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Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Proof-search and countermodel generation fornon-normal modal logics
Gian Luca POZZATO
Progetti GNCS 2019, Hotel Belvedere, Montecatini Terme
13 febbraio 2020
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 1 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 2 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 3 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Non-normal modal logics
Generalization of ordinary modal logics that do not satisfy someaxioms or rules of normal modal logic K
Why NNMLAvoid the commitment to some logic principles that are theoremsof K but are not acceptable under possible interpretations of themodality:• Deontic• Epistemic• · · ·
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 4 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Non-normal modal logics
• Epistemic reasoning• 2A read as “the agent knows/believes A”• NNML offer a partial solution to the problem of omniscience
• 2B does not follow from 2A and 2A→ 2B• rejection of the rule of monotonicity: A→ B implies
2A→ 2B
• Deontic logic• 2A interpreted as “it is obligatory that A”• NNML offers solutions to some paradoxes
• Ross’ paradox• gentle-murder paradox
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 5 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Non-normal modal logics
Systems considered
E := CPL + A→ B B → ARE2A→ 2B
• Extensions:
M I 2(A ∧ B)→ 2A
C I 2A ∧2B → 2(A ∧ B)
N I 2>E
EM
EC EN
EMC EMN
ECN
EMCN (K)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 6 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 7 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Bi-neighbourhood semantics
Bi-neighbourhood modelsTriplesM = 〈W ,N ,V 〉• W is a non-empty set of worlds (states)• V is a valuation function• N is a bi-neighbourhood function W −→ P(P(W)× P(W))
such that (α, β) ∈ N (w) implies α ∩ β = ∅Intuition: α and β provide independent positive and negative evi-dence for A
Truth of 2Aw ∈ [2A] iff there is (α, β) ∈ N (w) such that
for all u ∈ α, u ∈ [A], and for all v ∈ β, v 6∈ [A]
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 8 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Bi-neighbourhood semantics
Model properties
C-models: (α1, β1), (α2, β2) ∈ N (w) implies(α1 ∩ α2, β1 ∪ β2) ∈ N (w)
N-models: (W , ∅) ∈ N (w) for all w ∈WM-models: (α, β) ∈ N (w) implies β = ∅
CompletenessLogic E(M,C,N) is sound and complete w.r.t. bi-neighbourhood(M,C,N-)models
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 9 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 10 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Desiderata
• Analytic• Standard
• Finite numbers of rules each one with finite and fixed numberof premises
• Modular• Fixed set of basic rules• Extensions obtained by adding suitable rules expressing
semantic properties
• Terminating• Optimal• Countermodel generation
• Obtain directly a countermodel from a failed proof search
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 11 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
The Sequent Calculi LSE∗
Labels• World labels x , y , z , ...• Neighbourhood labels a, b, c, ...
Neighbourhood terms• Positive terms [a1, ..., an] = finite sets of neighbourhood labels• Negative terms t, where t is a positive term• Neighbourhood constants τ , τ
Intuition• t and t are the two members of a pair of neighbourhoods• [a1, ..., an] ; a1 ∩ ... ∩ an [a1, ..., an] ; a1 ∪ ... ∪ an τ ; W
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 12 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
The Sequent Calculi LSE∗
Initial sequents: x : p, Γ ⇒ ∆, x : p x : ⊥, Γ ⇒ ∆ Γ ⇒ ∆, x : >x ∈ t, x : A, t ∀ A, Γ ⇒ ∆
L ∀x ∈ t, t ∀ A, Γ ⇒ ∆
x ∈ t, Γ ⇒ ∆, x : AR ∀
Γ ⇒ ∆, t ∀ A
x ∈ t, x : A, Γ ⇒ ∆L ∃
t ∃ A, Γ ⇒ ∆
x ∈ t, Γ ⇒ ∆, x : A, t ∃ AR ∃
x ∈ t, Γ ⇒ ∆, t ∃ A
[a] ∈ N (x), [a] ∀ A, Γ ⇒ ∆, [a] ∃ AL2
x : 2A, Γ ⇒ ∆
t ∈ N (x), Γ ⇒ ∆, x : 2A, t ∀ A t ∈ N (x), t ∃ A, Γ ⇒ ∆, x : 2AR2
t ∈ N (x), Γ ⇒ ∆, x : 2A
Mt ∈ N (x), y ∈ t, Γ ⇒ ∆
τ ∈ N (x), Γ ⇒ ∆Nτ
Γ ⇒ ∆Nτ
x ∈ τ, Γ ⇒ ∆
[a1, ..., an ] ∈ N (x), [a1] ∈ N (x), ..., [an ] ∈ N (x), Γ ⇒ ∆C
[a1] ∈ N (x), ..., [an ] ∈ N (x), Γ ⇒ ∆
x ∈ [a1], ..., x ∈ [an ], Γ ⇒ ∆dec
x ∈ [a1, ..., an ], Γ ⇒ ∆
x ∈ [a1], Γ ⇒ ∆ ... x ∈ [an ], Γ ⇒ ∆dec
x ∈ [a1, ..., an ], Γ ⇒ ∆
Application conditions:
x is fresh in R ∀ and L ∃, a is fresh in L2, and x occurs in the conclusion of Nτ .
