Semantic Web
for the
Working Ontologist
Dean Allemang
Jim Hendler
SNU IDB laboratory
Working Ontology Contents
■
Chapter 1
What is the Semantic Web?
■
Chapter 2
Semantic Modeling
■
Chapter 3
RDF-The Basis of the semantic Web
■
Chapter 4
Semantic Web Application Architecture
■
Chapter 5
RDF and Inferencing
■
Chapter 6
RDF Schema
■
Chapter 7
RDFS-Plus
■
Chapter 8
Using RDFS-Plus in the Wild
■
Chapter 9
Basic OWL
■
Chapter 10 Counting and Sets in OWL
■
Chapter 11 Using OWL in the Wild
■
Chapter 12 Good and Bad Modeling Practices
■
Chapter 13 OWL Levels and Logic
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Chapter 2 Semantic Modeling
■
1. Modeling for Human Communication
■
2. Explanation and Prediction
■
3 Mediating Variability
■

3.1. Variation and Classes

3.2. Variation and Layers
4. Expressivity in Modeling
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Introduction
■
■
The Semantic Web

Uses AAA Slogan, open world assumption, nonunique naming for Network
Effect

These ideas are good for Information gathering and sharing

But they make confusion, disagreement, and conflict
Web infrastructure have to solve these problem for information sharing,
cooperation and collaboration

The answer is Modeling!
Semantic Web
Modeling
Semantic Web
Confusion
Information sharing
Disagreement
Cooperation
Conflict
Collaboration
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Introduction: Modeling
■
Modeling is the process of organizing information for community use
■
Modeling supports this in three ways
■
1) Framework for human communication (→Section 1)

■
2) Explain and make predictions (→ Section 2)

■
It allows people to collaborate on their understanding
It helps individuals make their own judgments
3) Structure for managing varying viewpoints (→ Section 3)

It is essential to fostering understanding in a web environment
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Dean Allemang, Jim Hendler
1. Modeling for Human Communication
3 Functions of Modeling
1) Framework for human communication
It allows people to collaborate on their understanding
2) Explain and make predictions
It helps individuals make their own judgments
3) Structure for managing varying viewpoints
It is essential to fostering understanding in a web environment
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Dean Allemang, Jim Hendler
1. Modeling for Human Communication
■
Human Communication is a goal for Modeling

It is the fundamental requirement for building a Semantic Web

It allows people to contribute to a growing body of knowledge and then draw
from it
Human Communication
Semantic Web
Model
draw from it
contribute knowledge
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1. Modeling for Human Communication
■
■
Formality of Modeling

There are 2 types of Model for Human Communication

Formal Model, Informal Model
example
Formal Model
Informal Model
National law
private agreements
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1. Modeling for Human Communication
■
Informal Models

Community tagging: a more collaborative style of document modeling
Community tagging style
Informal Model
It provides an informal organization to a
large body of heterogeneous information
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1. Modeling for Human Communication
■
Heavily layered Models

Informal model have the risk that its meaning will not be clear, so further
modeling must be done to clarify that

Further models are required to provide common context to explicate the
shared meaning
Informal
Model
Because of the inherent
ambiguity of natural language
Semantic Web for the Working Ontologist
Informal
Model
Need next layer of
commentary
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Heavily
Layered
Models
Repeat until it clarifies the
meaning
Dean Allemang, Jim Hendler
2. Explanation and Prediction
3 Functions of Modeling
1) Framework for human communication
It allows people to collaborate on their understanding
2) Explain and make predictions
It helps individuals make their own judgments
3) Structure for managing varying viewpoints
It is essential to fostering understanding in a web environment
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Dean Allemang, Jim Hendler
2. Explanation and Prediction
■
Models are used to organize human thought in the form of explanations
■
Explanation
■

Explanation makes it easier to reuse a model in whole or in part

Explanation relates a phenomenon to “first principles”
Formalism

Objective form, and the rules that govern how it works

Formal modes are the bread and butter of mathematical modeling
Formal Model
Explanation
Mathematical modeling
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2. Explanation and Prediction
■
Prediction

Formalisms can also be used for predictions

Given a description of a situation in some formalism, the same rules that
govern transformations in proofs can be used to make predictions
Formal Modeling
Prediction
1+2=3
1+1+1=3
Formal Modeling
1+1=2
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2. Explanation and Prediction
■
Therefore, Formal modeling has vary different social dynamic than informal
modeling

Because there is an objective reference to the model(the formalism)

There is no need for the layers of interpretation
Informal Model
vs
Formal Model
Formal Model
Informal
Model
Heavily
Layered
Models
Need layers of interpretation
to avoid ambiguity
Semantic Web for the Working Ontologist
Need to follow formalism
for explanation and prediction
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Dean Allemang, Jim Hendler
3. Mediating Variability
3 Functions of Modeling
1) Framework for human communication
It allows people to collaborate on their understanding
2) Explain and make predictions
It helps individuals make their own judgments
3) Structure for managing varying viewpoints
It is essential to fostering understanding in a web environment
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Dean Allemang, Jim Hendler
3. Mediating Variability
■
Variability

The dynamics of the network effect require the ability to represent a variety of
opinions

A good model organizes those opinions so that the things that are common
can be represented together, while the things that are distinct can be
represented as well
IAU
website
astrologers
website
8 planets
8 planets
Semantic Web for the Working Ontologist
9 planets
9 planets
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Dean Allemang, Jim Hendler
3. Mediating Variability
■
Ways to accommodate these different view points
■
1) Control the Web so that only that position is supported

