Modality

Local identifier: xwkont:concept:modality Slug: modality Editorial status: reviewed Created: 2026-07-07 Modified: 2026-07-07

Scope Note

This crosswalk compares how the source ontologies represent modal qualification: necessity, possibility, conditionality, and volitional/non-volitional framing when those are attached to a process, state of affairs, proposition, or related bearer.

GUM is the only source here that reifies that space as a dedicated quality branch, ModalQuality, paired with a dedicated ascription relation, ModalPropertyAscription. SUMO also reifies modality, but at a different level: an alethic attribute layer on propositions (AlethicAttribute with modalAttribute, plus Possibility and Necessity). TUpper provides an explicit possibility predicate (poss). UFO uses modal logic substantively — a dedicated first-order modal-logic formalization section for its own axioms, plus a "modally fragile" characterization of perdurants/events — but does not introduce a dedicated modality-of-the-subject-matter class in the ontology vocabulary itself, the way GUM and SUMO do. BFO, DOLCE, GFO, and YAMATO yielded only incidental uses of "possible" / "necessary" in comments or prose, independently re-verified directly against their primary artifacts.

This draft does not re-derive quality.md's SimpleQuality finding (xwkont:correspondence:quality:007, xwkont:mapping:quality:012) and does not re-map disposition-capacity.md's GeneralPossibility / Ability findings (xwkont:correspondence:disposition-capacity:005-006, xwkont:mapping:disposition-capacity:003-004).

Labels, Alternate Labels, and Source Terminology

Role	Label or term	Source	Language	Notes
XwkOnt working label	Modality	XwkOnt	en	Working label for modal qualification as a source-side construct.
Source term	(no dedicated modality class/operator found)	BFO	en	Full-text search of bfo-core.ttl returned no modal hits.
Source term	(no dedicated modality class/operator found)	DOLCE	en	Only incidental lexical uses of "possible" / "necessary" were found.
Source term	Formal semantics in a modal logic	UFO	en	Modal operators (necessity, possibility) appear in the paper's own Section 3 formalization of UFO's axioms, not as a dedicated ontology class over the subject matter.
Source term	AlethicAttribute / modalAttribute / Possibility / Necessity	SUMO	en	Explicit alethic modal layer; SUMO also has deontic and subjective-assessment siblings.
Source term	(no dedicated modality class/operator found)	GFO	en	Only necessary / necessary_for surfaced in the checked base module.
Source term	(no dedicated modality class/operator found)	YAMATO	en	Only ordinary English uses of "necessary" / "possible" were found.
Source term	poss	TUpper	en	Explicit possibility predicate over activity/occurrence structure.
Source term	ModalQuality / Conditional / NonConditional / NonVolitional / Volitional / Necessity / Possibility / ModalPropertyAscription	GUM	en	The dedicated modal-quality branch and its ascription relation.

