REVIEW 3 major objections 3 minor 45 references
Uninorms via two comparable closure operators on bounded lattices
T0 review · 3 major / 3 minor · reviewed 2026-08-15 · deepseek-v4-flash
Pith's one-line read With two comparable closure operators, a piecewise operation on a bounded lattice is a uninorm exactly when both operators keep their outputs out of [e,1].
desk verdict The main two-operator construction is new and Theorem 3.1's proof mostly holds, but the paper's showcase example is invalid and the dual theorems are unproved. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the piecewise operation $U$ built from a t-conorm on $[e,1]$ and two closure operators assigned to the two lower blocks of the lattice, namely $]0,e[$ and the set $I_e$ of elements incomparable with $e$. Closure operators are the monotone, inflationary, idempotent maps; their defining identity $cl(cl(x)\wedge y)=cl(x)$ whenever $x\le y$ is what makes the crossed terms $cl_i(x)\wedge(x\vee e)$ associate correctly. The comparability condition $cl_1\le cl_2$ on $L\setminus[e,1]$ orders the block outputs, and the exclusion conditions $cl_1(x)\notin[e,1]$ and $cl_2(x)\notin[e,1]$ force those outputs to stay inside the assigned blocks $]0,e[$ and $I_e$, respectively. Together these ingredients reduce a seemingly arbitrary binary operation to a four-block structure whose associativity can be checked block by block.
What would settle it
On a candidate finite lattice, compute $U$ as in Theorem 3.1 and test the two exclusion conditions. If some $x\in]0,e[$ has $cl_1(x)\in[e,1]$, then $U(U(1,x),x)=U(cl_1(x)\wedge(x\vee e),x)=x$ while $U(1,U(x,x))=U(1,0)=0$, so associativity fails; the analogous computation with $cl_2$ on $I_e$ refutes the dual condition. A single concrete lattice table exhibiting this failure would settle the claim by showing the conditions are truly necessary.
Extended reading notes
Core claim
For $e\in L\setminus\{0,1\}$, $S$ a t-conorm on $[e,1]$, and $cl_1\le cl_2$ pointwise on $L\setminus[e,1]$, the operation defined by $S$ on $[e,1]^2$, by $x$ or $y$ on the strips meeting $\{e\}$, by $cl_1(x)\wedge(x\vee e)$ on $]0,e[\times]e,1]$ and its transpose, by $cl_2(x)\wedge(x\vee e)$ on $I_e\times]e,1]$ and its transpose, and by $0$ elsewhere, is a uninorm with neutral element $e$ if and only if the two exclusion conditions hold. The necessity is detected by associativity at the triple $(1,x,x)$: if $cl_1(x)\in[e,1]$, then $U(U(1,x),x)=x$ whereas $U(1,U(x,x))=0$. The sufficient direction splits $L$ into the regions $]0,e[$, $\{e\}$, $I_e$, and $]e,1]$, checks increasingness case by case using $cl_1\le cl_2$, and proves associativity with the closure identity $cl(cl(x)\wedge y)=cl(x)$ for $x\le y$. The dual interior-operator theorems mirror the construction on $[0,e]$ with a t-norm, meet replaced by join, and $1$ as the absorbing value.
Load-bearing premise
The argument leans on the premise that $cl_1(x)\le cl_2(x)$ for every element outside $[e,1]$; the monotonicity proof moves inequalities from one block to the next through this chain, and without that comparability the necessary-and-sufficient characterization is not established.
Editorial extensions
If this is right
- When both closure operators are the identity map, the construction in Theorem 3.1 reduces exactly to the standard uninorm $U_s$ built from $S$ on $[e,1]$ and $0$ elsewhere.
- Setting only $cl_1$ to the identity yields a single-closure-operator uninorm that lies in $U_{\min}^{*}$ but not in $U_{\min}\cup U_{\max}^{r}$, as Example 3.2 demonstrates.
- For lattices whose interval $]0,e[$ is a singleton or is totally incomparable internally, the constructed uninorm belongs to $U_{\min}^{*}$, and the analogous structural condition places the Theorem 3.3 construction into $U_{\min}^{1}$.
- When the top element is made absorbing in Theorem 3.3, the extra condition $S(x,y)<1$ for all $x,y\in]e,1[$ is forced, and it is exactly as necessary as the closure-operator exclusion conditions.
- The interior-operator mirrors, Theorems 3.2 and 3.4, produce the corresponding dual facts with a t-norm $T$ on $[0,e]$ and with $1$ or $0$ as the absorbing element.
Reading between the lines
- Beyond the paper: the same block-decomposition proof would work for any pair of increasing, inflationary, idempotent endomaps assigned to the two regions, so the result is likely a special case of a general two-monotone-block uninorm recipe.