Where a small group or even a single person acts as the db admin

Not appropriate for the Web because it does not allow for the AAA slogan
website
admin
IAU
astrologer
s
website
8 planets
9 planets
9 planets
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8 planets
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Dean Allemang, Jim Hendler
3. Mediating Variability
■
2) Allow each one to be represented separately, with no reference to one
another at all

Basis of an informal approach, and it indeed describes the state of the
document web as it is today

It would be the responsibility of the information consumer to understand

Model must allow for each of these differing viewpoints to be expressed
website
8 planets
website
IAU
9 planets
8 planets
astrologers
9 planets
Semantic Web for the Working Ontologist
consumers
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Dean Allemang, Jim Hendler
3.1. Variation and Classes
■
The Semantic Web standards also use this idea of class hierarchy for
representing commonality and variability (OOP)

Organizing commonality and variability in components

But, Unlike OOP, Semantic Web isn’t focused on s/w representation
▶

Classes are not defined in terms of behaviors of functions
But the notion of classes and subclasses remains, and it plays much the
same role
High-level classes
Represent commonality among
a large variety of entities
lower-level classes
Represent commonality among
a small, specific set of things
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3.1. Variation and Classes: Examples
■
Solar System Body
SSB
IAU
■
■
IAU:Planet
The 2006 IAU definition of planet

1. It is in orbit around the sun

2. It has sufficient mass to be nearly round

3. It has cleared the neighborhood around its orbit
By IAU definition,

Planet: satisfies conditions 1 + 2 + 3

Pluto(dwarf planet) : satisfies conditions 1 + 2 (not 3!)

SSSB(small solar system body): satisfies condition 1
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3.1. Variation and Classes: Examples
■

■
astro:Planet
Twentieth-century astronomy
Not quite as organized as IAU definition
Astrology

astrologers
horo:Planet
Not quite as organized as IAU definition
SSB
astro:Planet
Semantic Web for the Working Ontologist
horo:Planet
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IAU:Planet
Dean Allemang, Jim Hendler
3.1. Variation and Classes: Examples
■
We can go further in this modeling when we observe that there are only eight
IAU:Planets, and each one is also a horo:Planet and an astro:Planet
■
Thus, we can say that IAU:Planet is a subclass of both horo:Planet and
astro:Planet
SSB
horo:Planet
astro:Planet
IAU:Planet
■
In this way, we can model the commonality among entities (at the high level)
while respecting their variation (at a low level)
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Dean Allemang, Jim Hendler
3.2. Variation and Layers
■
If we can’t structure the entities they are describing into a class model?
■
The Semantic Web provides an elegant solution to this problem

The basic idea is that any model can be built up from contributions from
multiple sources

The entire model is the combination of all the layers
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Dean Allemang, Jim Hendler
3.2. Variation and Layers: Examples
Information about Pluto of astrologers
Information about Pluto of astronomers
Rebirth
Methane
signifies
madeOf
Pluto
Pluto
signifies
Regeneration
Semantic Web for the Working Ontologist
madeOf
prefSymbol
prefSymbol
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Nitrogen
Dean Allemang, Jim Hendler
3.2. Variation and Layers: Examples
■
The simplest way is to simply merge the two models into a single one that
includes all the information from each model
prefSymbol
Methane
Rebirth
signifies
madeOf
Pluto
madeOf
signifies
Nitrogen
Regeneration
prefSymbol
■
But merging models has a draw back: machine can’t figure out inconsistency
between “ prefSymbol” and “ prefSymbol”

This is the reason why we need to publish models on the Semantic Web
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4. Expressivity in Modeling
■
Trade-off when we model

People Need different tool: This difference is one of Level of expressivity
least expressive
H2O
most expressive
H
O
H
Simple, but widely used
1. Two (H), One (O)
More expressive, but more complex
1. Two (H), One (O)
1. Two (H), One (O)
2. It can break into (H), (OH)
But not (HH)
2. It can break into (H), (OH)
But not (HH)
3. Shows chemical&physical structure
■
More expressive model is not superior one

Different expressive model are just used for different purposes
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4. Expressivity in Modeling
■
The Semantic Web

providing a number of modeling languages that differ in their level of
expressivity
least expressive
RDF
Semantic Web for the Working Ontologist
most expressive
RDFS
RDF-PLUS
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OWL
Dean Allemang, Jim Hendler
4. Expressivity in Modeling
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RDF(Resource Description Framework) ch3, ch4, ch5

The basic framework

providing a mechanism for

■
▶
Allowing anyone to make a basic statement about anything
▶
Layering these statements into a single model
Having been a recommendation from the W3C since 2003
RDFS(RDF Schema Language) ch6


A language with the expressivity
▶
to describe the basic notions of commonality and variability
▶
Familiar form object languages and other class systems-namely classes,
subclasses, and properties
RDFS has been a W3C recommendation since 2003
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4. Expressivity in Modeling
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■
RDF-PLUS ch7, ch8

A subset of OWL

More expressive than RDFS

Without the complexity of OWL
OWL(Web Ontology Language) ch9, ch10, ch11, ch12, ch13

Brings the expressivity of logic to the Semantic Web

To allow modelers to express detailed constraints between classes, entities,
and properties

Being adopted as a recommendation by the W3C in 2003
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