If an essential feature of the invention is expressed by a parametric definition, the question is whether the parameter is so defined that the person of the art, on the basis of the disclosure of the patent as a whole and using his common general knowledge, could identify, without undue burden, the technical measures leading to the claimed subject-matter (T 61/14).

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 in this chapter II.C.8.2. " Article 83 EPC and clarity of claims").

In T 147/12, the objection of the appellant (opponent) was not that no method of determination of the alkali metal content in polyethers existed. Rather, the gist of its argumentation was that D7 (scientific publication), D8 (a study) and D11 (experimental report provided by the opponent) showed that the value obtained for the alkali metal content in the polyether depended on the analytical method used for its determination. The board stated that even if the conditions of measurement lead to variations of the value of the alkali metal content as argued by the appellant, this alone did not constitute a lack of sufficiency of disclosure regarding the claimed subject-matter as a whole since it had not been shown that the uncertainty concerning the alkali metal content affected the claimed process to such an extent that the skilled person wishing to perform the process would face an undue burden. The appellant had shown that the uncertainty concerning the method of determination of the alkali metal content meant that the skilled person could not ascertain whether the value he would obtain was within or outside the claimed range. It was, however, not shown that as a result of that uncertainty, the skilled person would fundamentally be prevented from obtaining a polyether according to claim 1. The board stated that T 83/01 (skilled person not in a position to perform any measurement of the claimed parameter) and T 815/07 (test method defined in claim 1 resulting in totally arbitrary values) were not applicable to the present case.

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, case concerning Art. 84 and 83 EPC, compliance of amended claim 1). 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. In T 808/09 (cartridge for use in a beverage preparation machine / liquid chocolate ingredient), the board considered that the patent failed to enable the measurement of the essential parameter of the invention, i.e. the viscosity of the liquid chocolate ingredient. Even if this viscosity feature had been shifted into a preamble of method claim 1 and supposing this preamble had been directed to the prior art, this shifting of the feature would still not have solved the problem of insufficiency. For a reference to prior art in the preamble to adequately serve this purpose the patent in suit still needs to contain all the necessary information in sufficient detail in order to enable the person skilled in the art to perform the invention. In the case before the board this would require information as to the viscosity measurement device to be used and the parameters to be observed. All this information was missing. The board's decision, taken in line with the long-standing jurisprudence, cited T 805/93 (dealing with viscosity measurement at "room temperature"), T 83/01 and T 1250/01 (both concerning the measurement of an essential parameter).

In T 2096/12 the skilled person could not know, from the disclosure in the patent, which measurement method should be employed to establish the claimed thickness parameter. The board agreed with the statements in T 593/09 and emphasised that the absence of a test method for a parameter which was a claimed feature did not lead by itself to the issue of insufficient disclosure. In a case where, for example, ranges for length or width of a clearly structured article were concerned, the parameters could be established unambiguously and without doubt. However, in each case it had to be evaluated on a case by case basis whether this was possible. When the extent of the protection conferred by the patent is not defined and cannot be reliably determined – such as in the case at issue where neither the claims nor the description provided a clue for how to interpret the parametrical feature of the claim, it can only be concluded that the requirement of Art. 100(b) EPC was not met.

In T 1064/15 the person skilled in the art was faced with the undefined parameter "diameter (SD)" and did not know how to choose the cross-section in order to obtain the desired technical effect. For the conditions of sufficiency of disclosure to be fulfilled it is not enough to be able to manufacture an object falling under the wording of a claim. That object must also exhibit the alleged or desired technical effect obtained with that invention (T 815/07). The field of non-circular cross-sections is far wider than that of circular ones, since it encompasses an enormous variety of shapes. This made it even more important to know how the key parameter of such shapes, namely the diameter, was determined.

The board in T 602/10 found that the proprietor had deliberately decided to use a method for determining rugosity which was different from the one commonly used in the state of the art. It was therefore its duty to provide full information with regard to the means and the procedures for implementing said method. In general terms, when the issue of sufficiency concerned the description of a method for determining a parameter, the less common the method the more accurate the information provided in the description should be. In the case at issue, in the absence of any known prior-art work applying the same method used in the patent for measuring the rugosity, the skilled person had to rely primarily on the teaching of the patent to put the method into practice.

Where the calibration of (undisclosed) test conditions may be achieved although 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 417/13, the board stated that in the case underlying decision T 225/93 the prior art contained no indication of which method of measurement was suitable in particular for the calcium carbonate particles under consideration. Unlike the situation in T 225/93, in the present case it was determined that one particular method of measurement would have been chosen by the skilled person. Then the board in T 417/13 concluded that in the present case of PVC particles the skilled person would not have considered using any method of measurement, but would have chosen a method relying on sieving, such as a method according to ISO standard 1624. There was no evidence on file that different measurement conditions in such a method would have led to the selection of PVC particles that would have prevented the skilled person from carrying out the invention as defined in the claims.

In T 641/07 the board held, citing T 485/00, that when a skilled person was enabled to reproduce the invention, and it was sufficient for him to reproduce one of the examples in order to identify the method employed to measure the value of a parameter, there was no insufficiency in the description since the identification procedure in question could not be regarded as involving an undue burden. In T 1712/09, the board held that the opponent had failed to prove that the method of measuring the parameters was unworkable. The tests referred to in its experimental reports had been carried out using measuring apparatus different from that described in the patent, and so not as instructed there. The board found that no attempt had been made to reproduce the invention (no attempt at calibration), which was the first condition for an objection under Art. 100(b) and 83 EPC. It cited T 815/07 (need for consistent values) and T 1062/98 and T 485/00 (possibility of calibrating methods of determining the relevant parameters). The board in T 548/13 held that the case law on parameters (which included T 815/07) did not apply since the case before it did not concern a quantitative parameter.

In T 45/09 too, the opponent's test conditions were called into question since the tests had been carried out using a commercially available product. Observing that two products of the same brand but available on the market at different times would not necessarily have the same properties, the board found that it had not been established that the properties had been the same in this specific case. The board also considered the issue of calibrating the method of measuring the parameter. The board concluded that the opponent had failed to show that the method of measuring the parameter could not be reproduced and thus to prove insufficient disclosure. It was, indeed, for the opponent to do so, and it could have discharged its burden of proof by attempting to reproduce the method using at least one of the claimed silica.

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.

The board in T 2403/11 acknowledged that an ambiguity of a parameter in the claim was not enough in itself to deny sufficiency of disclosure. Whether such an ambiguity led to insufficiency of disclosure was to be decided on a case-by-case basis (see T 593/09 and T 472/14). The case at issue was different from T 882/03, which also concerned viscosity and where the variations resulting from the ambiguity were only minor, and from T 492/92, where the skilled person knew which method to choose. In T 2403/11 the method and the measurement parameters to be chosen were not known to the skilled person. T 482/09 also concerned a method of measuring viscosity (see also T 808/09 and T 805/93 supra). In T 1697/12 the claims covered, through open-ended ranges, embodiments that could not be obtained with the process disclosed in the patent, but which might be obtainable with different methods still to be invented in the future (insufficiently disclosed invention).

Where inventions are defined by claims containing unclear features, e.g. ambiguous parameters, which cannot be clarified in the light of the description, the effect sought may be the only means of understanding such inventions. This effect must then be taken into consideration and assessed under Art. 83 EPC with a view to establishing whether the invention can be reproduced (see T 862/11).

See the very recent decision T 1845/14 (ambiguous parameter; see catchword – this decision addressed several issues).

See also in this chapter II.C.8.2.