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Evaluating Ontological Decisions with OntoClean
Chris Welty, Vassar College, USANicola Guarino, LADSEB-CNR, Italy
2
What is Ontology?
• A discipline of Philosophy– Meta-physics dates back to Artistotle– Ontology dates back to 17th century– The science of what is
• Borrowed by AI– McCarthy calls for “a list of things that exist”
• Evolution of meaning– Now refers to domain modelling, conceptual
modeling, knowledge engineering, etc.
3
What is an Ontology?
complexity
a catalog
a set of generallogical
constraintsa glossary
a set of text files a thesaurus
a collection of
taxonomies
a collection of frames
with automated reasoningwithout automated reasoning
4
OntoClean Approach
• Draw fundamental notions from Formal Ontology
• Establish a set of useful meta-properties, based on behavior wrt above notions
• Explore the way these meta-properties combine to form relevant property kinds
• Explore the taxonomic constraints imposed by these property kinds.
5
Dealing withOntological Relativism
• Deciding about the meta-properties carried by a given property…
Is up to YOU!
• But a common agreement must be achieved about the formal meaning (and practical utility) of meta-properties
6
What is a taxonomic relationship?
• Is-a, a-kind-of, specialization-of, subclass (Brachman, 1983)– “horse is a mammal”
• Helps deal with complexity• What does it mean?
� x (x) (x)
7
Ontology-driven conceptual modeling
Formal Ontological Properties/Relations
Useful Property Kinds
Ontology-Driven Modeling Principles
Minimal Top-Level Ontology
User
Conceptualization Conceptual Model
OntologyOntology
Methodology
8
Basic Philosophical Notions(taken from Formal Ontology)
• Essence
• Identity
• Unity
• Dependence
9
Essence and Rigidity
• Certain entities have essential properties.– Hammers must be hard.– John must be a person.
• Certain properties are essential to all their instances (compare being a person with being hard).
• These properties are rigid - if an entity is ever an instance of a rigid property, it must always be.
10
Formal Rigidity is rigid (+R): x (x) � (x)
– e.g. Person, Apple
is non-rigid (-R): x (x) ¬ � (x)– e.g. Red, Male
is anti-rigid (~R): x (x) ¬ � (x)– e.g. Student, Agent
11
Rigidity Constraint
+R ~R
• Why?
� x P(x) Q(x)
Q~R
P+R
O10
12
Identity and Unity
• Identity: is this my dog?
• Unity: is the collar part of my dog?
13
Identity criteria
• Classical formulation:
(x) (y) ((x,y) x = y)
• Generalization:(x,t) (y,t’) ((x,y,t,t’) x = y)
(synchronic: t = t’ ; diachronic: t ≠ t’)
• In most cases, is based on the sameness of certain characteristic features:
(x,y, t ,t’) = z ((x,z,t) (y,z,t’))
14
A Stronger Notion:Global ICs
• Local IC:
(x,t) (y,t’) ((x,y,t,t’) x = y)
• Global IC (rigid properties only):
(x,t) ((y,t’) (x,y,t,t’) x = y)
15
Identity Conditions along Taxonomies
• Adding ICs:– Polygon: same edges, same angles
• Triangle: two edges, one angle– Equilateral triangle: one edge
• Just inheriting ICs:– Person
• Student
16
Identity meta-properties
• Supplying (global) identity (+O)– Having some “own” IC that doesn’t hold for a
subsuming property
• Carrying (global) identity (+I)– Having an IC (either own or inherited)
• Not carrying (global) identity (-I)
17
Identity Disjointness Constraint
Properties with incompatible ICs are disjoint
Besides being used for recognizing sortals, ICs impose constraints on them, making their ontological nature explicit:
Examples:• sets vs. ordered sets• amounts of matter vs. assemblies
18
Unity Criteria
• An object x is a whole under iff is an equivalence relation that binds together all the parts of x, such that
P(y,x) (P(z,x) y,z))but not
y,z) x(P(y,x) P(z,x))
• P is the part-of relation can be seen as a generalized indirect connection
19
Unity Meta-Properties
• If all instances of a property are wholes under the same relationcarries unity (+U)
• When at least one instance of is not a whole, or when two instances of are wholes under different relations, does not carry unity (-U)
• When no instance of is a whole, carries anti-unity (~U)
20
Unity Disjointness Constraint
Properties with incompatible UCs are disjoint+U ~U
21
Property Dependence
• Does a property holding for x depend on something else besides x? (property dependence) – P(x) y Q(y)– y should not be a part of x
• Example: Student/Teacher, customer/vendor
22
Basic Property Kinds Table
O I R D
+ + + ± Type
