Scientific information would be easier to find on the web if it were clearly marked as such. This is the promise of XML, soon to become the language of choice for web pages.

Current HTML coding tells browser programs little more than how a page should look. XML allows web pages to specify data and what they are, allowing browsers not just to read pages, but to process data referred to in the pages by machine readable tags, or ‘metadata’. Using XML, one could, for example, state that a page is a scientific paper, and provide information such as author, address and keywords. Tags can also represent fields in a database, allowing browsers to interface directly with datasets on the web.

“It would be possible to label a page as being about, say, the Viking missions to Mars, and have specific metadata attached to images that could identify them as being linked to the names of the features they depict,” says Robert Miner of Geometry Technologies, a company in St Paul, Minnesota, specializing in web sites for scientific applications.

Some experts are sceptical of any strategy that relies on the entire web community agreeing formats for tagging information. But in well-organized scientific circles, it should work better. Some disciplines have already drafted their own metadata standards, such as MathML, agreed by the mathematics working group of the World Wide Web Consortium (W3C). At present, mathematical notation is usually represented on web pages using image files, but with MathML it can be described precisely. This would allow researchers to search for pages containing particular symbols. Some software developers are already developing tools that will generate the metadata automatically.

The humble hypertext link is also set for a facelift. The W3C is developing XLink and XPointer, which will make hyperlinks much more sophisticated. Xlink will let users append their own links to pages on the web, for example, with a single link offering multiple destinations. Unlike today's hyperlinks, XPointer allows links to point to precise paragraphs or sentences, so search engines will be able to return the precise part of a document that seems relevant.