- The document discusses the "quasi-equivalent concept trade-off" problem that frequently arises in ontology engineering when determining whether two similar concepts should be merged or kept separate. - It analyzes the differences between this problem and traditional ontology alignment, and proposes a framework with possible merging or separation outcomes when making decisions about related concept pairs. - An example involving the design of an ontology for lexicographic purposes demonstrates how the framework would be applied, with concepts being separated but connected through a domain-specific linking property.

1. Quasi-Equivalent Concept Trade-off
in Ontology Design:
Initial Considerations and Analyses
Vojtěch Svátek, Anna Nesterova,
and Viet Bach Nguyen
Prague University of Economics and Business
Czech Republic
Supported by IGA VŠE 56/2021
and by the NexusLinguarum COST Action
EKAW 2022 Bozen-Bolzano, September 27th 2022
23rd International Conference on
Knowledge Engineering and Knowledge Management

2. Research target
• A frequent (implicit or explicit) fine-grained problem in
ontology engineering:
• Given two apparently related informal concepts A and B, are
they the same?
• If not, are they still so similar that we can consider to
merging?
• Should I merge them or keep separate in a particular
context?
• We are unaware of a research effort to date that would
specifically zoom into this problem at the level of an
individual concept pair
• Never mind into its highlighted part, which we propose
to nick quasi-equivalent concept (QuEC) trade-off
• Every verdict (merge vs. separation) has its pros and cons
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 2

3. Looking around…
• Closest field with ample research:
ontology alignment (aka ontology matching)
• See http://ontologymatching.org/
• Differences:
• OA seeks bulk and (mostly) automated solutions
• QuEC trade-off zooms to an individual concept pair,
with central role of human ontologist
• OA aims to match pairs of pre-existing classes
• in the QuEC trade-off, at least one of the concepts
has not been formalized yet
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4. Ontology alignment vs. QuEC t’off
OA
QuEC trade-off
A
K
L
P
B
Q
?
B
A
A B
?
?
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5. B
A B
?
?
A
Two variants of the QuEC t’off
• We need to unify them to make the problem
conceptually simpler
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6. B
A B
?
A B
?
internalization of the pre-
existing concept
Two variants of the QuEC t’off
• We need to unify them to make the problem
conceptually simpler
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7. B
A B
?
A B
?
internalization of the pre-
existing concept
Two variants of the QuEC t’off
• We need to unify them to make the problem
conceptually simpler
thus, we are considering the quasi-
equivalence primarily in terms of
abstract notions within the
designer’s mental model (informal
conceptualization), merely
optionally / ex post corresponding
to formalized class/es
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8. Example: design of lemonBib
(a lexicographic ontology)
cito:Citation
a conceptual directional
link from a citing entity to
a cited entity, created by a
human performative act of
making a citation
„attestation“ of a
property of a word:
referencing an
external text in
which this property
is manifested by a
word occurrence
Does this pre-existing
entity correspond to my
conceptualization of
„attestation“?
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9. QuEC trade-off input and outcome
• Thanks to unification of variants, the main input
are always two concepts A and B as elements of the
designer’s informal conceptualization of the
domain
• One (or, exceptionally, both) of A and B may already be
formalized as a class in a formal (e.g., OWL) ontology
• The outcome is a fragment of a formal ontology O
• It may be either a merging or a separation outcome
• In our provisional formalization we distinguish 3 variants
of the merging outcome, and a single variant of the
separation one
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10. Merging outcome variants
• „Hard merging“
• A single class in O directly represents both A and B
• „Soft merging with equivalence/subsumption“
• Two classes representing A and B in O are connected via equivalence or
just subsumption
• „Soft merging with overlap“
• Two classes representing A and B in O have a common superclass
(other than ⊤ - the top concept), and are not declared as disjoint
• Note
• In the proposal, we tentatively coin the term “merging” for any
situation when the output classes are set-theoretically compatible
• One can surely argue that the latter two variants are not merging
proper – but at least the „essence“ of the class instances is alike, in
contrast to situations that we would label as „separation“ – disjoint =
different essence
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11. Separation outcome
• Two classes representing A and B are disjoint in O,
but connected with a logical or annotation axiom,
a predicate p “linking property” that expresses the
‘relatedness’ in other than set-theoretic terms
• Note
• We anticipate that the initial quasi-equivalence of A and
B warrants them being eventually somehow connected
in O, despite the „separation“ verdict!
• Linking property p may be either a generic predicate
(such as skos:closeMatch), or a domain-specific one
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12. Example: design of lemonBib
(a lexicographic ontology)
cito:Citation
a conceptual directional
link from a citing entity to
a cited entity, created by a
human performative act of
making a citation
Does this pre-existing entity
correspond to my
conceptualization of
„attestation“?
„attestation“ of a
property of a word:
referencing an
external text in
which this property
is manifested by a
word occurrence
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 12

13. Example: design of lemonBib
(a lexicographic ontology)
cito:Citation
a conceptual directional
link from a citing entity to
a cited entity, created by a
human performative act of
making a citation
The same citation serves for
different attestations if the
property differs: we can focus
on word senses, rhetorics, etc.
„attestation“ of a
property of a word:
referencing an
external text in
which this property
is manifested by a
word occurrence
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 13

14. Example: design of lemonBib
(a lexicographic ontology)
cito:Citation
a conceptual directional
link from a citing entity to
a cited entity, created by a
human performative act of
making a citation
Separation!!!
„attestation“ of a
property of a word:
referencing an
external text in
which this property
is manifested by a
word occurrence
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 14

15. Example: design of lemonBib
(a lexicographic ontology)
cito:Citation
a conceptual directional
link from a citing entity to
a cited entity, created by a
human performative act of
making a citation
lemonBib:Attestation
lemonBib:attestationCitation
rdfs:domain
rdfs:range
Non-set-theoretic predicate p
(domain-specific linking property)
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16. Our position + research direction
• The reviewers (rightfully) commented that the
paper is not truly written as a “position paper” but
as an early-phase research paper
• Here is our position articulated, to make up:
• Ontology engineering should provide more support to
fine-grained, entity-level (but unsolvable just using
formal logic...) decisions of the designers
• Each QuEC trade-off case entails such a decision…
• …and we are pondering about a possible support
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17. Preliminary + in-progress research
(outlined in our paper)
• Cataloging of factors influencing the merging vs. separation
decision (what we trade for what)
• ontology size (manageability, comprehensibility), data organization,
stakeholders’ interests, possibility to formulate axioms, …
• Qualitative analysis of occurrences of candidate generic
linking properties in existing ontologies, e.g., we find in LOV:
• cwmo:Idea rdfs:seeAlso skos:Concept (separation)
• dbo:Annotation owl:equivalentClass bibo:Note (soft-merging)
• Questionnaire survey with ontology designers, collecting
their experience with the QuEC trade-off
• Software support considerations
• hypothesis: a dialog tool mildly inspired by J. Boose’s Expertise
Transfer System (ETS), powered by text mining from thesauri and
lexica may work? Future work
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 17

18. Questions?
EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 18
Thank you for listening
23rd International Conference on
Knowledge Engineering and Knowledge Management
26-29 September 2022 - Bozen-Bolzano, Italy
Quasi-Equivalent Concept Trade-off in Ontology Design:
Initial Considerations and Analyses

19. EKAW 2022 | Bozen-Bolzano | 27 Sep 2022 19