Introduction to Ontologies

Permission to reuse granted so long as this notice is not altered – Author: Adam Pease [email protected], 2003

Introduction to Ontologies

• Introduction – 5 min• Motivation – 5 min• Ontologies compared to other stuff – 5 min• Exercise – first part – 15 min• Upper ontology specifics – 15 min• Exercise – second part – 15 min• Discussion – 15 min

Adam [email protected]

http://ontology.teknowledge.com


Ground Rules

• Increasing interactivity as presentation goes on

• Discussion about philosophy, but not Philosophy

– Practical goal of providing basic grounding in knowledge engineering

– There are many alternatives, to make progress requires making choices and getting to work

• No such thing as a dumb question


Definitions

• An ontology is a shared conceptualization of a domain

• An ontology is a set of definitions in a formal language for terms describing the world


Motivation

• select EMPDAT from PERSTAB where POS=“mgmnt”

– What does it mean?– PERSTAB is a table which lists employee data

» What’s an employee? How is an employee different from a contractor? What if I want data on both?

• Even if this information is available in English, a human has to read it


Motivation (2)

• "Parenthood is a more general relationship than motherhood."

• "Mary is the mother of Bill."

• "Who are Bill's parents?“• "Mary is the parent of Bill.”

– that fact is not stated anywhere, but can be derived by a DAML application.

Example from “Why Use DAML?” <http://www.daml.org/2002/04/why.html>


Motivation (2) continued

• More formally stated, given the statements

(motherOf subProperty parentOf)(Mary motherOf Bill)

• when stated in DAML, allows you to conclude

(Mary parentOf Bill)

• Java code or a stored procedure could do this sort of inference for facts in XML or SQL

• But the DAML spec itself says the conclusion is true• In contrast, different Java code could reach a different

conclusion


Motivation (2) continued

• (Mary motherOf Bill)• (parentOf inverse childOf)• (Bill childOf ?X)

• ?X = Mary

• The semantics of inverse is part of the DAML spec


Language Formality and Expressiveness

Formality

Exp

ress

iven

ess

Human Language

KIFCycL

OWLF-Logic

DAML

XML

SQL

HumanConsumption

MachineProcessing

MachineInference


Content Formality and Size

Formality

WordNet

Cyc

SUMO

DOLCE

Lexicons Formal Ontology

Taxonomy

Siz

e

SUMO+domain

UMLSYahoo!


Everything is not a Nail

• Ontology is not always the right tool for the job

• Face recognition, vehicle control systems etc – not the right applications for ontology


Many Ways to Use Ontology

• As an information engineering tool– Create a database schema– Map the schema to an upper ontology– Use the ontology as a set of reminders for additional

information that should be included

• As more formal comments– Define an ontology that is used to create a DB or OO

system– Use a theorem prover at design time to check for

inconsistencies

• For taxonomic reasoning– Do limited run-time inference in Prolog, a description

logic, or even Java

• For first order logical inference– Full-blown use of all the axioms at run time


Upper Ontology

• An attempt to capture the most general and reusable terms and definitions


Motivation

• Ontologies may have different names for the same things

– type – a relation between a class and an instance– instance – a relation between a class and an instance– isa – a relation between a class and an instance– …

• Ontologies may have the same name for different things, and no corresponding terms

– before – a relation between two time points– before – a relation between two time intervals

• Either use the same upper ontology, or at least map to a common upper ontology


Formal Upper Ontologies

• DOLCE• Cyc• SUMO


Simple Methodology

• Extract nouns and verbs from a source text• Find classes in SUMO for the nouns and verbs• Record a mapping as being either equal, subsuming or instance.

– type a single word that relates to the UBL term in the "SUMO term" or "English Word" text areas in the SUMO browser

• Create a subclass of SUMO if it's a subsuming mapping• Add properties to the subclass

– reusing SUMO properties– extending SUMO properties by creating a &%subrelation of an existing property

• Add English definition to the class – define constraints that express how the subclass is more specific than the

superclass

• Express the classes and properties in KIF and begin creating axioms, based on the English definitions created previously


Exercise

• Walk through the process of creating some ontology content from a source text

• Learn a general methodology• Get practical familiarity with KIF and SUMO


First Exercise (1)

• “Seven Turkish nationals of Chechen origin hijacked a Russia-bound Panamanian ferry in Trabzon. The hijackers initially threatened to kill all Russians on board unless Chechen separatists being held in Dagestan, Russia, were released. On 19 January 1998, the hijackers surrendered to Turkish authorities outside the entrance to the Bosporus. The passengers were unharmed.“

• Identify items that need formalization – start with nouns and verbs


First Exercise (2)

• “Seven Turkish nationals of Chechen origin hijacked a Russia-bound Panamanian ferry in Trabzon. The hijackers initially threatened to kill all Russians on board unless Chechen separatists being held in Dagestan, Russia, were released. On 19 January 1998, the hijackers surrendered to Turkish authorities outside the entrance to the Bosporus. The passengers were unharmed.“

• Now create terms that correspond to the nouns and verbs

• Remove redundancy• Are there any “background” notions that are not

explicit in the text?