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 13 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Examples of derivations
Axiom M..., y : A, y : B, y : [a], [a] : A ∧ B ⇒ y : A, ...
L∧..., y : A ∧ B, y : [a], [a] : A ∧ B ⇒ y : A, ...
L ∀..., y : [a], [a] : A ∧ B ⇒ y : A, ...
R ∀..., [a] : A ∧ B ⇒ [a] : A, ...
M..., y : [a], y : A, [a] : x ⇒ ...
L ∃..., [a] : A, [a] : x ⇒ ...
R2[a] : x, [a] : A ∧ B ⇒ x : 2A, [a] : A ∧ B
L2x : 2(A ∧ B) ⇒ x : 2A
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 14 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Example of failed proof search and countermodel
Axiom M in LSE∗
A cl.
A′ cl. y : [a], y : p, [a] : x, [a] : p ∧ q ⇒ x : 2p, [a] : p ∧ q, y : qL∧
y : [a], y : p, [a] : x, [a] : p ∧ q ⇒ x : 2p, [a] : p ∧ q, y : p ∧ qR ∃
y : [a], y : p, [a] : x, [a] : p ∧ q ⇒ x : 2p, [a] : p ∧ qL ∃
[a] : x, [a] : p ∧ q, [a] : p ⇒ x : 2p, [a] : p ∧ qR2
[a] : x, [a] : p ∧ q ⇒ x : 2p, [a] : p ∧ qL2
x : 2(p ∧ q) ⇒ x : 2p
saturated branch B
Bi-neighbourhood countermodelMW = {x, y} N (x) = {(α[a], α[a]
)} α[a] = ∅ V (p) = {y}N (y) = ∅ α
[a]= {y} V (q) = ∅
We have M, x |= 2(p ∧ q) and M, x 6|= 2p
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 15 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Results
AXIOMATICSYSTEMS E∗
SEMANTICSBi-neighbourhood
models
PROOF SYSTEMSLabelled calculi
Decision procedures
S.&C. Cut elim.
S. & C.
F.m.p. Saturation
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 16 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 17 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
PRONOM
Basic ideas• inspired by the “lean” methodology of leanTAP• set of clauses, each one implementing a sequent rule or an
axiom of LSE• proof search provided for free by DFS of Prolog• predicateterminating_proof_search(Gamma,Delta,Derivation).• when it fails PRONOM executes the predicatebuild_saturate_branch(Gamma,Delta,Model).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 18 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
PRONOM
Clause for axiomterminating_proof_search(Neigh,Gamma,Delta,tree(axiom),_,_,_):-
member([X,A],Gamma),member([X,A],Delta),!.
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 19 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
PRONOM
Clause for R2terminating_proof_search(Neigh,Gamma,Delta,
tree(rbox,LeftTree,RightTree),RBox,RExist,LAll):-member([X,box A],Delta),member([X,SpOfX],Neigh),member(T,SpOfX),\+member([X,A,T],RBox),!,terminating_proof_search(Neigh,Gamma,[[forall,T,0,A]|Delta],
LeftTree,[[X,A,T]|RBox],RExist,LAll),terminating_proof_search(Neigh,[[exists,T,1,A]|Gamma],Delta,
RightTree,[[X,A,T]|RBox],RExist,LAll).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 20 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Counter-model
Basic ideas• predicate build_saturate_branch• build an open, saturated branch• clauses are the same as the predicate
terminating_proof_search, however rules introducing a branchin a backward proof search are implemented by pairs of(disjoint) clauses, each one representing an attempt to buildan open saturated branch
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 21 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
PRONOM
Clauses for R2build_saturate_branch(Neigh,Gamma,Delta,Model,RBox,RExist,LAll):-
member([X,box A],Delta),member([X,SpOfX],Neigh),member(T,SpOfX),\+member([X,A,T],RBox),build_saturate_branch(Neigh,Gamma,[[forall,T,0,A]|Delta],Model,
[[X,A,T]|RBox],RExist,LAll).build_saturate_branch(Neigh,Gamma,Delta,Model,RBox,RExist,LAll):-
member([X,box A],Delta),member([X,SpOfX],Neigh),member(T,SpOfX),\+member([X,A,T],RBox),build_saturate_branch(Neigh,[[exists,T,1,A]|Gamma],Delta,Model,
[[X,A,T]|RBox],RExist,LAll).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 22 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Web application
http://193.51.60.97:8000/pronom/
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 23 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 24 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Hypersequent Calculi HE?
