According to T 517/98, if the disclosure of a patent in suit was limited to products which, when prepared by the method according to the invention, were characterised by distinctive parameters, then a claim which did not stipulate these parameters a priori encompasses embodiments which were not obtainable by the method disclosed. Such disclosure of a single way of performing the invention would only be considered sufficient if it enabled a person skilled in the art to carry out the invention within the whole ambit of the claim. In T 172/99, the board found that in the case of claimed subject-matter relying on a newly formulated and hence unfamiliar parameter to define the solution of a technical problem by which a relevant effect is achieved, the patentee is under a particular obligation to disclose all the information necessary reliably to define the new parameter not only (i) in a formally correct and complete manner such that its values can be obtained by a person skilled in the art without undue burden, but also (ii) in a manner which reliably retains the validity of the parameter for the solution of the technical problem for the application or patent in suit as a whole in the sense that the values routinely obtained will not be such that the claimed subject matter covers variants incapable of providing the relevant effect or, therefore, of solving the associated technical problem (followed in numerous decisions; see, for example, T 914/01, T 179/05 and T 75/09).
In T 815/07 the board pointed out that the purpose of a parameter contained in a claim is to define an essential technical feature of the invention. Its significance is that the presence of this technical feature contributes to the solution of the technical problem underlying the invention. The method specified for determining the parameter should therefore be such as to produce consistent values, so that the skilled person will know when he carries out the invention whether what he produces will solve the problem or not. This decision was cited in T 120/08 and T 593/09. According to the latter decision, what is decisive is whether the parameter is so ill-defined that the skilled person is not able, on the basis of the disclosure as a whole and using his common general knowledge, to identify (without undue burden) the technical measures (e.g. selection of suitable compounds) necessary to solve the problem underlying the patent at issue (see also II.C.7.2 " Article 83 EPC and clarity of claims" below).
The fact that no direct independent method of specifically determining the parameter has been described is not in itself prejudicial to the sufficiency of the description where the claims do not relate to a method of determining the parameter (T 256/87). In T 83/01 the board held that where the skilled person had no reason to doubt the definition of the parameter given, but there was no indication in the patent how to measure this parameter, the patent failed to fulfil the requirements of Art. 83 EPC 1973.
Where the calibration of (undisclosed) test conditions may be achieved even where the methods of determination of the parameter are incompletely described, the invention may be sufficiently disclosed. See for example T 1062/98. In both T 485/00 and T 225/93, three methods were known in the art for the determination of the specific surface area of a CaCO3 particle. In neither case did the description or common general knowledge indicate a preference for one of them. In T 485/00, the board held that reproducing an example and measuring the surface area of the resulting product by two or three well-known methods did not represent an undue burden for the skilled person. In T 225/93, however, the board found that, as there were three different measuring methods which did not always lead to the same result, this amounted to an undue burden. In T 641/07 the board held, citing T 485/00, that when a skilled person is enabled to reproduce the invention, and it is sufficient for him to reproduce one of the examples in order to identify the method employed to measure the value of a parameter, there is no insufficiency in the description since the identification procedure in question cannot be regarded as involving an undue burden.
Where it is obvious that a skilled person would select a particular analytical measuring method, (none being disclosed in the patent), balancing its simplicity and convenience against the required accuracy, the requirements of Art. 83 EPC are met (see e.g. T 492/92). This differed substantially from the case considered in decision T 466/05. In T 492/92 it was considered that the fact that two methods suggested by the appellant did not necessarily lead to identical results when measuring a specific parameter was not sufficient evidence that a skilled person could not determine this parameter of the claimed compositions with the required accuracy. In T 466/05, the skilled person did not even know which parameter should be determined and the invention was insufficiently disclosed.
See also 7.2 below.