- + + ± Quas -i type- + - - Mixin
- + ~ + Mat.role- + ~ - Phasedsortal- - + ± Category
- - ~ + Formalrole- - - - Attribution
23
Sortals, categories, and other properties
• Sortals (horse, triangle, amount of matter, person, student...)– Carry identity– Usually correspond to nouns– High organizational utility– Main subclasses: types and roles
• Categories (universal, particular, event, substance...)– No identity– Useful generalizations for sortals– Characterized by a set of (only necessary) formal properties– Good organizational utility
• Other non-sortals (red, big, decomposable, eatable, dependent, singular...)– No identity– Correspond to adjectives– Span across different sortals– Limited organizational utility (but high semantic value)
24
A formal ontology of properties
Property
Non-sortal-I
Role~R+D
Sortal+I
Formal Role
Attribution -R-D
Category +R
Mixin -D
Type +O
Quasi-type -O
Non-rigid-R
Rigid+R
Material roleAnti-rigid~R Phased sortal -D +L
25
The Backbone Taxonomy
Assumption: no entity without identity
• Since identity is supplied by types, every entity must instantiate a type
• The taxonomy of types spans the whole domain• Together with categories, types form the backbone
taxonomy, which represents the invariant structure of a domain (rigid properties spanning the whole domain)
26
Taxonomic Constraints
• +R ~R• -I +I• -U +U• +U ~U• -D +D
• Incompatible IC’s are disjoint
• Incompatible UC’s are disjoint
• Categories subsume everything
• Roles can’t subsume types
27
Phased Sortals
Backbone TaxonomyCategories
Top TypesTypes &Quasi-Types
FormalRoles
Material Roles
Attributions
Mixins
Non-sortals
Sortals
Idealized view of an ontology
28
An extended example
29
Dealing withOntological Relativism
• Deciding about the meta-properties carried by a given property…
Is up to YOU!
• But a common agreement must be achieved about the formal meaning (and practical utility) of meta-properties
42
Entity
Fruit
Physical objectGroup of people
Country
FoodAnimal Legal agent
Amount of matterGroup
Living being
LocationAgentRed
Red applePerson
Vertebrate
Apple
CaterpillarButterfly
Organization
Social entity
assign meta-properties
43
Remove non-rigid propertiesEntity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Agent-I-U+D~R
Apple+O+U-D+R
Fruit+O+U-D+R
Food+I-O~U+D~R
Country+L+U-D~R
Legal agent+L-U+D~R
Group of people+I-O~U-D+R
Red apple+I-O+U-D~R
Red-I-U-D-R
Vertebrate+I-O+U-D+R
Caterpillar+L+U-D~R
Butterfly+L+U-D~R
44
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• Living being can change
parts and remain the same, but amounts of matter can not (incompatible ICs)
• Living being is constituted of matter
45
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• Living being can change
parts and remain the same, but amounts of matter can not (incompatible ICs)
• Living being is constituted of matter
46
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• Physical objects can
change parts and remain the same, but amounts of matter can not (incompatible ICs)
• Physical object is constituted of matter
47
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• Physical objects can
change parts and remain the same, but amounts of matter can not (incompatible ICs)
• Physical object is constituted of matter
48
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• Meta-properties fine• Identity-check fails:
when an entity stops being an animal, it does not stop being a physical object (when an animal dies, its body remains)
• Constitution again
49
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• Meta-properties fine• Identity-check fails:
when an entity stops being an animal, it does not stop being a physical object (when an animal dies, its body remains)
• Constitution again
50
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• A group, and group of
people, can’t change parts - it becomes a different group
• A social entity can change parts - it’s more than just a group (incompatible IC)
• Constitution again
51
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze taxonomic links
• ~U can’t subsume +U• A group, and group of
people, can’t change parts - it becomes a different group
• A social entity can change parts - it’s more than just a group (incompatible IC)
• Constitution again
56
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
• ~R can’t subsume +R• Really want a type
restriction: all agents are animals or social entities.
