The crucial role of the seemingly harmless expression "data transmission delay" in the decision T0480/12 reminds me of this monster pawn of Viswanathan Anand. In the end, these words turned out to be as fatal as was the pawn for Magnus Carlsen:
Here is a quote from the grounds of opposition (emphasis added):
The feature "data transmission delay or latency" was introduced to replace "delay of data" during the examination procedure at which the latter had been regarded as unclear, because of leaving the reader in doubt as to the kind of processing referred to, e.g. processing delay, queuing delay or transmission delay (see communication of 4 November 2004, point 1.3). In the course of the opposition procedure the term "or latency" was deleted in the aim to overcome an objection as to added subject-matter. The respondent objected to the remaining feature "data transmission delay" for lack of clarity and argued that the term was no longer clear due to the deletion of "or latency".
Moreover, the interpretation of the term "data transmission delay" on the basis of the description, see in particular paragraphs ,  and  was different from how this term was used by the skilled person.
While the appellant pointed out that the expression "data transmission delay" was clear in the light of the description of the patent by referring to paragraphs ,  and , the board agrees with the respondent that a claim has to be clear per se (see T 1129/97 dated 23 June 1998, point 2.1.2). However, when referring to "data transmission delay" in claims 1 and 7, in particular since the words "or latency" were removed from "data transmission delay", the skilled person would have an understanding of the expression different from the description. As is apparent from e.g. prior art documentThis means that:
A8: Rosado, Sosa C et al: Jitter compensation scheduling schemes for the support of real-time communications ,ICC 98, Conference Record, 1998 IEEE International Conference On Atlanta, GA, USA 7-11 June 1998, NEW YORK, NY, USA, IEEE, US, 7 June 1998, pages 885-890,
referred to by the respondent during oral proceedings, there are different types of delay like propagation delay, processing delay, queuing delay, transmission delay etc. (see e.g. section 2.1). Without further specification, the skilled person would interpret the expression "data transmission delay" in claim 1 to refer to this special type of delay rather than to the whole delay. The skilled person would not understand claim 1 in a way that it is referred to more than the transmission of the data without further considering the description.
- words used in the claims must have a clear meaning per se;
- the claim is unclear in cases where this meaning is modified when reading the claim in the context of the specification (which is always true to some degree...).