- Beyond the paper: because the theorem is an if-and-only-if statement, a finite-lattice test needs only to check comparability and the two exclusion conditions, not all associativity triples, to certify that a proposed piecewise operation is a uninorm.
- Beyond the paper: replacing the top element $1$ by an arbitrary fixed element in Theorem 3.3 suggests a family of absorbing-point uninorms whose characterization would combine a condition on the t-conorm with the closure-operator conditions.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes constructions of uninorms on bounded lattices from pairs of comparable closure operators (Theorems 3.1 and 3.3) and, dually, pairs of comparable interior operators (Theorems 3.2 and 3.4), together with a t-conorm on [e,1] or a t-norm on [0,e]. The main result, Theorem 3.1, defines a piecewise operation U and characterizes, under the standing comparability assumption cl1(x) ≤ cl2(x) for x ∈ L \ [e,1], exactly when U is a uninorm with neutral element e: namely, cl1(x) ∉ [e,1] for all x ∈ ]0,e[ and cl2(x) ∉ [e,1] for all x ∈ Ie. Several degenerate cases with a single operator are derived, and the paper claims that the resulting uninorms need not lie in the previously studied classes U_min* ∪ U_min^1 or U_max* ∪ U_max^0. Examples and tables are provided to illustrate the constructions.
Significance. If the main theorems are correct, the construction is a genuine addition to the known toolkit: in contrast to earlier closure- and interior-operator based uninorms, the present values on the mixed region ]0,e[ × ]e,1] actually depend on the chosen operators, and the conditions on those operators are necessary and sufficient. The proof of Theorem 3.1 is largely detailed: the necessity arguments are clean, the associativity proof is organized by Proposition 2.3, and Lemma 3.1 is used appropriately. The paper also includes a useful consistency check: setting the operators to the identity recovers the Karacal-Mesiar uninorm. However, the significance is substantially tempered by the fact that the only displayed non-degenerate example is invalid, and the dual interior-operator theorems are stated without proof. The central theorem may well be correct, but the manuscript in its present form does not provide a reliable non-degenerate demonstration of the construction.
major comments (3)
- [Example 3.1 (Tables 1 and 2)] The closure operator cl2 in Table 1 is not a closure operator. Since a ∈ ]0,e[ and j ∈ ]e,1], axiom (CL2) applied to a and e gives cl2(a∨e) = cl2(e) = e, while cl2(a)∨cl2(e) = j∨e = j, forcing e = j, a contradiction; the same failure occurs for b. Moreover, Table 2 is not the operation defined in Theorem 3.1 for the stated operators: Table 2 has U(k,k) = k, which forces k ∈ [e,1], and U(m,m) = 0, so m ∈ ]0,e[ ∪ Ie; but for m ∈ ]0,e[ the theorem gives U(m,k) = cl1(m)∧e = k∧e = e, and for m ∈ Ie it gives U(m,k) = cl2(m)∧(m∨e) = k∧(m∨e) = m∨e ≠ 0, whereas Table 2 lists U(m,k) = 0. The example is therefore not a valid instance of Theorem 3.1 and cannot support the Conclusion's claim that nontrivial closure operators satisfying the hypotheses exist; it should be corrected or replaced.
- [Theorems 3.2 and 3.4] The dual interior-operator theorems are stated without proof. The abstract and the body advertise these results as part of the contribution, and the claimed characterizations (int2(x) ∉ [0,e] for x ∈ Ie and int1(x) ∉ [0,e] for x ∈ ]e,1[, together with 0 < T(x,y) in Theorem 3.4) are not verified by any argument. Calling these results 'dual' is not a substitute for a proof, because the constructions use different intervals and the necessity arguments for the interior-operator conditions require a separate check. Please supply the proofs or a precise order-reversal derivation from Theorems 3.1 and 3.3.
- [Theorem 3.3 proof] The sufficiency direction of Theorem 3.3(1) is only a sketch: it says that, taking Theorem 3.1 into account, it is enough to check the cases with 1 ∈ {x,y,z}, and then asserts monotonicity and associativity for those cases without demonstration. Since Theorem 3.3 differs from Theorem 3.1 by using [e,1[ in place of [e,1] for the t-conorm region and by making 1 absorbing, the extra condition S(x,y) < 1 is not merely cosmetic; its role in the sufficiency proof should be shown explicitly, including the mixed cases involving 1. Please expand this part of the proof or state clearly that it is a direct analogue with the same case analysis.
minor comments (3)
- [Theorem 3.1, monotonicity case 1.2.3] The inequality U(x,z) ≤ U(y,z) in case 1.2.3 is asserted without explanation; the reader should be shown the chain cl1(x)∧e ≤ cl2(y)∧e ≤ cl2(y)∧(y∨e), which uses the standing comparability cl1(x) ≤ cl2(x) and monotonicity of cl2. This is the one place where the comparability assumption is genuinely load-bearing.