Source Definitions and Contextual Notes

Source	Term or identifier	Dimension	Claim type	Definition, quotation, or paraphrase	Reference	Locator	Notes
BFO	(no dedicated modality class or operator)	technical	editorial observation	Full-text search of bfo-core.ttl returned no hits for modal, modality, necessity, possibility, necessary, possible, deontic, or alethic.	xwkont:ref:bfo-2020	verified absence: bfo-core.ttl, searched directly 2026-07-07	No modality branch was found.
DOLCE	(no dedicated modality class or operator)	technical	editorial observation	The checked base file uses ordinary language only, e.g. "possibilia" and "as large as possible," and one unrelated comment mentions a "necessary axiom of compresence." No modal class/operator was found.	xwkont:ref:dolce-lite-owl	verified absence: DOLCE-Lite.owl, searched directly 2026-07-07	Lexical hits only, not a reified modality layer.
UFO	Formal semantics in a modal logic	both	direct quotation	The paper names "a formal semantics in a sortal quantified modal logic" among UFO's constituent theories, and Section 3 ("The formalization of UFO in First-Order Modal Logic") states: "the first-order modal logic QS5 plus the Barcan formula and its converse suffices... The modal operators of necessity (2) and possibility (3) are used with their usual meaning." Perdurants/events are separately characterized as "modally fragile... there is no cross-world identity between them."	xwkont:ref:ufo-2021	verified: full paper text, checked against a complete extraction dated 2026-07-06 (a day before this session; today's own DOI/mirror fetch attempts returned HTTP 403, so this session reused that extraction rather than a fresh fetch)	This is formalization/theory machinery (a modal logic used to state UFO's own axioms), not a dedicated modality-of-the-subject-matter class the way GUM's ModalQuality or SUMO's AlethicAttribute are.
SUMO	AlethicAttribute / modalAttribute / Possibility / Necessity	technical	paraphrase	SUMO reifies an alethic modal layer: AlethicAttribute is the class of attributes relating to possibility and necessity; Possibility and Necessity are instances of it; modalAttribute carries the normative force of a proposition. SUMO also has a separate deontic branch under NormativeAttribute.	xwkont:ref:sumo-niles-pease-2001	verified: Merge.kif, searched directly 2026-07-07	This is the clearest explicit modal reification outside GUM.
GFO	(no dedicated modality class or operator)	technical	editorial observation	The only hits were necessary inside the Material_persistant definition and the property name necessary_for; both are relational or ordinary uses, not a modal branch.	xwkont:ref:gfo	verified absence: gfo-base.owl, searched directly 2026-07-07	No modality class/operator was found.
YAMATO	(no dedicated modality class or operator)	philosophical	editorial observation	The report uses "necessary" and "possible" in ordinary prose, e.g. the ontology premise being "necessary" and some quantity descriptions having "possible values," but it does not define a modal class or operator.	xwkont:ref:yamato-mizoguchi-2010	verified absence: YAMATO101216.txt, searched directly 2026-07-07	Incidental lexical hits only.
TUpper	poss	technical	direct quotation	poss is an explicit predicate: an activity "can possibly occur" after an occurrence. Other possible hits are ordinary prose in beginof, endof, and precedes.	xwkont:ref:tupper-colore	verified: TUpper-Terms.html, searched directly 2026-07-07	Operator-level modality, not a reified class.
GUM	ModalQuality	technical	direct quotation	"being able" to do something; rdfs:subClassOf SimpleQuality. This is the root of GUM's modal branch.	xwkont:ref:gum-owl	verified: GUM-31.owl, class ModalQuality, fetched and read directly 2026-07-07	The superclass SimpleQuality is already covered in quality.md; this row only uses it as inherited context.
GUM	Conditional	technical	direct quotation	"would, might, could"	xwkont:ref:gum-owl	verified: GUM-31.owl, class Conditional, fetched and read directly 2026-07-07	rdfs:subClassOf ModalQuality; owl:disjointWith NonConditional, NonVolitional, Volitional.
GUM	NonConditional	technical	direct quotation	"will, must, can"	xwkont:ref:gum-owl	verified: GUM-31.owl, class NonConditional, fetched and read directly 2026-07-07	rdfs:subClassOf ModalQuality; owl:disjointWith NonVolitional, Volitional.
GUM	NonVolitional	technical	direct quotation	"did not take" direct responsibility for the process	xwkont:ref:gum-owl	verified: GUM-31.owl, class NonVolitional, fetched and read directly 2026-07-07	rdfs:subClassOf ModalQuality; owl:disjointWith Volitional.
GUM	Volitional	technical	direct quotation	"active decision" or volition in performing a process	xwkont:ref:gum-owl	verified: GUM-31.owl, class Volitional, fetched and read directly 2026-07-07	rdfs:subClassOf ModalQuality; no explicit owl:disjointWith in the class block itself.
GUM	Necessity	technical	direct quotation	"must, should" / "necessary" / "required"	xwkont:ref:gum-owl	verified: GUM-31.owl, class Necessity, fetched and read directly 2026-07-07	rdfs:subClassOf NonVolitional; owl:disjointWith Possibility.
GUM	Possibility	technical	direct quotation	"general modal quality"	xwkont:ref:gum-owl	verified: GUM-31.owl, class Possibility, fetched and read directly 2026-07-07	rdfs:subClassOf NonVolitional; no explicit owl:disjointWith in the class block itself.
GUM	ModalPropertyAscription	technical	direct quotation	"ascription of a modal quality"	xwkont:ref:gum-owl	verified: GUM-31.owl, class ModalPropertyAscription, fetched and read directly 2026-07-07	rdfs:subClassOf PropertyAscription; attribute allValuesFrom ModalQuality; owl:disjointWith ProvenancePropertyAscription, ScaledComparison, SizePropertyAscription, and UsePropertyAscription (declared on this class's own block), plus LogicalPropertyAscription (declared reciprocally on that class's own block — corrected during review, see uncertainty-005). Five disjoint classes total, not four.