Basic ideas• internal calculi• direct interpretation of a sequent into a NNML formula• easier to describe a decision procedure• block 〈Σ〉, where Σ is a multiset of formulas of L• sequent: pair Γ⇒ ∆, where Γ is a multiset of formulas and
blocks, and ∆ is a multiset of formulas
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 25 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Hypersequent Calculi HE?
Basic ideas• hypersequent S1 | ... | Sn, where S1, ...,Sn are sequents• single sequents interpreted as:
i(A1, ...,An, 〈Σ1〉, ..., 〈Σm〉 ⇒ B1, ...,Bk) =
=∧i≤n
Ai ∧∧j≤m
2∧
Σj →`≤k B`
• validity of a sequent S in a bi-neighbourhood modelMM |= S : for all w ∈M,M,w i(S)
• ifM |= S for some S ∈ H, H is valid inM• H is valid if it is valid in all models of that kind
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 26 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Hypersequent Calculi HE?
initG | p, Γ⇒ ∆, p
⊥LG | ⊥, Γ⇒ ∆
>RG | Γ⇒ ∆,>
G | A→ B, Γ⇒ ∆,A G | B,A→ B, Γ⇒ ∆→LG | A→ B, Γ⇒ ∆
G | A, Γ⇒ ∆,A→ B,B→RG | Γ⇒ ∆,A→ B
G | 〈A〉,2A, Γ⇒ ∆2L
G | 2A, Γ⇒ ∆
G | 〈Σ〉, Γ⇒ ∆,2B | Σ⇒ BM2R
G | 〈Σ〉, Γ⇒ ∆,2B
G | 〈Σ〉, Γ⇒ ∆,2B | Σ⇒ B G | 〈Σ〉, Γ⇒ ∆,2B | B V Σ2R
G | 〈Σ〉, Γ⇒ ∆,2B
G | A⇒ BV1
G | AV B
G | A⇒ B G | AV ΣV2 |Σ| ≥ 1
G | AV B,Σ
G | 〈>〉, Γ⇒ ∆N
G | Γ⇒ ∆
G | 〈Σ,Π〉, 〈Σ〉, 〈Π〉, Γ⇒ ∆C
G | 〈Σ〉, 〈Π〉, Γ⇒ ∆
Figure: Rules of HE? .Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 27 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 28 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Implementation
Basic ideas• Same ideas of PRONOM• Prolog implementation inspired by leanTAP• hypersequent represented with a Prolog list whose elements
are Prolog terms:• singleSeq(Gamma,Delta,Additional)• each one represents a sequent Γ⇒ ∆ in the hypersequent• Additional: Prolog list for termination
• Two main predicates for finding either a derivation or acountermodel
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 29 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Clause for axiomterminating_proof_search(Hyper,tree(axiom,PrintableHyper,no,no)):-
member(singleSeq([Gamma,Delta],_),Hyper),member(P,Gamma), member(P,Delta),!,extractPrintableSequents(Hyper,PrintableHyper).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 30 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Clause for 2R
terminating_proof_search(Hyper,tree(rbox,PrintableHyper,Sub1,Sub2)):-select(singleSeq([Gamma,Delta],Additional),Hyper,NewHyper),member(Sigma,Gamma),is_list(Sigma),member(box B,Delta),list_to_ord_set(Sigma,SigmaOrd),\+member(apdR(SigmaOrd,B),Additional),!,terminating_proof_search([singleSeq([Sigma,[B]],[])|[singleSeq([Gamma,Delta],[apdR(SigmaOrd,B)|Additional])|NewHyper]],Sub1),
terminating_proof_search([singleSeq([[],[B => Sigma]],[])|[singleSeq([Gamma,Delta],[apdR(SigmaOrd,B)|Additional])|NewHyper]],Sub2),
extractPrintableSequents(Hyper,PrintableHyper).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 31 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Countermodel constructionbuild_saturated_branch(Hyper,Model):-
select(singleSeq([Gamma,Delta],Additional),Hyper,NewHyper),member(Sigma,Gamma),is_list(Sigma),member(box B,Delta),list_to_ord_set(Sigma,SigmaOrd),\+member(apdR(SigmaOrd,B),Additional),build_saturated_branch([singleSeq([Sigma,[B]],[])|
[singleSeq([Gamma,Delta],[apdR(SigmaOrd,B)|Additional])|NewHyper]],Model).
