Williamson et al. v. IBM

This case involves classic issues of claim construction. In construing claims, courts look first to the words of the claims themselves.  They will also look at the specification, the prosecution history, and, lastly in terms of priority, relevant extrinsic evidence.  One of the rubrics of claim construction is that the specification cannot be used to limit the claims except to the extent the specification informs the interpretation of ambivalent language the claims contain.

Patent drafters nevertheless remain concerned that limitations from the specification will be read into the claims. This has led to various policies such as never using the word “invention” and never using the word “preferred.”  In this case, however, the use of the word “preferred” consistently before every instance of a particular limitation was used to reject the district court’s conclusion that limitation was inherent in the term to which that preference applied.  It helped that the specification contains an explicit and sufficient definition for the disputed language.

My personal opinion is that drafters should be decisive regarding the interpretation they want for the claim language they choose and use the specification to eliminate ambiguities. There is some thinking out there that one can leave ambivalence in the claims and specification and that a litigator will sort it out when the patent is enforced.  I disagree with that thinking.  My sense is that ambiguity is more likely to hurt than help the patentee.

This case also notes that a term commonly used by persons of skill in the pertinent art to designate structure provides a valid structural claim limitation even if the term covers a broad class of structures and identifies the structures by their function. In particular, the word “module” in the phrase “distributed learning control module” was found (by the majority – there was dissent among the judges) to be a structural limitation having a well understood meaning to those skilled in the computer arts.  The rule is not new with this case, but it is important to note.  There seems to be a trend among patent examiners to interpret functionally defined structural limitations as mere statements of intended use having no patentable weight.  The lesson is that terms of art are often a good source for claim language that is widely inclusive while remaining effective for defining the scope of a claim.