Source Ontology Correspondences

Correspondence ID	Source ontology	Source term	Source identifier or IRI	Source version	Reference	Inclusion rationale
xwkont:correspondence:modality:001	BFO	(no dedicated modality class/operator found)	not applicable	BFO 2020	xwkont:ref:bfo-2020	No modal branch or operator was found in the checked core file.
xwkont:correspondence:modality:002	DOLCE	(no dedicated modality class/operator found)	not applicable	DOLCE-Lite v397	xwkont:ref:dolce-lite-owl	Only incidental lexical hits; no modal branch was found.
xwkont:correspondence:modality:003	UFO	formal semantics in modal logic	not applicable	Applied Ontology, 2021	xwkont:ref:ufo-2021	Kept because the paper explicitly names and uses first-order modal logic (QS5 plus Barcan formula) to formalize UFO's own axioms in Section 3, and separately characterizes perdurants/events as "modally fragile" — but this is formalization/theory machinery, not a source ontology class or operator analogous to GUM's ModalQuality branch or SUMO's AlethicAttribute.
xwkont:correspondence:modality:004	SUMO	AlethicAttribute / modalAttribute / Possibility / Necessity	AlethicAttribute, modalAttribute, Possibility, Necessity	current Merge.kif	xwkont:ref:sumo-niles-pease-2001	Explicit alethic modal layer; the clearest non-GUM modal reification in the checked sources.
xwkont:correspondence:modality:005	GFO	(no dedicated modality class/operator found)	not applicable	GFO 2024-11-18	xwkont:ref:gfo	Only incidental lexical hits (necessary, necessary_for) were found.
xwkont:correspondence:modality:006	YAMATO	(no dedicated modality class/operator found)	not applicable	2010-12-16 report	xwkont:ref:yamato-mizoguchi-2010	Only ordinary prose uses of possible / necessary were found.
xwkont:correspondence:modality:007	TUpper	poss	poss	TUpper COLORE formalization	xwkont:ref:tupper-colore	Explicit possibility predicate over activity-occurrence structure.
xwkont:correspondence:modality:008	GUM	ModalQuality / Conditional / NonConditional / NonVolitional / Volitional / Necessity / Possibility / ModalPropertyAscription	http://www.ontospace.uni-bremen.de/ontology/stable/GUM-3.owl#ModalQuality, #Conditional, #NonConditional, #NonVolitional, #Volitional, #Necessity, #Possibility, #ModalPropertyAscription	GUM 3.1	xwkont:ref:gum-owl	Dedicated modal-quality branch plus its ascription relation; this is the source-side anchor for the crosswalk.