First Exercise (3)

• Seven Turkish nationals of Chechen origin hijacked a Russia-bound Panamanian ferry in Trabzon. The hijackers initially threatened to kill all Russians on board unless Chechen separatists being held in Dagestan, Russia, were released. On 19 January 1998, the hijackers surrendered to Turkish authorities outside the entrance to the Bosporus. The passengers were unharmed

• Turkey, Chechnya, Nationality, Hijacking, Threatening, Killing, Releasing, Holding, Dagestan, Russia, Separatist, Entrance, Bosporus, Unharmed, Panama, Trabzon, Authority, Outside, boundFor, Ferry, onBoard


SUMO Overview

• Understanding what’s in the upper ontology, in order to use it effectively


High Level Distinctions

The first fundamental distinction is that between ‘Physical’ (things which have a position in space/time) and ‘Abstract’ (things which don’t)

Physical Abstract


High Level Distinctions

Partition of ‘Physical’ into ‘Objects’ and ‘Processes’

Physical

Object Process


Objects

Object

SelfConnectedObject

Substance

CorpuscularObject

Region

Collection


Processes

DualObjectProcess Substituting Transaction Comparing Attaching Detaching Combining SeparatingInternalChange BiologicalProcess QuantityChange Damaging ChemicalProcess SurfaceChange Creation StateChangeShapeChange

IntentionalProcess IntentionalPsychologicalProcess RecreationOrExercise OrganizationalProcess Guiding Keeping Maintaining Repairing Poking ContentDevelopment Making Searching SocialInteraction ManeuverMotion BodyMotion DirectionChange Transfer Transportation Radiating


Abstract

SetOrClass

Relation

Proposition

Quantity

Number

PhysicalQuantity

Attribute

Graph

GraphElement


A Little Bit of Logic

• Instance – GeorgeBush, Iraq, BobsRightBigToe

• Class – Human, Nation• Relation – WWI before WWII, Bill childOf Mary• => (read as “implies”) - if X then Y• and – X and Y are true• or – X or Y (or both) are true• not – not X – the opposite of the truth of X• exists ?X – there exists something about

which the following is true


A Little “Structural” Ontology

(instance GeorgeBush Human) – GeorgeBush is an instance of the class of humans

(exists (?X) (parent ?X GeorgeBush)) – there exists something of which

George Bush is the parent

(instance parent BinaryPredicate) – the relation of parent is a binary relation

(domain parent 1 Organism) – the first argument to the parent relation must be an instance of the class Organism

(domain parent 2 Organism) – similarly for the second argument


Linking to SUMO Terms

• Nation, Confining, Committing, SocialRole, TransportationDevice, Killing, Near, Injuring, citizen, (not…), (exists…)

• Terms from the exercise (may or may not be the same as SUMO terms):

– Turkey, Chechnya, Nationality, Hijacking, Threatening, Killing, Releasing, Holding, Dagestan, Russia, Separatist, Entrance, Bosporus, Unharmed, Panama, Trabzon, Authority, Outside, boundFor, Ferry, onBoard

• Use the terms in the first bullet to define the terms in the second bullet

– Use Nation to state: (instance Turkey Nation)


Formalization

(exists (?TURK …)

(and

(citizen ?TURK Turkey))

…

)


Formalization

(exists (?TURK ?FERRY …)

(and

(citizen ?TURK Turkey)

(instance ?FERRY FerryBoat)

…

)


Formalization

(exists (?TURK ?FERRY ?HIJACK)

(and

(citizen ?TURK Turkey)

(instance ?FERRY FerryBoat)

(instance ?HIJACK Hijacking)

(agent ?HIJACK ?TURK)

(patient ?HIJACK ?FERRY)

(earlier ?HIJACK

(DayFn 19

(MonthFn January

(YearFn 1998))))))

Introduction to Ontologies

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