Clearswift Ltd v Glasswall (IP) Ltd

In assessing obviousness, the court should use the structured Pozzoli approach, while keeping disclosure of the prior art distinct from the question whether the claimed differences were obvious. The first stages equip the court to answer the statutory question; they do not replace it. A patent claim directed to parsing each part of an incoming email, extracting and regenerating conforming content, blocking non-conforming content, and applying a sender-and-file-type threat filter was not obvious where the prior art disclosed only general filtering, rewriting or email recomposition. The skilled person may extend a prior-art teaching to commonplace email attachments, but a material gap remains inventive if bridging it would require more than routine development.

Clearswift sought revocation of Glasswall’s United Kingdom designation of European Patent EP 1 891 571 B1 under the Patents Act 1977. The challenge was confined to lack of inventive step in claim 1 over Cohen, a United States patent application, and Avecho, a series of Internet bulletin-board posts concerning Glasswall’s anti-malware software.

The court accepted that the skilled person was a computer science graduate with one to three years’ experience in the anti-malware software industry. The central issues were the proper construction of claim 1, what Cohen and Avecho disclosed, and whether the differences between those disclosures and the claimed parse-and-regenerate method, including its threat filter, were obvious.

1. Construction. Claim 1 required a full parse-and-regenerate process for each part of an incoming email. Conforming content was regenerated into a substitute file, while non-conforming content was blocked. The threat filter operated after parsing and before regeneration, and allowed non-conforming content through only on the basis of a stored combination of file type and sender. The court rejected the wider construction advanced by Clearswift.
2. Applicable approach. The court adopted the four-stage structured approach in Pozzoli: identify the skilled person and common general knowledge; identify the inventive concept or construe the claim; identify the differences from the prior art; and ask whether those differences were obvious without knowledge of the invention. The first three stages were tools for answering the statutory question and could not be treated as a substitute for it. Disclosure and obviousness were distinct inquiries.
3. Cohen. Cohen disclosed dissecting and recomposing email messages, with correction or omission of components. It did not clearly and unmistakably disclose parsing attachments to content level, regenerating components, a substitute regenerated file, or the claimed sender-and-file-type threat filter applied after unsuccessful parsing and regeneration. Extending Cohen to attachments and determining their file types would have been obvious, but the missing parse-and-regenerate process and the particular threat-filter operation were substantial differences. Bridging those differences would have required invention.
4. Avecho. Avecho disclosed filtering, alteration or rewriting of emails, recognition of different file types, and processing according to those types. It did not clearly disclose parsing each part according to its specification, extracting content, regenerating the parts, or the detailed threat filter required by the claim. The additional disclosures were not obvious over Avecho.
5. Disposition. Claim 1 was not obvious over either item of prior art. Clearswift’s application for revocation was dismissed.

First-instance decision. No earlier appellate decision is stated in the judgment.