Semantic Comparison Notes

Note ID	Dimension	Claim type	Note	Supporting references	Confidence
note-001	technical	editorial observation	GUM and SUMO are both explicit about modality, but they model it at different levels: GUM treats modal qualification as a quality of a process and a dedicated ascription relation; SUMO treats it as an alethic attribute of propositions plus a predicate that assigns the attribute. That makes ModalQuality and AlethicAttribute comparable, but not interchangeable.	xwkont:ref:gum-owl, xwkont:ref:sumo-niles-pease-2001	high
note-002	technical	editorial observation	GUM's modal branch is two-tiered: Conditional / NonConditional / NonVolitional / Volitional are direct children of ModalQuality, while Necessity and Possibility sit one level lower under NonVolitional. That is structurally different from a flat "possible/necessary" pair and should not be flattened in comparison.	xwkont:ref:gum-owl	high
note-003	technical	editorial observation	TUpper's poss is an operator-level possibility predicate over activity and occurrence structure. It is closer to a process-trajectory constraint than to a bearer-side quality, so it is relevant to this crosswalk but not a direct class-level match to GUM's ModalQuality.	xwkont:ref:tupper-colore	high
note-004	both	editorial observation	UFO does use modal vocabulary substantively, not just incidentally: Section 3 of the paper is a first-order modal-logic formalization of UFO's own axioms (QS5 plus the Barcan formula, explicit necessity/possibility operators), and the paper separately uses "modally fragile" to characterize perdurants/events. That vocabulary sits inside the paper's formalization and theory narrative, though — the checked UFO source does not introduce a dedicated modality-of-the-subject-matter class or operator analogous to GUM's branch or SUMO's AlethicAttribute/modalAttribute.	xwkont:ref:ufo-2021	high
note-005	technical	editorial observation	BFO, DOLCE, GFO, and YAMATO did not yield a dedicated modality branch in the checked artifacts. Their hits were lexical only: ordinary "possible"/"necessary" wording in comments or prose, not a reified modal category.	xwkont:ref:bfo-2020, xwkont:ref:dolce-lite-owl, xwkont:ref:gfo, xwkont:ref:yamato-mizoguchi-2010	high
note-006	philosophical	editorial observation	GUM is the only source here that explicitly combines modal qualification with volitional framing in the same branch. The source's Conditional / NonConditional split sits beside NonVolitional / Volitional, which makes the modal family both semantically richer and more linguistically motivated than the other sources' modal machinery.	xwkont:ref:gum-owl	high

Mapping Assertions or Candidate Relations

Mapping ID	Subject	Relation category	Object	predicate_id	mapping_justification	Status	Confidence	Rationale	Provenance
xwkont:mapping:modality:001	GUM:ModalQuality	related	SUMO:AlethicAttribute	skos:relatedMatch	semapv:ManualMappingCuration	candidate	medium-high	Both are explicit modal branches, but GUM models modality as a quality of processes while SUMO models it as an attribute of propositions. Same general semantic territory, different formal level.	xwkont:ref:gum-owl, xwkont:ref:sumo-niles-pease-2001
xwkont:mapping:modality:002	GUM:ModalPropertyAscription	related	SUMO:modalAttribute	skos:relatedMatch	semapv:ManualMappingCuration	candidate	medium	Both are ascription mechanisms attaching modal force to a bearer, but one is a class of property-ascription relations and the other is a binary predicate. Related, not equivalent.	xwkont:ref:gum-owl, xwkont:ref:sumo-niles-pease-2001
xwkont:mapping:modality:003	GUM:Possibility	explicit-non-equivalence	SUMO:Possibility	none	semapv:ManualMappingCuration	candidate	high	Same lexical label, different formal kind and bearer level: GUM's Possibility is a process-quality class; SUMO's Possibility is an AlethicAttribute instance applying to propositions. Equivalence should not be asserted.	xwkont:ref:gum-owl, xwkont:ref:sumo-niles-pease-2001
xwkont:mapping:modality:004	GUM:Necessity	explicit-non-equivalence	SUMO:Necessity	none	semapv:ManualMappingCuration	candidate	high	Same reason as mapping-003: same lexical label, different ontological kind and level.	xwkont:ref:gum-owl, xwkont:ref:sumo-niles-pease-2001
xwkont:mapping:modality:005	GUM:Possibility	related	TUpper:poss	skos:relatedMatch	semapv:ManualMappingCuration	candidate	low-medium	Both encode possibility, but TUpper does so as a predicate over activity/occurrence structure, not as a quality class. The semantic overlap is real, but the formal kind differs.	xwkont:ref:gum-owl, xwkont:ref:tupper-colore

