In its recent decision T 1669/21, the EPO has provided clear guidance on the sufficiency of disclosure (Art. 83 EPC) for inventions in the field of applied AI. The emphasis is on specifying input and output parameters and their relationships in a way that ensures a clear and plausible connection. Importantly, it’s not about providing actual datasets but about making the invention implementable by detailing input/output formats, their technical content, and their interrelations.
In AI, the quality of disclosed relationships between inputs and outputs is critical. Without meaningful real-world correlations, even sophisticated machine learning models fail to deliver, reinforcing the principle of “nonsense in, nonsense out.” The term “data science” underscores that great AI depends on solid, relevant data.
On the positive side, if input and output parameters are properly described (and claimed), the AI model itself can often be briefly specified in the description and defined broadly in claim 1, such as a “machine learning model.” This approach allows inventors to secure protection for a “blackbox” AI solution in applied AI, where the focus is on the AI’s application field rather than the model’s internal workings.
Key takeaways for developers, inventors and patent practitioners:
-
Input-Output Data: The Magic Sauce
-
Be Specific, at least in dependent claims:
If input is “production data” get granular: “temperature at Point X, pressure at Time Y, using Sensor Z.” Specificity wins here. Same for outputs—clearly define what your model predicts.
-
Explain the Process:
Share in the description how data is collected. What’s being measured? Where and when? What tools or sensors? Concrete details = happy examiners.
-
Correlation is Key:
Make it clear why your inputs predict your output. Got experiments or existing field knowledge? Use them. You don’t need to prove 99% accuracy, but you do need plausible reasoning (e.g., “Output A spikes when Input B changes”).
-
Brag About Your Novelty:
Found a new input-output relationship? Share it! A novel parameter or unique correlation can make the difference between rejection and getting your AI blackbox patented.
-
-
Training Data: Teach Your Model Well
-
Explain How It Learns:
Mention training methods in the description like “supervised learning,” the loss function, and any unique tricks.
-
Name the Source:
Where’s the training data from? If it’s the same as inference data, say so. For supervised learning, explain how it’s labeled.
-
Cover Real-World Variations:
Show your training data is diverse enough to handle real-world scenarios. No need for perfection—just demonstrate it’s realistic and covers relevant parameter variations. For example, if you model shall learn to distinguish between dogs, cats and humans, the described training data should cover all three.
-
-
Taming the AI Model
-
Don’t Be Too Vague:
Say “machine learning model” in claim 1. That’s still a blackbox, but can most probably dodge an over-breadth objection.
-
Show Some concrete Concepts:
-
Mention real-world stuff in the description like OpenCV, GitHub libraries, or basic architectures (e.g., CNN + classifier). This keeps it relatable for developers—and credible for examiners.
-
-
DIY if Needed:
-
Don’t have an implementation? No sweat! Just outline a simple AI model that matches your input and output. Remember, the bar is low: it just needs to work, not win Kaggle competitions.
-
-
Highlight What’s New:
-
Did you tweak the input layer or discover a cool new feature? Explain it! Novel AI features aren’t just good for Art. 83—they boost your inventive step argument too.
Let’s have deeper look into the decision:
Summary of T 1669/21:
In decision T 1669/21, the EPO Board of Appeal confirmed the revocation of EP patent EP 2 789 960 B1 due to insufficient disclosure under Art. 83 EPC. The patent, which pertained to an applied AI invention, was initially revoked following opposition. The patentee’s appeal was rejected, as the Board found that the invention was not sufficiently disclosed to enable the skilled person to implement it.
The decision provides significant guidance on the requirements for sufficient disclosure (Art. 83 EPC) concerning inventions in applied AI (cf. the related article on Patentability of AI – Part 3: Claim directed to technical application field (“Applied AI” / Dimension 2))
Some background to Art. 83 EPC:
According to Art. 83 EPC , “The European patent application shall disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art.”
Importantly, Art. 83 EPC refers to the entire patent (application) and not only to the claims or claim 1. Hence, also any information given by the specification (e.g. the description of figures) is to be considered.
As further stated by the EPC Guidelines in this context (cf. EPC GL F-III 1)
A detailed description of at least one way of carrying out the invention must be given. Since the application is addressed to the person skilled in the art, it is neither necessary nor desirable that details of well-known ancillary features are given, but the description must disclose any feature essential for carrying out the invention in sufficient detail to render it apparent to the skilled person how to put the invention into practice. A single example may suffice, but where the claims cover a broad field, the application is not usually regarded as satisfying the requirements of Art. 83 unless the description gives a number of examples or describes alternative embodiments or variations extending over the area protected by the claims.