- [Proposition 3.1] The phrase ']0,e[ ⊆ {x} for some x ∈ L' is awkward; it should be phrased as ']0,e[ is a singleton' or ']0,e[ = {x}'. The same applies in Propositions 3.3, 3.6, and 3.9.
- [Example 3.3 (Tables 4 and 5)] A similar consistency check to the one for Example 3.1 should be performed for Example 3.3. In particular, Table 5 has U(c,c) = c, which suggests c ∈ ]e,1[, but then cl2(l) = c and cl2(m) = c for l,m that appear to lie in Ie would violate the hypothesis cl2(x) ∉ [e,1] required by Theorem 3.3; the example should be recomputed or clarified.
Circularity Check
No significant circularity: the main characterization is proved from definitions, not derived from its own conclusion.
full rationale
The paper's central result, Theorem 3.1, defines a candidate operation U from a t-conorm S and two closure operators cl1, cl2 and proves an if-and-only-if characterization of when U is a uninorm with neutral element e. The necessity direction derives the conditions cl1(x) not in [e,1] for x in ]0,e[ and cl2(x) not in [e,1] for x in Ie from explicit associativity contradictions, e.g. U(U(1,x),x) = U(e,x) = x versus U(1,U(x,x)) = U(1,0) = 0. The sufficiency direction verifies monotonicity and associativity directly, using Lemma 3.1 and Proposition 2.3; the comparability assumption cl1 <= cl2 is a stated hypothesis used inside the proof, not a conclusion imported from outside. No parameter is fitted to the desired result and no quantity is 'predicted' from data that already determines it. The degenerate cases with cl1 = cl2 or identity closures reduce to the known Karaçal–Mesiar construction; this is explicitly described as a consistency check and does not bootstrap the main theorem. The authors' own prior works are cited only for context and not as load-bearing evidence for Theorem 3.1. Even the illustrative defect noted in Example 3.1's Table 1, where cl2 may fail axiom CL2, would be a correctness issue for an example, not a circular derivation. Consequently, no circular step can be identified in the paper's derivation chain.
Assumptions & free parameters
assumptions (6)
- standard math Classical set-theoretic mathematics with standard bounded lattice theory (order, meet, join, intervals).
- standard math Closure operators satisfy (CL1) x≤cl(x), (CL2) cl(x∨y)=cl(x)∨cl(y), (CL3) cl(cl(x))=cl(x) (Everett [20]).
- standard math Interior operators satisfy (IN1) int(x)≤x, (IN2) int(x∧y)=int(x)∧int(y), (IN3) int(int(x))=int(x).
- standard math Proposition 2.3 from Ji [28]: a commutative operation on a union of subsets is associative iff associativity holds on all local triples and mixed pairs.
- domain assumption A t-conorm S on [e,1] with neutral element e is given as input in Theorems 3.1 and 3.3.
- domain assumption The two closure operators are comparable on L\[e,1]: cl1(x) ≤ cl2(x) for all x∈L\[e,1].
Cite this review
Pith. "Pith review of Uninorms via two comparable closure operators on bounded lattices." pith.science (2026). https://pith.science/paper/2ENP6LHW
@misc{pith2026250504220,
author = {Pith},
title = {Pith review of: Uninorms via two comparable closure operators on bounded lattices},
year = {2026},
howpublished = {\url{https://pith.science/paper/2ENP6LHW}},
note = {Machine review of arXiv:2505.04220}
}
abstract
In this paper, we propose novel methods for constructing uninorms using two comparable closure operators or, alternatively, two comparable interior operators on bounded lattices. These methods are developed under the necessary and sufficient conditions imposed on these operators. Specifically, the construction of uninorms for $(x ,y )\in ]0 ,e [\times]e ,1 [ \cup ]e ,1 [\times]0 ,e [$ depends not only on the structure of the bounded lattices but also on the chosen closure operators (or interior operators). Consequently, the resulting uninorms do not necessarily belong to $\mathcal{U}_{min}^{*}\cup \mathcal{U}_{min}^{1}$ (or $\mathcal{U}_{max}^{*}\cup\mathcal{U}_{max}^{0}$). Moreover, we present the degenerate cases of the aforementioned results, which are constructed using only a single closure operator or a single interior operator. Some of these cases correspond to well-known results documented in the literature.
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