Uncertainty, Non-Equivalence, and Open Questions

Item ID	Type	Description	Impact	Follow-up
uncertainty-001	open-question	SUMO's modal layer is explicit, but it is propositional and alethic rather than process-quality based. That makes mapping-001 and mapping-002 intentionally conservative.	Prevents a false equivalence between two real modal formalisms.	Keep related unless a maintainer wants a stricter "same semantic field, different level" policy.
uncertainty-002	non-equivalence	GUM:Possibility / GUM:Necessity are classes, while SUMO's Possibility / Necessity are instances of AlethicAttribute. The same lexical labels are not enough to collapse that difference.	Keeps mapping-003 / mapping-004 out of exact-equivalence-candidate.	None unless the source-side modeling changes.
uncertainty-003	open-question	UFO's modal logic is theoretically relevant and substantively documented (Section 3's formalization, plus the "modally fragile" event characterization), but it is formalization/theory machinery, not a source-term correspondence in the same sense as GUM's ModalQuality or SUMO's AlethicAttribute. Separately: this session's own live fetch attempts (DOI 10.3233/AO-210256, SageJournals, philpapers.org's Semantic-Scholar-indexed mirror) all returned HTTP 403, the same recurring block continuous-discrete.md's and list-sequence.md's reviews hit for this exact paper earlier the same week — this row's verification relies on a complete extraction from a day earlier (2026-07-06), not a fresh fetch today, so the finding is grounded but the access problem itself is ongoing.	Keeps UFO out of a misleading class-level mapping while still recording its real modal-formalization content.	Revisit only if a later UFO artifact introduces a dedicated modality-of-the-subject-matter class or operator; separately, the DOI/mirror access block should be rechecked next time this paper is needed, per the recurring problem already logged in list-sequence.yaml, change.yaml, and continuous-discrete.yaml.
uncertainty-004	open-question	TUpper's poss is the only explicit modal predicate found in that source. It is close enough to keep in the draft, but not close enough to claim equivalence to GUM's process-quality branch.	Supports related, not close-match.	Revisit only if a deeper PSL module adds a stronger modal class or if the maintainer wants a stricter operator-level comparison.
uncertainty-005	resolved	Corrected during Claude's independent review pass (2026-07-07): PropertyAscription (the shared superclass) itself is owl:disjointWith only QuantityAscription — it does not disjoin ModalPropertyAscription from its sibling *PropertyAscription classes, and no such disjointness is inherited. The real additional disjointness is declared reciprocally on LogicalPropertyAscription's own class block (owl:disjointWith ModalPropertyAscription, alongside MaterialPropertyAscription, ProvenancePropertyAscription, ScaledComparison), not on ModalPropertyAscription's own block or on the superclass. So ModalPropertyAscription is owl:disjointWith five classes total, not four: ProvenancePropertyAscription, ScaledComparison, SizePropertyAscription, UsePropertyAscription (declared on its own block) plus LogicalPropertyAscription (declared reciprocally on that class's block).	Row 51 in Source Definitions understated the disjointness by one class; corrected there.	None — resolved by direct verification against GUM-31.owl.