• Subsumption is not disjunction!
57
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
• ~R can’t subsume +R• Really want a type
restriction: all agents are animals or social entities.
• Subsumption is not disjunction!
58
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
• ~R can’t subsume +R• Another disjunction: all
legal agents are countries, persons, or organizations Legal agent
+L-U+D~R
59
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
• ~R can’t subsume +R• Another disjunction: all
legal agents are countries, persons, or organizations Legal agent
+L-U+D~R
60
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
Legal agent+L-U+D~R
• ~R can’t subsume +R• Apple is not necessarily
food. A poison-apple, e.g., is still an apple.
• ~U can’t subsume +U• Caterpillars are wholes,
food is stuff.
Food+I-O~U+D~R
61
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Roles
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
Legal agent+L-U+D~R
• ~R can’t subsume +R• Apple is not necessarily
food. A poison-apple, e.g., is still an apple.
• ~U can’t subsume +U• Caterpillars are wholes,
food is stuff.
Food+I-O~U+D~R
62
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Analyze Attributions
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
Legal agent+L-U+D~R
• No violations• Attributions are
discouraged, can be confusing.
• Often better to use attribute values (i.e. Apple Color red)
Food+I-O~U+D~R
Red-I-U-D-R
Red apple+I-O+U-D~R
63
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Geographical Region
+O-U-D+R Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Lepidopteran+O+U-D+R
Agent-I-U+D~R
Legal agent+L-U+D~R
Food+I-O~U+D~R
Red-I-U-D-R
Red apple+I-O+U-D~R
64
Country+O+U-D+R
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Apple+O+U-D+R
Fruit+O+U-D+R
Group of people+I-O~U-D+R
Vertebrate+I-O+U-D+R
Geographical Region
+O-U-D+R
Lepidopteran+O+U-D+R
The backbone taxonomy
65
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Agent-I-U+D~R
Apple+O+U-D+R
Fruit+O+U-D+R
Food+I-O~U+D~R
Legal agent+L-U+D~R
Group of people+I-O~U-D+R
Red apple+I-O+U-D~R
Red-I-U-D-R
Vertebrate+I-O+U-D+R
Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Country+O+U-D+R
Geographical Region
+O-U-D+R
Lepidopteran+O+U-D+R
66
Entity
Fruit
Physical objectGroup of people
Country
FoodAnimal Legal agent
Amount of matterGroup
Living being
LocationAgentRed
Red applePerson
Vertebrate
Apple
CaterpillarButterfly
Organization
Social entity
Before
67
Entity-I-U-D+R
Physical object+O+U-D+R
Amount of matter +O~U-D+R Group
+O~U-D+R
Organization+O+U-D+R
Location+O-U-D+R
Living being+O+U-D+R
Person+O+U-D+R
Animal+O+U-D+R
Social entity-I+U-D+R
Agent-I-U+D~R
Apple+O+U-D+R
Fruit+O+U-D+R
Food+I-O~U+D~R
Legal agent+L-U+D~R
Group of people+I-O~U-D+R
Red apple+I-O+U-D~R
Red-I-U-D-R
Vertebrate+I-O+U-D+R
Caterpillar+L+U-D~R
Butterfly+L+U-D~R
Country+O+U-D+R
Geographical Region
+O-U-D+R
Lepidopteran+O+U-D+R
After
68
Use OntoClean for all your ontology cleaning needs!