Transcript Some Thoughts to Consider 1

Some Thoughts to Consider 6
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What is the difference between Artificial
Intelligence and Computer Science?
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What is the difference between Artificial
Intelligence and Software Engineering?
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What is the difference between Artificial
Intelligence and Object Technology?
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Why would some people call the ‘Semantic
Web’ the ‘Pedantic Web’?
Heuristic - An Important Concept
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The word ‘heuristic is derived from a Greek
word meaning ‘to find’ or ‘to discover’.
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Some people use heuristic as the opposite of
algorithmic. Newell and Simon: “A process
that may solve a given problem, but offers no
guarantees of doing so, is called a heuristic for
that problem.”
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Some people view heuristics as ‘rules of
thumb’ that domain experts use to generate
good solutions without exhaustive search. This
view paved the way for rule-based expert
systems.
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Some generalize heuristic to mean ‘knowledge
about a problem solution’.
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Currently, according to Russell and Norvig,
heuristic is most often used as an adjective,
referring to any technique that improves the
average-case performance on a problemsolving task, but does not necessarily improve
the worst-case performance.
Main Points of Chapter 8
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Knowledge representation languages should be declarative,
compositional, expressive, context-independent, and
unambiguous.
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Logics differ in their ontological commitments and
epistemological commitments. While propositional logic commits
only to the existence of facts, first-order logic commits to the
existence of objects and relations and thereby gains expressive
power.
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A possible world, or model, for first-order logic is defined by a
set of objects, the relations among them, and the functions that
can be applied to them.
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Constant symbols name objects, predicate symbols name
relations, and function symbols name functions. An
interpretation specifies a mapping from symbols to the model.
Complex terms apply function symbols to terms to name an
object. Given an interpretation and a model, the truth of a
sentence is determined.
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An atomic sentence consists of a predicate applied to one or
more terms; it is true just when the relation named by the
predicate holds between the objects named by the terms.
Complex sentences use connectives just like propositional logic,
and quantified sentences allow the expression of general rules.
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Developing a knowledge base in first-order logic requires a careful
process of analyzing the domain, choosing a vocabulary, and
encoding the axioms required to support the desired inferences.
GTTTOT in First-Order Logic
case(8, 8, downtown, good).
distance(D)
time(T)
location(L)
weather(W)
:- case(D, _, _, _).
:- case(_, T, _, _).
:- case(_, _, L, _).
:- case(_, _, _, W).
means(X) :- distance(D), D > 5, X = drive.
means(X) :- distance(D), D > 1, time(T), T < 15, X = drive.
means(X) :- distance(D), D > 1, time(T), T > 15, X = walk.
action(X) :- means(drive), location(downtown),
X = takecab.
action(X) :- means(drive), not location(downtown), X = drivecar.
action(X) :- means(walk), weather(good),
X = walk.
action(X) :- means(walk), weather(bad),
X = walkwithcoat.
The Semantic Web
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Tim Berners-Lee’s original vision of the Web
was more than the information space that we
see today.
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In his own words:
“The Web was designed as an information
space, with the goal that it should be useful not
only for human-human communication, but also
that machines would be able to participate and
help. One of the major obstacles to this has
been the fact that most information on the Web
is designed for human consumption, and even
if it was derived from a database with well
defined meanings (in at least some terms) for
its columns, that the structure of the data is not
evident to a robot browsing the web. Leaving
aside the artificial intelligence problem of
training machines to behave like people, the
Semantic Web approach instead develops
languages for expressing information in a
machine processable form.”
Semantic Web Resources
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What is a ‘Semantic Web’?
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W3C Characterization of Semantic Web
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Presentation by Tim Berners-Lee
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Scientific American Article
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Semantic Web: Info, Tools, Techniques
OIL & OWL
Semantic Web Ontology Languages
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OIL - Ontology Inference Layer.
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OWL - Web Ontology Language.
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The 3 roots of OIL & OWL:
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Web languages (XML, RDF)
Frame based systems
Description logics
OIL & OWL Resources:
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OIL Home Page
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OIL: An Ontology Infrastructure for the
Semantic Web
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OWL: The Web Ontology Language
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W3C Web Ontology Language Guide
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Introduction to OWL 1
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Introduction to OWL 2