According to the boards' established case law, a prior art document anticipates the novelty of claimed subject-matter if the latter is directly and unambiguously derivable from that document, including any features implicit to a person skilled in the art. However, an alleged disclosure can only be considered "implicit" if it is immediately apparent to the skilled person that nothing other than the alleged implicit feature forms part of the subject‑matter disclosed (T 95/97, T 51/10). In other words, a prior art disclosure is novelty-destroying if the subject-matter claimed can be inferred directly and unequivocally from that disclosure, including features which for the skilled person are implicit in what is explicitly disclosed (see T 677/91; T 465/92, OJ 1996, 32; T 511/92; and T 2170/13, which is a more recent decision finding that the feature at issue was implicitly disclosed in the prior art and devoting lengthy technical arguments to the point.

The limitation to subject-matter "derivable directly and unambiguously" from the document is important. According to the boards' case law on assessing novelty, the teaching of a document, independent of its nature, is not to be interpreted as embracing equivalents not disclosed in that document (see also T 167/84, T 517/90, T 536/95). This is a matter of obviousness (see Guidelines G‑VI, 2 – November 2018 version).

In T 701/09 the board found that direct and unambiguous disclosure was not limited to explicit or literal statements, but equally included implicitly disclosed information which a reader skilled in the art would unequivocally gather from the overall context of a cited document.

In T 1523/07 the board observed that it is a generally applied principle that for concluding lack of novelty, there must be a direct and unambiguous disclosure, either explicit or implicit, in the state of the art which would inevitably lead the skilled person to subject-matter falling within the scope of what is claimed. In this context "implicit disclosure" means disclosure which any person skilled in the art would objectively consider as necessarily implied in the explicit content, e.g. in view of general scientific laws. In this respect, the term "implicit disclosure" should not be construed to mean matter that does not belong to the content of the technical information provided by a document but may be rendered obvious on the basis of that content. Whilst common general knowledge must be taken into account in deciding what is clearly and unambiguously implied by the explicit disclosure of a document, the question of what may be rendered obvious by that disclosure in the light of common general knowledge is not relevant to the assessment of what is implied by the disclosure of that document. The implicit disclosure means no more than the clear and unambiguous consequence of what is explicitly mentioned (see T 823/96, T 297/11). Implicit disclosure means disclosure which any person skilled in the art would objectively consider as necessarily implied in the explicit content (T 2522/10 of 16 April 2015 date: 2015-04-16). T 1523/07 was cited in the recent case T 1085/13 (novelty of higher degree of purity).

In T 51/10 the board held, in summary, that, for a feature to be "implicit", it was essential that it could be unequivocally gathered from the overall context of a cited document (T 701/09) or necessarily followed from that context (T 1523/07). In particular, the skilled person had to be unable to conceive of any realistic alternative to the allegedly implicit feature (T 287/16).

In T 6/80 (OJ 1981, 434) the board found that where a further functional attribute of an element of a device disclosed in a document was immediately apparent to a person skilled in the art reading the document, such attribute formed part of the state of the art with regard to that device.

In T 666/89 (OJ 1993, 495) the board stated that the term "available" clearly went beyond literal or diagrammatical description, and implied the communication, express or implicit, of technical information by other means as well. One example of the available information content of a document extending beyond this literal descriptive or diagrammatical content was the case where the carrying out of a process, specifically or literally described in a prior art document, inevitably resulted in a product not so described. In such a case the prior art document would deprive a claim covering such a product of novelty. It was thus content, express and implied, rather than mere form, that was decisive for the issue of novelty in general, and "selection" novelty in particular (T 793/93).

