A Better Way to Share Information

XML schema permits rich data descriptions; W3C standard promises to streamline exchanges.

XML schema, released last week as a World Wide Web Consortium recommendation, is the most important new standard from the W3C since XML itself, making it much simpler for applications, data repositories and business partners to exchange and integrate data based on Extensible Markup Language.

Tim Berners-Lee, creator of the Web and director of the W3C, announced the release during his keynote speech here at the Tenth International World Wide Web Conference.

XML Schema, which has its roots in XML Data and SOX (Schema for Object-oriented XML), was introduced in early 1999. XML Schema is designed to make it easier to exchange XML data models and integrate disparate XML data. This is difficult to do with XML, which uses Document Type Definitions.

With XML Schemas XSD (XML Schema Definition), rich data descriptions are now possible. The standard defines a set of shared markup vocabularies, thus providing a method for describing data in an XML file.

The ability to build schemas to a standard should increase the effectiveness of business exchanges and the new Web services strategies on which several large software vendors are working.

Despite all of these potential benefits, there has been disagreement from high-profile members of the XML community, as eWeek reported last month. XML Schema has been criticized for being too large and too complex.

However, XML Schema is as big as it needs to be, according to David Fallside, author of the XML Schema primer and member of the XML Schema working group in Santa Clara, Calif. "The size of XML Schema simply reflects the job that schema set out to do," Fallside said.

Michael Rys, program manager for SQL Server XML Technologies at Microsoft Corp., in Redmond, Wash., concurred. "XSD is, of course, more complex, but thats because it allows you to do a lot more," Rys said.

It took more than two years for the schema to become a standard. In the meantime, many businesses have turned to alternative schema technologies for data exchanges and products. Many of these developers will need to start the move to the XML Schema standard.

"I think that it will be relatively easy to move from other schemas to XSD," Fallside said, adding that this would be especially true for schema such as SOX and XDR (XML Data Reduced).

Because most of Microsofts XML technologies are based on XDR, the company has some experience porting to XSD (its BizTalk Server includes a tool for converting from XDR to XSD); Rys said that in most cases it will be easy to move to XSD from XDR, which he said is practically a subset of XSD.

"You dont need to use all of the complexity for every implementation," Rys said. He also said vendors will probably write applications that shield users from many of the complexities.