build_saturated_branch(Hyper,Model):-select(singleSeq([Gamma,Delta],Additional),Hyper,NewHyper),member(Sigma,Gamma),is_list(Sigma),member(box B,Delta),list_to_ord_set(Sigma,SigmaOrd),\+member(apdR(SigmaOrd,B),Additional),build_saturated_branch([singleSeq([[],[B => Sigma]],[])|
[singleSeq([Gamma,Delta],[apdR(SigmaOrd,B)|Additional])|NewHyper]],Model).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 32 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Implementation
• Last clause:
Countermodelbuild_saturated_branch(Hyper,model(Hyper)):-\+instanceOfAnAxiom(Hyper).
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 33 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Web application
http://193.51.60.97:8000/HYPNO/
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 34 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Table of Contents1. Non-Normal Modal Logics2. Bi-neighbourhood semantics
Basic System EExtensions
3. Sequent calculi LSE∗
4. PRONOMFinding a derivationCounter-model construction
5. Hypersequent Calculi HE?
6. HYPNOFinding a derivationCounter-model construction
7. ConclusionsGian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 35 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Non-normal modal logics
Our contribution• sequent and hypesequent calculi for NNMLs• first programs providing both proof-search and countermodel
generation for the whole cube of NNML
Future Works• use of free variables for term instantiation• implement an automated transformation of bi-neighbourhood
countermodels into standard neighbourhood models
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 36 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Best student paper award
Gian Luca Pozzato
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 37 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Description Logics• Important formalisms of knowledge representation• Two key advantages:
• well-defined semantics based on first-order logic• good trade-off between expressivity and complexity
• at the base of languages for the semantic (e.g. OWL)
Knowledge bases
• Two components:
• TBox=inclusion relations among concepts (e.g.Dog v Mammal)
• ABox= instances of concepts and roles = properties andrelations among individuals (e.g. Dog(saki))
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 38 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Description Logics• Important formalisms of knowledge representation• Two key advantages:
• well-defined semantics based on first-order logic• good trade-off between expressivity and complexity
• at the base of languages for the semantic (e.g. OWL)
Knowledge bases• Two components:
• TBox=inclusion relations among concepts (e.g.Dog v Mammal)
• ABox= instances of concepts and roles = properties andrelations among individuals (e.g. Dog(saki))
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 38 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Description Logics• Important formalisms of knowledge representation• Two key advantages:
• well-defined semantics based on first-order logic• good trade-off between expressivity and complexity
• at the base of languages for the semantic (e.g. OWL)
Knowledge bases• Two components:
• TBox=inclusion relations among concepts (e.g.Dog v Mammal)
• ABox= instances of concepts and roles = properties andrelations among individuals (e.g. Dog(saki))
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 38 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Description Logics• Important formalisms of knowledge representation• Two key advantages:
• well-defined semantics based on first-order logic• good trade-off between expressivity and complexity
• at the base of languages for the semantic (e.g. OWL)
Knowledge bases• Two components:
• TBox=inclusion relations among concepts (e.g.Dog v Mammal)
• ABox= instances of concepts and roles = properties andrelations among individuals (e.g. Dog(saki))
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 38 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
DLs with nonmonotonic features• need of representing prototypical properties and of reasoning
about defeasible inheritance• handle defeasible inheritance needs the integration of some
kind of nonmonotonic reasoning mechanism• DLs + MKNF• DLs + circumscription• DLs + default
• all these methods present some difficulties ...
