Prepare legacy Paper C as a claim-mapping exercise. Anchor each objection in an Article 100 ground (patentability, insufficiency, or extension under Article 100(c), which covers both added matter under Article 123(2) and scope extension under Article 123(3)), map every claim feature to a single prior-art disclosure for novelty or to a problem-solution argument for inventive step, and test each auxiliary request under both amendment tests. A matrix you can update as the case shifts is more valuable than polished prose written early.
Anchoring every objection in a ground that Article 100 actually allows
An opposition may be founded only on the grounds of Article 100 EPC: patentability under Article 100(a), insufficiency under Article 100(b), and extension of subject-matter or scope under Article 100(c), which covers both added matter under Article 123(2) and scope extension under Article 123(3).
Start every mock opposition by labelling each objection with its ground. Article 100(a) covers Articles 52-57, including excluded subject-matter such as methods of treatment. Article 100(b) attacks whether the skilled person can carry out the invention across the whole claimed scope. Article 100(c) is the home ground for both amendment objections: added matter, because the subject-matter extends beyond the application as filed, and claims broader than granted. Any objection without a label is an objection you cannot defend, and noticing that in practice costs far less than noticing it in the exam.
Clarity is the classic trap to decide deliberately. Article 84 does not appear in Article 100, so a granted claim cannot fall on clarity; clarity of amendments is examined only within limits, following established case law such as G 3/14. Deciding early what each ground can and cannot reach keeps your skeleton argument clean. Use the table below as a mapping reference, then check every drafted objection against it before writing a single sentence of argument. Administrative details of the examination itself, including format and enrolment, belong to the EPO and are best confirmed at epo.org rather than from study material.
| Ground | Legal basis | What it attacks | What it does not attack |
|---|---|---|---|
| 100(a) - patentability | Art. 54, 56, 57; Art. 52-53 | Novelty, inventive step, industrial applicability, excluded categories | Clarity of granted claims; support |
| 100(b) - sufficiency | Art. 83 | Whether the skilled person can carry out the claimed invention across its scope | Pertinence of prior art; elegance of the invention |
| 100(c) - extension | Art. 123(2) and Art. 123(3) | Subject-matter extending beyond the application as filed; claims broader or differently scoped than granted | Clarity; pertinence of prior art |
| Not a ground | Art. 84 | Nothing in opposition against granted claims | Used only within limits for amendments |
Mapping claim features before drafting a single argument
For a novelty attack, every feature of the claim under attack must be found in one single prior-art disclosure. Build a feature-by-feature map first: claim elements in rows, documents in columns, and mark each cell as disclosed, not disclosed, or arguable.
The mapping habit exposes the gap between claim language and embodiments. A granted claim often uses broader wording than the examples in the description, so the question is what the claim actually covers, not what the marketed invention does. Write each claim feature as a short phrase in its own row, quote the exact passage you rely on in the matching cell, and resist the temptation to argue: the map should show the position in minutes.
The map also disciplines your attack choice. If D1 discloses all features except one, your novelty case fails and the argument shifts to inventive step combining D1 with D2. If two documents must be merged to reach the claim, you are squarely in problem-solution territory and should say so explicitly rather than dressing a combination as novelty. Practise this transition on mock claim sets until deciding which route to take feels mechanical rather than intuitive.
Small scenario: a claim recites a fastener of polymer P. Your map shows D1 discloses metal fasteners and the description only exemplifies polymer P once. Do not argue D1 anticipates the claim; instead flag the feature as the distinguishing feature and carry it forward, checking whether any effect is tied to it.
Running the problem-solution approach so the argument survives rebuttal
Structure inventive step in named steps: select the closest prior art, identify distinguishing features, derive the objective technical problem from the effect those features achieve, and ask whether the skilled person would have modified the closest art with that problem in mind.
Worked scenario 1. A paper patent claims a battery electrode with a porous current collector whose pores grow in size from one face to the other. D1 discloses a porous collector of uniform pore size. D2 teaches size gradation in filter media to improve particle retention. A plausible first move is to assert the combination is obvious because both documents concern porous structures. That reasoning does not survive rebuttal: the patentee responds that gradation in a filter serves particle capture, not electrode cycling, and the argument collapses because no objective technical problem was ever derived.
The better decision is to work the steps explicitly. Closest prior art: D1, same purpose and most shared features. Distinguishing feature: the pore-size gradient. Technical effect: plausibly improved adhesion of the active layer under cycling stress, drawn from the patent's description. Objective technical problem: provide a current collector with improved active-layer adhesion. Then test whether D2, which achieves gradation for a different mechanical purpose, would prompt that modification with the problem in mind. The conclusion may still favour you, but now the argument is reusable: when the patentee amends the claim later, the same skeleton absorbs the change.
Why it matters: an opposition is a case that moves through several requests, and a one-line 'both are porous, therefore obvious' cannot be patched once the claim text moves. A structured problem-solution skeleton can.
Screening each auxiliary request twice: added matter and scope
Treat every amended request as failing until tested twice: under Article 123(2) for direct and unambiguous disclosure of the amendment in the original application, and under Article 123(3) for not extending the scope of protection beyond the granted claims. Both tests sit under the Article 100(c) ground.
