The same level of skill has to be applied when, for the same invention, the two questions of sufficient disclosure and inventive step are being considered (T 60/89, OJ 1992, 268; T 694/92, T 187/93, T 412/93). However, the standard of disclosure required for amendments by Art. 123(2) EPC 1973, namely that of being directly and unambiguously derivable, is inappropriate, the criterion being that it must be possible to reproduce the invention on the basis of the original application documents without any inventive effort and undue burden (T 629/05; cited in T 79/08).

It is the same skilled person that has to be considered when construing the subject-matter of a claim. It accordingly follows that the construction of a particular claim should be identical for the assessment of inventive step and sufficiency of disclosure (T 967/09).

The skilled person may use his common general knowledge to supplement the information contained in the application (T 206/83, OJ 1987, 5; T 32/85, T 51/87, OJ 1991, 177; T 212/88, OJ 1992, 28; T 772/89) He may even recognise and rectify errors in the description on the basis of such knowledge (T 206/83, OJ 1987, 5; T 171/84, OJ 1986, 95; T 226/85, OJ 1988, 336). Textbooks and general technical literature form part of the common general knowledge (T 171/84, T 51/87, T 580/88, T 772/89). Common general knowledge does not normally include patent literature and scientific articles (see T 766/91, point 8.2 of the Reasons; T 1253/04, point 10 of the Reasons; both cited in T 2059/13, a decision concerning therapeutic use of a chemical compound in which the board also examined the possible role of post-published evidence). Information which can only be obtained after a comprehensive search is likewise not to be regarded as part of the common general knowledge (T 206/83, T 654/90). According to the board in T 475/88, a disputed claim of common general knowledge must be backed up by evidence. As a rule, demonstrating that the knowledge in question can be obtained from a textbook or monograph will be sufficient.

In T 2305/11 the application did not give details of how to determine the essential feature (maximum solubility pressure of at most 1 000 bar), but the board accepted the appellant's argument that the skilled person knew of suitable methods. It nevertheless found that crucial information was missing because the application did not disclose that, in many cases, no maximum could be found, or how to proceed in those cases. No useful guidance could be found in the description, and the appellant had failed to show how the skilled person could use his common general knowledge to fill in the gaps in disclosure or overcome the lack of guidance.

In T 2004/14 (absorbent article), the board decided that, in the absence of any indication in the patent in regard to the method (and the test conditions) of determining the absorption capacity, the skilled person would not be able to reliably and repeatedly determine the crucial condition set out in claim 1. The blotter-method was not the only applicable test known by the skilled person and, even if it were, at least the value for the draining pressure to be applied in order to expel interstitial fluids would still be lacking. That, allegedly twenty-four patent publications disclosed the blotter-method did not convince the board since these patents were solely from two corporations. Moreover, it was likely that they would, when applying such a non-standardised blotter-method, perform the test under different conditions, which was exactly what standards aimed to avoid.

In accordance with the established case law (see e.g. T 206/83, T 1040/03), a detailed disclosure is not necessary if the skilled person, who has common general knowledge at his immediate disposal, is capable of putting the invention into practice without the burden of exercising inventive skill. This principle obviously extends to all variants encompassed by a claim (T 1018/05, cited also in T 2301/12 in respect of variants clearly outside the scope of practical application of the claimed subject-matter and values of a parameter not obtainable).

The patent must provide guidance enabling the skilled person to identify the process features decisive in overcoming a prejudice. The skilled person should not have to work this out himself (T 419/12).

T 1861/11 concerned an invention relating to user interfaces. The appellant (applicant) chose to disclose the invention by means of a conceptual metaphor, a so-called "3D motion user interface", and the relevant disclosure was very brief. In the circumstances of the case, the board decided that details that the skilled person would need were not disclosed (Art. 83 EPC not satisfied). Moreover, as a matter of principle, a deficiency in disclosure concerning the conceptual fundamentals of the invention could not be remedied without violating the restrictions codified in Art. 123(2) EPC.