Provenance and References

• xwkont:ref:bfo-2020 — Basic Formal Ontology (BFO) 2020 — verified absence directly against bfo-core.ttl, 2026-07-07
• xwkont:ref:dolce-lite-owl — DOLCE-Lite OWL translation — verified absence directly against DOLCE-Lite.owl, 2026-07-07
• xwkont:ref:ufo-2021 — UFO: Unified Foundational Ontology — verified directly against a complete paper-text extraction dated 2026-07-06 (this session's own DOI/mirror fetch attempts, 2026-07-07, returned HTTP 403, the same recurring block continuous-discrete.md/list-sequence.md hit; the extraction predates that block by one day and was reused rather than re-fetched)
• xwkont:ref:sumo-niles-pease-2001 — Towards a Standard Upper Ontology — verified directly against Merge.kif, 2026-07-07
• xwkont:ref:gfo — General Formal Ontology (GFO) — verified absence directly against gfo-base.owl, 2026-07-07
• xwkont:ref:yamato-mizoguchi-2010 — YAMATO: Yet Another More Advanced Top-level Ontology — verified absence directly against YAMATO101216.txt, 2026-07-07
• xwkont:ref:tupper-colore — TUpper COLORE formalization — verified directly against TUpper-Terms.html, 2026-07-07
• xwkont:ref:gum-owl — GUM 3.1 OWL — verified directly against GUM-31.owl, 2026-07-07

Review History

Review ID	Date	Outcome	Notes
—	2026-07-07	Draft created	Codex (GPT-5.4-Mini, Extra-High) verified GUM's modal branch directly, separated SUMO/TUpper/UFO from incidental lexical hits in the other sources, and kept quality.md / disposition-capacity.md findings cited rather than re-derived.
—	2026-07-07	Independent review pass (Claude), passed — advanced draft → reviewed	Re-fetched and re-checked all 8 sources' primary artifacts directly. The UFO row's two direct quotations were initially flagged as a possible repeat of the continuous-discrete.md/list-sequence.md HTTP-403-access-block pattern (today's own live DOI/mirror fetch attempts did return HTTP 403, confirmed directly), but both quotations were then located and confirmed verbatim in a complete paper-text extraction dated one day earlier (2026-07-06, from a different session's still-present scratchpad) — so the content is genuinely grounded, not fabricated, though it relies on that slightly-earlier extraction rather than a fresh fetch this session; the draft's locator note was corrected to say so explicitly rather than implying a same-day fetch. One real defect was found and corrected: uncertainty-005 incorrectly stated that GUM's PropertyAscription superclass disjoins ModalPropertyAscription from its sibling ascription classes — direct inspection of GUM-31.owl found PropertyAscription disjoins only QuantityAscription, and the real additional disjointness (LogicalPropertyAscription) is declared reciprocally on that sibling class's own block, not inherited from the superclass; corrected in both uncertainty-005 and the Source Definitions row for ModalPropertyAscription (five disjoint classes, not four). BFO, DOLCE, GFO, YAMATO, SUMO, TUpper, and all eight GUM class definitions were independently re-fetched and re-verified with no other discrepancies found. Advanced to reviewed: this candidate's sole source (GUM) is directly verified, consistent with continuous-discrete.md's single-source precedent and every other GUM-sourced reviewed crosswalk in this repository, notwithstanding GUM's own base/core module structure remaining an open, project-wide, previously-unresolved question (xwkont:ref:gum-owl's Citation and Locator Notes) not specific to this crosswalk.

Future Work

• Decide whether mapping-001 / mapping-002 should stay related or be tightened to a different category after maintainer review.
• If a future source introduces a process-level modal class or a proposition-level modal class, compare it first against GUM's ModalQuality / ModalPropertyAscription and SUMO's AlethicAttribute / modalAttribute.
• If this draft is exported later, preserve ModalPropertyAscription's full five-class owl:disjointWith set (four declared on its own block, one — LogicalPropertyAscription — declared reciprocally on that sibling's block) rather than flattening or under-counting it.
• This session's own live DOI/mirror fetch attempts for the UFO paper returned HTTP 403 (the same recurring block hit by continuous-discrete.md/list-sequence.md); this crosswalk's UFO content is grounded in a complete extraction from one day earlier (2026-07-06), not a fresh fetch. A future pass with live access should confirm no additional modal vocabulary was missed by that extraction.