BT suffered a setback in its patent-infringement lawsuit in the US against ISP Prodigy last week when an initial ruling narrowed how BT can present and defend its claim to have invented hyperlink technology.

Judge Colleen McMahon of the New York Federal Court issued a 38-page opinion in the pretrial discovery phase of the case, weeding out some of BT's terminology and phrasing supporting its claim, according to court documents.

The judge ruled on the disputed definitions in the patent, the so-called Markham phase of the process. The next stage is to debate the claims for originality that the patent makes.

BT declined to comment on the case and representatives at Texas-based Prodigy could not be reached for comment.

BT contends its Hidden Page patent, filed in the US in 1976 and granted in 1989, gives the company the intellectual property rights to the hyperlink technology.

Hyperlinks connect text, images and other data on the internet in such a way as to allow a user to click on a highlighted object on a web page in order to bring up an associated item contained elsewhere on the web.

On 13 December 2000 BT filed suit in federal court in New York state to protect the patent which it contends covers the invention of the hyperlink technology used in web pages.

According to BT, the technology for its hyperlink patent originated from general research done on text-based information systems, including a system called Prestel, by an employee of the General Post Office in the 1970s. The GPO was split into BT and the Post Office in 1981.

BT contends that, though Prestel is at best a primitive online information system, the system can still prove its claims of prior art.