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 39 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
DLs with typicality• Non-monotonic extensions of Description Logics for reasoning
about prototypical properties and inheritance with exceptions• Basic idea: to extend DLs with a typicality operator T• T (C ) singles out the “most normal” instances of the concept C
• semantics of T defined by a set of postulates that are arestatement of Lehmann-Magidor axioms of rational logic
Basic notions• A KB comprises assertions T (C) v D
• T (Dog) v Affectionate means “normally, dogs are affectionate”
• T is nonmonotonic
• C v D does not imply T (C ) v T (D)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 40 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
DLs with typicality• Non-monotonic extensions of Description Logics for reasoning
about prototypical properties and inheritance with exceptions• Basic idea: to extend DLs with a typicality operator T• T (C ) singles out the “most normal” instances of the concept C• semantics of T defined by a set of postulates that are a
restatement of Lehmann-Magidor axioms of rational logic
Basic notions• A KB comprises assertions T (C) v D
• T (Dog) v Affectionate means “normally, dogs are affectionate”
• T is nonmonotonic
• C v D does not imply T (C ) v T (D)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 40 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
ExampleT (Pig) v ¬FireBreathingT (Pig u Pokemon) v FireBreathing
Reasoning
• ABox:
• Pig(tepig)
• Expected conclusions:
• ¬FireBreathing(tepig)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 41 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
ExampleT (Pig) v ¬FireBreathingT (Pig u Pokemon) v FireBreathing
Reasoning• ABox:
• Pig(tepig)
• Expected conclusions:
• ¬FireBreathing(tepig)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 41 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
ExampleT (Pig) v ¬FireBreathingT (Pig u Pokemon) v FireBreathing
Reasoning• ABox:
• Pig(tepig)
• Expected conclusions:• ¬FireBreathing(tepig)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 41 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
ExampleT (Pig) v ¬FireBreathingT (Pig t Pokemon) v FireBreathing
Reasoning• ABox:
• Pig(tepig),Pokemon(tepig)
• Expected conclusions:• FireBreathing(tepig)
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 42 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Semantics• = 〈∆I , <, .I 〉
• additional ingredient: preference relation among domainelements
• < is an irreflexive, transitive, modular and well-foundedrelation over ∆:• for all S ⊆ ∆I , for all x ∈ S , either x ∈ Min<(S) or∃y ∈ Min<(S) such that y < x
• Min<(S) = {u : u ∈ S and @z ∈ S s.t. z < u}• Semantics of the T operator: (T (C ))I = Min<(C I )
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 43 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Rational closure• Preference relation among models of a KB
• M1 < M2 if M1 contains less exceptional (not minimal)elements
• M minimal model of KB if there is no M ′ model of KB suchthat M ′ < M
• Minimal entailment
• KB |=min F if F holds in all minimal models of KB
• Nonmonotonic logic
• KB |=min F does not imply KB’ |=min F with KB’ ⊃ KB
• Corresponds to a notion of rational closure of KB
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 44 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Rational closure• Preference relation among models of a KB
• M1 < M2 if M1 contains less exceptional (not minimal)elements
• M minimal model of KB if there is no M ′ model of KB suchthat M ′ < M
• Minimal entailment
• KB |=min F if F holds in all minimal models of KB
• Nonmonotonic logic
• KB |=min F does not imply KB’ |=min F with KB’ ⊃ KB
• Corresponds to a notion of rational closure of KB
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 44 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Rational closure• Preference relation among models of a KB
• M1 < M2 if M1 contains less exceptional (not minimal)elements
• M minimal model of KB if there is no M ′ model of KB suchthat M ′ < M
• Minimal entailment
• KB |=min F if F holds in all minimal models of KB• Nonmonotonic logic
• KB |=min F does not imply KB’ |=min F with KB’ ⊃ KB• Corresponds to a notion of rational closure of KB
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 44 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Probabilities for Concept combination• Further extension: p :: T (C ) v D
• p ∈ (0.5, 1) degree of belief• prototype of concepts CH and CM
• distributed semantics• selection of typicality inclusion to be considered as true V
different scenarios• probability distribution over scenarios
• DISPONTE semantics + heuristics from cognitive semanticsfor concept combination• Prototype of the combined concept CH u CM
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 45 / 46
Non-Normal Modal LogicsBi-neighbourhood semantics
Sequent calculi LSE∗PRONOM
Hypersequent Calculi HE?
HYPNOConclusions
Universitá degli Studi di Torino
Description Logics
Application to RaiPlay (with Centro Ricerche RAI)• Recommender system for RaiPlay• New genres obtained by combining basic ones• Glass box approach• Prototypes from data
Gian Luca POZZATO 13 febbraio 2020 Proof theory for NNMLs 46 / 46