In T 270/97 the opposition division considered the claimed product to be anticipated by the agent produced and inevitably obtained by repeating examples 1 and 2 of a prior art document. The board noted that it was a well-established principle laid down in the case law since T 12/81 (OJ 1982, 296) that the product inevitably resulting from a process properly defined as to its starting substance and reaction conditions was considered to be disclosed even if it was not cited expressis verbis in the prior art document. The board, however, found that the method disclosed in the text of example 2 implied a way of acting not envisaged in the method according to the patent in suit. The parties' attempts to show that the particles obtained according to example 2 were, or were not, identical to the products of the patent in suit, produced highly contradictory results. Therefore, the board could only conclude that depending on experimental conditions not disclosed in example 2 different products might be obtained. Thus, the claimed product was not inevitably obtained by following the method of example 2.

In T 583/01 the board, following T 270/97, stated that novelty was a question of inevitability and not a question of probability.

The patent at issue in T 1456/14 was for a vacuum cleaner with a filter and its claim 1 was directed to the proportion of total length to area. That no total length was disclosed in the cited prior-art document was, the board held, irrelevant for the purposes of assessing novelty if it could be demonstrated that it undoubtedly covered the claimed proportion nonetheless. To do so, it sufficed to show that even a smaller numerical value necessarily exceeded by the prior-art device would be in keeping with the claimed proportion, as this meant the prior-art document definitely had to encompass that proportion too. Whether a known device had an implicit (or even explicit) feature did not depend on whether or not the skilled person's attention was likely to be drawn to precisely that feature but on whether, from a purely objective perspective, it had to have that feature. For the criterion of "direct and unambiguous disclosure" to be met, it was not essential that the skilled person would realise the feature was included even without knowing about the patent. EPO departments were to examine disclosure with the eyes and understanding of the skilled person, but that did not mean they did not do so purposively, in full knowledge of the feature they were looking for. Such an approach did not amount to an impermissible consideration of equivalents.

In T 518/91 the board held that the logical interpretation by a skilled person of technical facts explicitly stated in a prior document – in particular the definition beyond the explicit disclosure of the document of features of the prior art described in general terms – was not part of the technical teaching implicitly derivable from the document, which the skilled person would automatically infer, if it contradicted other explicit technical information in the otherwise consistent overall disclosure of the document.

In T 2387/13 (no implicit disclosure of a possible use) the board stated that the mere fact that the disclosed electrical transmission line in D2 could be used as a sensor did not mean that a sensor was disclosed. In order for such a use to be possible, there would have to be further installations. Such installations were, however, not disclosed.

In T 624/91 it was held that exact disclosures for alloy compositions in the state of the art had to be interpreted as average or nominal values within a small range in view of known fluctuations in reproducibility and in analytical results, unless there was evidence available to the contrary. The board pointed out that, whenever a metallurgist aimed at producing an alloy in accordance with a given nominal composition, the composition of the final product would deviate somewhat from this target or even be undefined within certain narrow limits. The metallurgical production process was not ideally reproducible and the actual composition of different batches aiming at the same nominal composition would be spread over a certain area around this target (see also T 718/02, T 324/12).

In T 71/93 it was held that a feature not explicitly mentioned in a prior art document, even though generally known to help overcome a drawback usual in the same technical field, could not be considered implicitly disclosed if it were not directly derivable from the prior art document that the drawback was considered unacceptable and/or if other solutions were proposed for overcoming the drawback.

In T 572/88 and T 763/89 the boards warned against using the concept of "implicit prior description" in such a way that considerations relevant to the evaluation of inventive step were transferred to the assessment of novelty. A fair assessment of an invention's patentability called for a clear distinction between novelty and inventive step. In decision T 763/89, for example, the opponent could not claim "implicit prior description" for a material with exactly three layers, as claimed in the disputed patent, on the grounds that a skilled person, aware of the considerable outlay required for further sub-layers and the limited improvement in the quality of the image they bring, would have understood the wording of the claim, which set no upper limit for the number of layers, to be virtually synonymous with "two or three layers". To do so would be to adduce a typical criterion for the evaluation of inventive step.

Likewise in T 71/93 the board held that an "implicit prior description" of a feature could not be based on the grounds that a person skilled in the art would have been aware of some disadvantages and of the lack of other forms of improvement related to a feature, since this was a criterion for the evaluation of inventive step.