Hence, according to the EPC Guidelines a single embodiment which provides concrete details about the new aspects of the claimed invention can be sufficient to fulfill Art. 83 EPC. However, in case claim 1 is very broad (like in the case of EP 2 789 960 B1), the claimed scope must be covered by various embodiments over its whole extent.
These guidelines are confirmed by the discussed decision T 1669/21.
The invention of EP 2 789 960 B1
EP 2 789 960 B1 refers to a method for determining the condition of a fire-resistant lining of a metallurgical melting vessel. The method uses a calculation model (such as a neural network, cf. granted claim 9) for this determination.
In particular, claim 1 according to the Main Request in the Appeal defines:
(1a) A method for determining the state of the refractory lining of a vessel containing the molten metal, wherein
(1b) data of this refractory lining (12), such as materials, wall thickness, type of installation and others are detected or measured and evaluated,
characterised in that
(1c) the following measured or established data of each vessel (10) are all collected and stored in a data structure, namely
(1d) the initial refractory construction of the inner vessel lining (12), such as materials, material properties, wall thicknesses of blocks and/or injected materials as maintenance data;
(1e) production data during use, such as amount of molten mass, temperature, composition of the molten mass or the slag and its thickness, tapping times, temperature profiles, treatment times and/or metallurgical parameters;
(1f) wall thicknesses of the lining after using a vessel (10), at least at points with the greatest degree of wear;
(1g) additional process parameters such as the manner of pouring or tapping the molten metal into or out of the vessel (10);
(1h) that a calculation model is generated from at least some of the measured or ascertained data or parameters of the maintenance data, the production data, the wall thicknesses and the process parameters, by means of which these data or parameters are evaluated by means of calculations and subsequent analyses;
(1i) wherein the calculation model is adapted from the measurements of the wall thicknesses of the lining (12) after a number of tappings by means of a regression analysis,
(1j) by means of which the wear can be calculated taking into account the collected and structured data.
According to the Board, the features in red constitute input to the calculation model and features in green are the model’s output:
A closer look at the claimed method reveals two weaknesses:
- The “calculation model” is unspecified (only claim 9 mentions a neural network).
- The input data are described vaguely.
Additionally, the patent description is brief (two pages in the published version), which contributes to its revocation for insufficient disclosure. However, it is the quality and detail of the disclosure, not its length, that determines compliance with Art. 83 EPC.
The Board’s reasoning
The Board identifies multiple aspects of the claimed invention as not meeting the requirements of Art. 83 EPC, with particular focus on the input / output data of the calculation model.
Insufficient disclosure of the “Calculation model”:
The Board criticized claim 1 for failing to specify the type of calculation model, such as a machine learning model (cf. point 1.2.3). While claim 9 mentions a neural network, the patent provides no details about it—neither the network’s design, node arrangement, connections, nor activation functions.
Furthermore, while various neural network designs existed before the priority date, they were not tailored to the problem addressed by the invention (cf. point 1.3.4). This leaves the burden of selecting and configuring a suitable model entirely on the skilled person.
This objection seems justified, as the patent lacks any information about the model’s structure, not even generic boilerplate on a potential neural network architecture.
However, adding a brief description of a possible ML model or network design could have likely resolved this issue. Just as a mind game, imagine EP 2 789 960 B1 specified a concrete neural network design in its description, such as:
“The neural network may have several input branches, each dedicated to one type of data (e.g. refractory lining data, maintenance data, and process parameters). Each branch may have one fully connected layer with several nodes and ReLU activation, followed by a concatenation layer to merge the outputs. The concatenated output may then pass through two dense layers: the first with several nodes and ReLU activation, and the second with 1 node and a sigmoid activation function to output a predicted value between 0 and 1, representing the wall thickness.”
It remains speculative whether a short paragraph would have prevented the Board’s objection. However, including such a paragraph would likely have made it more challenging for the Board to revoke the patent due to insufficient disclosure of the model / neural network.
How to avoid Art. 83 objections against the claimed AI model
- Limit the AI model in dependent claims:
If claim 1 refers to a generalized “AI model,” add fallback positions in dependent claims or the description, such as “machine learning model,” “deep learning model,” or “neural network,” to address any concerns about over-breadth, as seen in T 1669/21.
- Specify the AI model in the description
Provide at least one specific embodiment of the model in the description:
-
- Check if the invention uses software modules from public toolboxes or repositories (e.g., OpenCV, GitHub). If so, mention these modules briefly as an example. Consider whether alternative modules or basic model architectures (e.g., CNN with classifier) could serve the same purpose. This is common, as most developers today apply existing AI models to new technical problems, rather than creating models from scratch.
- If you’re unsure how to implement the invention or which tools to use, create your own solution! Under Art. 83 EPC, sufficient disclosure only requires that the implementation works, not that it’s perfect. Focus on defining your input data, the required output, and design a model that matches input and output. See example above.