Worked scenario 2. The patentee files an auxiliary request importing a preferred-embodiment limitation into claim 1 and, in the same stroke, generalises the term 'container' in another clause to 'receptacle'. A plausible mistake is to attack only the generalisation as added matter and concede the limitation. That splits your case in two: you may win the 123(2) point on 'receptacle' while the imported limitation destroys your inventive-step argument on the amended claim.
The better decision applies both tests in order and then re-runs your attack matrix on the amended claim. First, is the combination of imported features directly and unambiguously disclosed as a single teaching, or stitched together from separate embodiments so that it creates new subject-matter? Second, following the relationship established in G 2/10, does the amendment narrow what is protected, so that infringement of the amended claim necessarily infringes the granted claim? Then update the map: the limitation may remove your D1-only novelty route while leaving your inventive-step route intact, which changes which request you fight hardest.
Why it matters: reasoning written in reusable, feature-level form can be re-aimed at each request; reasoning tied to one claim wording cannot. Also track admissibility separately, since late-filed amendments by a party face their own admissibility assessment distinct from allowability.
Separating sufficiency, added matter and exclusion objections cleanly
Insufficiency asks whether the skilled person can perform the invention across the whole claimed scope; added matter asks what the application as filed disclosed; exclusions ask whether the claimed subject-matter falls in a barred category. These overlap in the papers but have different tests.
An Article 100(b) attack needs a concrete gap: a feature the skilled person could not implement without undue burden, typically shown by explaining what technical work would be needed to obtain a claimed effect across the full scope. By contrast, an Article 123(2) attack under Article 100(c) needs a comparison with the application as filed, showing that the claim now teaches something the original disclosure did not. Conflating them weakens both: 'the effect is not plausible across the whole scope' is a sufficiency shape, not an added-matter shape, and each requires different evidence.
Exclusions sit under Article 100(a) and require reading the claim as a whole. A claim dressed as a device may in substance define a method of treatment, or a computer-implemented claim may in substance define a program as such; the analysis asks what the claimed features actually achieve. Practise writing short, separate objection blocks, each with its ground, its test, and its evidence, and practise stating in one sentence why each objection is not better made under a different ground. That discipline of placement is itself teachable and testable on mock sets.
Interpreting claim terms the way opposition practice reads them
Read claim terms so the description and drawings inform them without rewriting them: a term can take context-specific meaning, but the claim itself defines the protection, as Article 69 EPC and its Protocol confirm. Interpretation choices decide novelty outcomes.
Two opposite errors recur in practice. The first reads a preferred embodiment into the claim, shrinking it artificially; if the claim says 'fastener' and one example uses a rivet, the claim is not limited to rivets, and your novelty attack must address the broader term. The second stretches a claim term to escape prior art, which the patentee cannot do and which you should anticipate being policed. In both cases the description anchors the meaning without replacing the claim text.
In a Paper C setting, decide interpretation explicitly and early, and note the choice in your attack matrix, because your novelty and inventive-step conclusions depend on it. Practise with two-colour annotation: one colour for what the claim text necessarily requires, one for what the description merely suggests. Where the two colours disagree, write down which reading you adopt and why. Over a set of mock claims, this produces a consistent construction policy you can apply under time pressure instead of re-deciding each case from scratch.
Small scenario: the claim recites 'annealed' metal, and the description defines annealing as heating above 400 degrees in one embodiment. If the claim lacks the temperature, treat the value as an example, not a claim feature, and check whether any document discloses the unbounded term before arguing a temperature-based attack.
A preparation sequence and a self-check rubric you can reuse
Sequence practice in four passes: claim mapping on mock grants, single-document novelty attacks, problem-solution essays on multi-document cases, then full amendment screening under time. Score each pass against the rubric below; the numbers are learning milestones, not pass predictions.
Practical exercise: take any mock granted claim set, or construct one by adapting a published patent into a paper scenario. Build the attack matrix: claim features in rows, documents and requests in columns, grounds recorded per objection. Expected observations when you do it well: every row has at least one filled cell or a stated reason why it is unfilled; every objection carries exactly one ground label; every auxiliary request carries both amendment-test verdicts; and you can restate your inventive-step skeleton for the amended claim 1 in five bullet points without re-reading the documents.
Self-check rubric: score 1-3 on each item: grounds correctly labelled; feature mapping complete and quoted; objective technical problem derived from a stated effect; amendment tested under both 123(2) and 123(3); construction decision stated explicitly. A total of 13-15 across repeated attempts suggests the reasoning structure is holding; lower totals tell you which pass of the sequence to repeat. A sensible adaptable plan: several sessions of mapping-only drills, then timed novelty and inventive-step essays, then one full opposition where you deliberately re-aim your case at a new auxiliary request mid-exercise.
Readiness checks before the paper: reproduce the Article 100 grounds list and the clarity limitation from memory; produce a complete problem-solution argument from a fresh claim set within a self-set time limit; and demonstrate that any amendment you meet receives both amendment tests before you argue patentability. Administrative questions go to the EPO at epo.org.
- Rubric item 1: every objection carries exactly one correct Article 100 ground label
- Rubric item 2: feature map complete, with quoted passages per cell
- Rubric item 3: objective technical problem derived from a stated technical effect
- Rubric item 4: each auxiliary request tested under both 123(2) and 123(3)
- Rubric item 5: claim-construction decision recorded explicitly before attacking
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.