In the decision Scheinwerferbelüftungssystem (X ZR 16/17), the German Federal Court of Justice was concerned with the issue of claim interpretation in terms of prior art described in the patent. As a general principle, highlighted in the decision, it must be considered for claim interpretation that a patent with its teaching seeks to delimit itself from prior art described therein. In particular, if the content of a state of the art description is equated with the preamble of a patent claim, the features of the characterising portion must, in case of doubt, not be construed as being part of the subject matter of the state of the art from which they shall differ.