- Focus on new aspects of the AI model
Emphasize the novel aspects of the model (if any). For instance, if using an existing AI model but modifying its input layer for your specific data, provide a detailed description of these adaptations. Remember, it’s not just about meeting Art. 83 EPC requirements, but also addressing the inventive step. Highlight any innovative features in detail, as they could serve as fallback positions to differentiate your claim from prior art.
Insufficient disclosure of the input data
No specification of concrete input parameters
Although claim 1 outlines the inputs to the calculation model (i.e., refractory lining data, maintenance data, and process parameters), the Board argues that these are defined as categories rather than specific parameters. The Board contends that the input is overly broad, using generic terms that encompass many possible concrete measurements. Additionally, some of these parameters are time-variable, necessitating clarification of when (e.g., during which stage of the production process) the measurements should be taken. This deficiency is highlighted by the Board, for example, in point 1.6.2 of the decision:
“The patent does not contain any information or a single example of which specific measurements could be selected within the categories or are particularly meaningful for wear”.
Hence, the Board emphasizes that the specification of concrete measurements, i.e. of measured physical values, as input data to the model would be required.
This aligns with the EPC’s requirement for the technical character of computer-implemented inventions. By meeting the Art. 83 requirements as outlined in T 1669/21, the technical character and inventive step of the claimed invention can also be reinforced, as supported by EPC case law (e.g., D-I 9.2.4)
This view by the way matches with the EPC’s requirement to the technical character of a computer implemented invention. Hence, by fulfilling the Art. 83 requirements as outlined by the Board in T 1669/21, also the technical character / inventive step of the claimed invention can be strengthened, cf. e.g. EPC case law, D-I 9.2.4:
A technical character results either from the physical features of an entity or (for a method) from the use of technical means (T 641/00, OJ 2003, 352, T 1543/06).
According to T 208/84 (OJ 1987, 14), one indication of technical character is that the method has an overall technical effect, such as controlling some physical process (see also T 313/10).
Correspondingly, EPC GL G-II 3.3 sates in context of mathematical methods:
“If steps of a mathematical method are used to derive or predict the physical state of an existing real object from measurements of physical properties, as in the case of indirect measurements, those steps make a technical contribution regardless of what use is made of the results”.
Likewise, EPC GL G-II 3.3.2 states in context of simulations:
“Computer-implemented simulations that comprise features representing an interaction with an external physical reality at the level of their input or output may provide a technical effect related to this interaction. A computer-implemented simulation that uses measurements as input may form part of an indirect measurement method that calculates or predicts the physical state of an existing real object and thus make a technical contribution regardless of what use is made of the results”.
No relationship disclosed between input parameters and predicted output
he Board further emphasizes the need to plausibly demonstrate that the disclosed input parameters (if they were provided in the patent) are relevant for predicting the wear of the refractory lining. In particular, as stated at the end of point 1.6.5, the patent shall at least disclose the most relevant input parameters (implying that it is not required to disclose all howsoever relevant parameters).
In this context, a concrete embodiment should show that the input parameters enable a fundamentally successful prediction of the wear of the refractory lining. In my view, “fundamentally successful prediction” means that the prediction should be generally correct, i.e. more often right than wrong. However, the Board does not seem to require concrete evidence, such as experimental data or quantitative benchmarking of model accuracy.
The Board rejects the Patentee’s argument that the model can independently learn during training which input parameters are relevant for a successful prediction. Even though the skilled person is able to identify numerous input parameters, relevant input parameters might be missing, as the patent does not reveal the relevant ones. Consequently, no reliable correlation could be made by the trained model between the fed input parameters and actual wear of the refractory lining.
I agree with the Board’s insistence on the importance of disclosing these relationships. Essentially, the Board relies on the critical role of data science in AI. In machine learning (AI), it is essential that the input data is meaningfully correlated with the output (i.e., the parameter to be predicted) in the real world. AI models merely learn to capture and model these correlations to identify patterns in the input data. If no correlation exists between the chosen input parameters and the output, even the most sophisticated AI model cannot yield accurate results (aka “nonsense in, nonsense out”). This fundamental reliance on data is why the field is aptly named “data science” rather than “AI science”.
How to avoid Art. 83 objections against the claimed input/output data
- Limit the input data in dependent claims:
If claim 1 refers to generalized input categories, add some concrete parameters as fallback positions in the dependent claims. No need to say that also the model output should be briefly specified.
- Describe specific input parameters and how they are obtained
Add at least one concrete and workable embodiment which specifies concrete input parameters to the model.
-
- Provide a detailed explanation of how the input parameters are obtained, focusing on the physical process involved. Specify the physical properties represented by these parameters, including when, where, and how they are measured, and the type of sensors or devices used. Emphasize that these physical properties underpin the technical character of the invention, contributing to its inventive step.
