Dennis Crouch's patently-o blog (see link in side bar) reports that the U.S. Court of Appeals (Federal Circuit) has just handed down Phillips v AWH Corp. (Fed. Cir. 2005).
In this case, the court held that the primary source of reference for the meaning of words in a claim should be the specification rather than extrinsic references, such as dictionaries. The basis lies in the US statutory requirement that the inventor provide a "full" and "exact" description of the claimed invention. In spite of this, however, it is important to bear in mind that the court held that each patent still had to be treated individually. In other words, there may be cases where such a rule may not be appropriate. An interpretation must always be carried out in the shoes of a person of ordinary skill in the field of the patent. Such a person may find that the wording of the patent precludes limitation of the claims by a specification.
In Australia, Section 40 of our Act holds, inter alia, that a complete specification must describe the invention fully, including the best method known to the applicant of performing the invention. Proper claim interpretation requires that the description and the claims be read as a whole. This allows the description to set up a dictionary for the claims. However, our courts have held that the description must be read as a technical document, while the claims must be read as a legal document. Furthermore, if the claims are clear and unambiguous, the description should not be used to read meanings into the words of the claims. Only if the words are not readily understandable should reference be made to the description.
Given that many Australian-prepared patent specifications form the basis of US patent applications, practitioners should remain aware of developments such as these in the US.