• F12: SEMANTICS and ONTOLOGIES...© 2005-2006 The ATHENA Consortium. 1 • F12: SEMANTICS and...

© 2005-2006 The ATHENA Consortium. 1

• F12: SEMANTICS and ONTOLOGIES


A mini-lesson in semantics

How do you do semantics?How do you do, Semantics?

?

semantics


Semantics

• Semantics – ancient Greek for meaning σηµαίνω – I signal, sign, show

• Semantics has become a buzzword or even a fuzzword

• Example from a book about Eclipse:

– “We’ll use the same mechanisms to navigate semantic errors (…) that we use to navigate compile errors.”

– (failing tests) – semantic error is less precise than “failing tests”

– a fuzzword in this case

• Oxford English Dictionary: 2. a. Relating to signification or meaning. (as adjective)


Semantics and Definitions

• Standard way to communicate meaning is by definition

• definition: “Verbal description of a concept, permitting its differentiation from other concepts within a system of concepts.”

– International Standard ISO 1087, Terminology – Vocabulary, 1990

• The Semantic Web is about formalizing your definitions

“the Semantic Web, as envisioned by Tim Berners-Lee and many others since, is a logical extension of the current Web that enables explicit [machine-processable] representations of term meanings [concepts]”

– Frankel, David; Hayes, Pat; Kendall, Elisa; McGuinness, Deborah: MDA

Journal July 2004


Formality Spectrum: formal

SAPterm WordNet

"An ontology is an explicit and

formal specification of a shared

conceptualization"

Ontology, e.g, OWL ontology

Informal Formal

Every tomato is red.

for all x ( tomato (x) implies red (x) )


Concept, Object, Designation (term), and Definition

Definition

Designations (terms)

Object

Handy (DE)

cellular phone, cell phone (US) (two variants)

mobile (UK)

A one-piece, hand-

held phone that

includes battery power

and may be used

without any peripheral

power or antenna.

(Nokia)

Concept

term is verbal designation


More on the meaning triangle

morning star

evening star

An example from Gottlob Frege (1848-1925):

different termsdifferent concepts and definitionssame object, the planet Venus


Which terms are of interest?

Common words/terms

Specialist terms

Shared terms

skin

scalpel

doctor

dermatologist

blade

curettage


• “Structured set of concepts established according to the relations between them…”

– International Standard ISO 1087, Terminology – Vocabulary

• Some types of relations:

• Hierarchic

• Generic (subclass, a bird is an animal)

• Partitive (part-whole, a tire is part of a car)

System of Concepts

Note: Superordinate and subordinate can mean any kind of hierarchic relation


Dictionary entry versus term entry

cardinal, the noun, has one entry in the

American Heritage® dictionary with

five senses:

1. a Roman Catholic high-church

official,

2. a color,

3. a bird,

4. a cloak

5. a type of number.


Question 1.2

How would you represent the information in this dictionary entry using concept diagrams?

cardinal, the noun, has one entry in the American Heritage® dictionary with five senses: 1. a Roman Catholic high-church official, 2. a color, 3. a bird, 4. a cloak 5. a type of number.

Choose one answer:

2. As five concepts differentiated by context

3. As five concepts differentiated by subject field

4. As one concept


Answer 1.2

The correct answer is two.

cardinal, the noun, has one entry in the American Heritage® dictionary with five senses: 1. a Roman Catholic high-church official, 2. a color, 3. a bird, 4. a cloak 5. a type of number.

CardinalLanguage: ENCountry: US

((catholic catholic

churchchurch))


((colorscolors))


((textilestextiles))


((mathematicsmathematics))


((ornithologyornithology))

FIVE HOMONYMS


Definitions are historical statements

• heat is “a form of ENERGY, viz. the kinetic and potential energy of the invisible molecules of bodies” OED 2nd edition

• heat is “an elastic material fluid of extreme subtlety attracted and absorbed by all bodies” (OED, same entry as previous definition)

heat heat?


Definition is Social

• Social aspects

– language community

– research

– brain storming

– review

– consensus

Find and use the standardized terminology as decided by experts in the subject field

Discuss in your product development and information development teams how to:

• Find the standards and authorities

• Build up team libraries (textbooks, glossaries, journals, articles …)

• Distribute lists of useful links

• Meet experts at conferences

– and, perhaps, create standard terminology for the industry based on new concepts and products


Summary: Writing Definitions

• Strategies for writing definitions

– Identify and list distinguishing characteristics,

intension

– Use them to write definition

– Use system of concepts

– Genus (super-class) and difference

• Things to keep in mind

– Social awareness

– Purpose and audience

– Choice of terms

– Include illustrations of use

– Include example data for data element definitions


Graphic representation of necessity and sufficiency

super-class subclass equivalent


Possible relationships between two classes

super-class subclass equivalent

overlapping disjoint complement


Ontologies

• Ontologies are about vocabularies and their meanings, with explicit, expressive, and well-defined semantics—possibly machine-interpretable.

• By machine-interpretable we mean that the semantics of the model is semantically interpretable by the machine; in other words, the computer and its software can interpret the semantics of the model directly—without direct human involvement.

• The standard definition for ontologies is “A formal, explicit specification of a shared conceptionalization”.


Ontologies

� According to T. Berners-Lee, J. Hendler, and O. Lassila, an ontology is a taxonomy combined with inference rules.

� Roughly speaking, an ontology is, for a domain, a set of classes and their relationships.

� An ontology is represented in a knowledge representation language (such as a Semantic Web language like RDF/S, DAML+OIL, OWL, or in an ontology language that predates the Semantic Web, such as Ontolingua/KIF/Common Logic, OKBC, CycL, or Prolog).

� Ontologies provide a basis for semantic interoperability.


OntologiesOntologies

A complete ontology includes the same kinds of concepts:

Classes (general things) in the many domains of interest

Instances (particular things)

The relationships among those things

The properties (and property values) of those things

The functions of and processes involving those things

Constraints on and rules involving those things


Ontologies

What does an ontology look like?Class Writer extends Person

Name: String

Nacionality: Country

Birthdate: Date

Deathdate: Date

Movement: LiteraryMovement

Works: Book (multiplicity n)

Class Book extends Work

Title: String

Author: Writer

Class LiteraryMovement

Name: String

Writers: Writer (multiplicity n)Surrealism

Nadja

André Breton


Logic and proofs

• Logic is the discipline that studies the

principles of reasoning

• Formal languages for expressing knowledge

• Well-understood formal semantics

– Declarative knowledge: we describe what

holds without caring about how it can be

deduced

• Automated reasoners can deduce (infer)

conclusions from the given knowledge


An inference example

Forall x (Person(x) => Mortal(x)

So if Person(Socrates) (Socrates is a person),

therefore, Mortal (Socrates) (unfortunately, Socrates is a mortal).

This inference is correct because Forall x (Person(x) => Mortal(x) is a First-Order Logic expression, and because FOL has a formal semantics and syntaxis.

Logical languages �� Inferences can be proof

Logic and proofs

• F12: SEMANTICS and ONTOLOGIES...© 2005-2006 The ATHENA Consortium. 1 • F12: SEMANTICS and...

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