- In this context, a “workable embodiment” means providing the skilled person with concrete guidance or instructions, ensuring they do not need to figure out all relevant details independently to implement the claimed invention.
- Describe the relationship between input and output
Explain why the disclosed input parameters are actually the most relevant ones to predict the model’s output.
-
- The reasoning should be plausible, and explicit evidence, such as experiments, is generally not required. While proving the model’s accuracy through benchmarking is not necessary (but can be advantageous), it should be plausible that the model’s predictions are basically correct (i.e. rather right thang wrong).
- In this context ”plausible reasoning” shall mean, either the correlation between the claimed inputs and outputs of the model is established in the prior art or the patent description provides at least implicit reasoning for the correlation, such as technical field knowledge or tests conducted by the applicant.
- Focus on new aspects of the input / output data
Highlight the novel aspects of the input/output data and their relationship. For example, if your model uses a new input parameter or uncovers a new connection between an input and the predicted output, describe these relationships in detail. This is crucial not only for meeting Art. 83 EPC but also for addressing inventive step. Ideally, the EPO will recognize the relationship as novel and inventive, allowing you to secure a patent with an AI “blackbox” approach, offering strong protection since input/output relationships are often easier to detect than internal model properties.
Insufficient disclosure of training data
The Board further objects that the training data, including its origin and properties, is insufficiently disclosed. As a result, it is not plausibly demonstrated by the patent disclosure that the trained calculation model can reliably predict the wear of the refractory lining.
While the Board’s reasoning appears both technically and legally questionable, it offers clear takeaways. I will focus on the key lessons learned from the Board’s reasoning before addressing its shortcomings in detail.
How to avoid Art. 83 objections against the disclosed training data / training method
- Briefly Explain the Training Method:
Indicate how the model is trained, e.g. by supervised learning, and if applicable, specify any unique aspects, such as the preferred loss function used during training.
- Specify the Training Data Source:
Identify the origin of the training data (as required by the Board in point 1.7.1). If the training data are obtained in the same way as the input data during inference (e.g. using the same measuring techniques / sensors), simply mention this. Indicate how the training data are labelled (for supervised learning).
- Relate Training Data to Intended Application:
Clarify that the training data are obtained (measured) to cover representative variations that span the parameter space relevant to the intended application. For instance, depending on the application’s scope, the training data could be collected from diverse sites or under varying process conditions. Additionally, highlight that measured data naturally include variations across individual parameters due to inherent measurement differences, as no parameter is artificially fixed.
If the data origin is properly explained, many of the Board’s objections regarding the training data may no longer be relevant.
Challenging the Board’s Reasoning on Training Data Disclosure Requirements
The Board argues that training data collected during normal steel plant operations would lack sufficient variation, potentially leading to undesirable learning of random correlations (see, e.g., point 1.7.5). However, this perspective needs technical refinement. It is not strictly necessary for training data to exhibit large variations if appropriate techniques are applied. For example, methods like contrastive learning with a triplet loss can enhance model training by focusing on relative relationships, even when data variation is limited. Such approaches enable models to generalize beyond the immediate dataset. It is worth noting, however, that the patent itself does not elaborate on the training process, including the loss function.
Beside this, the Board’s objection that insufficient variation in the training data prevents “successful training” (cf. point 1.7.5) appears misplaced in view of Art. 83 EPC. Art. 83 EPC focuses on whether the claimed invention is implementable and functional in principle, rather than on achieving satisfying (successful) training performance.
To illustrate this distinction, consider a binary classifier designed to differentiate between acceptable and excessive wear of refractory lining. If the classifier achieves an accuracy of 50.1% after training, this may be deemed a poor, i.e. unsuccessful training outcome. However, the model still demonstrates basic functionality by statistically outperforming random guessing. Therefore, it satisfies the requirements of Art. 83 EPC, which demands feasibility and basic operation rather than a specific performance level. This example underscores that Art. 83 EPC imposes a qualitative standard: the invention must work, even if imperfectly, rather than meet a high-performance threshold.
Thus, the Board’s concerns about the success of training (cf. point 1.7.5) seem to overstate the requirements for compliance with Art. 83 EPC. Limited variation in the training data might lead to a model with low accuracy or robustness, but it would anyway work in compliance with Art. 83 EPC.
Title photo: Highlighting the transition from vague to precise measurement data what counts for a strong patent. Left image: Predicting the state of a cheese fondue vessel employing rather vague and far-fetched measurement concepts. Right image: The JET magnetic fusion experiment, demonstrating the use of precise measurement parameters taken from its doughnut-shaped vessel (image under Creative Commons Attribution-Share Alike 3.0 Unported license). Note: Neither vessel relates to the one described in EP 2 789 960 B1.