Making various Web languages work together, bringing Web functions to mobile computing devices and making the Web's benefits available to people in rural areas and developing countries are among the tasks developers are still facing, said Berners-Lee.
Berners-Lee kicked off his speech by announcing the formal approval of the Extensible Markup Language (XML) Schema as a W3C recommendation, the final sign-off for a W3C standard. XML Schema defines how programmers should describe content using XML, which can put an identifying tag on any piece of content on the Web.
Now, "there's an XML language for defining XML languages," said Berners-Lee.
He also pointed to new technologies now becoming viable as signs of progress: Extensible Hypertext Markup Language (XHTML); Scalable Vector Graphics (SVG), which Berners-Lee used to zoom in on charts in his presentation; Cascading Style Sheets (CSS) for XML; and Mathematical Markup Language (MathML) for giving mathematical notation on the Web.
However, making all these specifications and others work together will take more work, he cautioned. Developing new kinds of interfaces, such as a voice interface for drivers, and making computers talk to each other for automated Web services also are key tasks, said Berners-Lee.
Another concern that will come to the fore as electronic commerce grows will be the persistence of critical kinds of communication, such as the electronic equivalent of a cheque written for a product or service, he said.
Consumers and businesses may keep canceled cheques as proof of payment, but "you don't keep your IP [Internet Protocol] packets," Berners-Lee said. Documents on the Web should be able to identify themselves so they can be examined later, after the Web formats in use have changed.
Another key technology now being polished by the W3C is Resource Description Framework (RDF), which provides interoperability among applications that exchange information from one machine to another on the Web. It can use XML to exchange descriptions of any Web resources, including non-XML resources.
A diagram showing dozens of interconnected circles and squares - including things the W3C wants the Web to achieve and the protocols and software elements it will require - demonstrated the hard work ahead.
"It's difficult when there are so many blobs," said Berners-Lee.
Attendees of the conference applauded the approval of the XML Schema, which is intended to replace the many Document Type Definitions that have been used to describe the contents of different kinds of Web documents.
"The XML Schema is just more powerful. It allows you to be more expressive in the way you describe your documents," said Stefan Edlund, a software designer at IBM's Almaden Research Centre, in California. The technology will be important for business-to-business commerce, Edlund said.
The XML Schema will help to rein in ways of defining Web content, making the definitions more consistent, said Amit Singal, a senior research scientist at Google, the US-based Web search company. "It's going to make all kinds of data interchange possible that's not possible today," said Singal.
A companion of Singal's, however, cautioned that today's approval is only one step.
"It's a milestone, yes, but it's still going to have a lot of flux," said Soumen Chakrabarti, an assistant professor in the computer science and engineering department at the Indian Institute of Technology, in Mumbai.
The World Wide Web Conference continues until 6 May.
Visit the W3C at www.w3.org