 20. But he's staying busy with XML work for Web businesses that want to push paid-for content to their sites.

One of his clients, a women's sports clothing Web site, wanted a front-page window running scores of women's sporting events. London-based Reuters Media's news service provides the scores in XML format. Guillermo's job was to parse that data and translate it back into the client's native Java environment. After much research, he chose The Apache Software Foundation's Xerces XML parser, which is also available for C++ translation.

Applications like these often relay data directly between application servers housed at different companies. This makes security knowledge an important part of the job, Guillermo says. For example, he's now working with a company that wants its Web visitors to be able to query a back-end database for astrology information.

That astrology data actually comes from a third-party news service. Packaged in XML, the data is transferred to an application server at the Web business, where it's then pulled up to the user in HTML.

"We're putting an XML wrapper around code someone else has already written, and then the Web business can format it anyway they want," Guillermo says. "So you really have to pay attention to securing the data transport in these one-to-one connections, especially authentication."

This is where inquisitiveness becomes key. Working in XML during this early stage means following the many standards coming from the World Wide Web Consortium (W3C) and vertical industries, Guillermo says. While the W3C's authentication and public-key infrastructure standards make a good starting point, XML developers must also track down best development practices, vendor developments and the evolution of standards.

"There are so many standards. And those standards are so immature," Guillermo says with a sigh.

The actual process of wrapping data in XML tags to identify that data is easier than doing so in HTML, because XML provides a set syntax, Guillermo explains. You also need coding languages such as C and Java to convert objects into XML, send them to another connection and parse them back into objects again.

"There are very few XML-specific jobs, just as there are very few SQL-only jobs," Guillermo says. "But the XML skill set will be essential for systems developers, particularly if they're working in systems integration in business-to-business."

Structured-documents specialist is another title arising out of the data-linking, -wrapping and -translation work in XML and its variants, says Dan Moniz, research scientist at peer-to-peer IT services company OpenCola Ltd. in Toronto. "Structured-documents specialists will need to understand the semantics and come up with schemas for information, metadata and tag sets. It is essentially information organization."