Patent specifications cannot normally contribute to the sufficiency of the disclosure unless they are available to the skilled reader of the patent in question (T 171/84, OJ 1986, 95). By way of exception, however, patent specifications and scientific publications may be considered to form part of the common general knowledge where the invention is in a field of research so new that the relevant technical knowledge is not yet available from textbooks (T 51/87, OJ 1991, 177; see also T 772/89, T 676/94, T 1900/08, T 2196/15). In T 676/94 the board considered that the question whether or not the contents of a technical periodical formed part of the average knowledge of a skilled person when assessing sufficiency of disclosure, should be answered on the basis of the facts and evidence in each particular case.

References to DVB standards were found insufficient to meet the standards of Art. 83 EPC in T 1191/04. In T 417/13 the size of the PVC particles was an important feature. The particle size may vary to a large extent depending on the method of measurement. The description of the application provided only very limited information. The person skilled in the art had thus to rely on his common general knowledge for the selection of an appropriate method of measurement. The board 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. It was also decided that in this case the physical and mathematical facts about particle size measurements were notorious.

In T 1608/13 the board noted that a patent document is directed to the skilled person, who interprets it in the light of the common general knowledge in the technical field concerned. Consequently, it is not necessary for all the details of the invention to be specifically described in order for a disclosure to be sufficient. In the present case, in the absence of a description in the patent of a specific measuring method for determining the sieving coefficient of a membrane for the separation of toxic mediators from blood by haemofiltration, the skilled person would first look for applicable standards in the field, if present. Whether other methods for carrying out the measurements were available was not decisive as long as there was no evidence that the results in the specific field of the invention would be contradictory depending on the chosen method. The respondent (opponent) did not provide any such evidence.

In T 521/12 claim 1 could be given different interpretations, in particular, with respect to the relationship between the features of the claim preamble and the features recited in the characterising part. However, as the only issue was sufficiency of disclosure, an interpretation of the claim wording was required only as far as it was relevant for deciding whether Art. 83 EPC was complied with. It was therefore implicit, in the board's view, that the expression "portion of electronic information" in feature (g) could not cover any possible type and format of electronically stored data, but was to be given a meaningful interpretation determined by the function it was expected to perform in the context of the claimed subject-matter. The skilled person wishing to implement the claimed invention would therefore exclude as meaningless and not consistent with the teaching of the application any type of "electronic information" which because of its content and/or format was irrelevant, or unsuitable.

T 658/04 summarised the case law about what forms part of the common general knowledge. The board considered that an expert opinion submitted by the appellant (patent proprietor) which contained general considerations (not supported by verifiable facts) did not form part of the common general knowledge (see also chapter I.C.2.8.1 "Definition of common general knowledge"). See also T 842/14 (quoting G 1/92, OJ 1993, 277), which concerned the requirements that a chemical composition of a commercially available product designated by a trademark in the claim be part of the common general knowledge of the skilled person. See also T 2196/15 for an example of difficulties in proving the common general knowledge.

In T 443/11 the board noted that during the course of the proceedings the examining division had argued that claim 1 had to be taken literally. The board disagreed with this statement, since it was established case law of the boards of appeal that claims should be interpreted in the manner that they would be understood by a person skilled in the art. In the context before it the board considered that the skilled person would understand (mathematical operations implemented in electronic devices).

In T 1516/14 the board stated that the consideration as to whether or not a particular feature distinguished the claimed subject matter from the prior art, or indeed whether or not it was merely a statement of something that was inherently true, played no role in assessing sufficiency of disclosure. Nor was it for the board to speculate as to why a particular feature was added to the claim in examination proceedings. The subjective intentions of the patentee are relevant for the purposes of interpreting the claims only to the extent that these intentions were explicitly formulated in and therefore derivable from the patent specification itself. The board did not rely solely on internal logic or syntax of the claim to arrive at the conclusion that Art. 83 EPC was satisfied; referring a question in this respect to the Enlarged Board was not justified. See also chapter II.A.6.1. about the contribution of T 1516/14, concerning interpretation of claims and the skilled person's approach meaning as being a purely technical approach.