Information Retrieval
Summary 26-11-03
Introduction
The class started with an explanation of the Scientific American Article about the
semantic web. It’s an overview of the bigger picture of the semantic web. What is the
difference between the semantic web and the WWW? What is the main purpose of the
semantic web? And.. how is it constructed?
The class was focused on finding answers to these questions.
An important issue to consider is that the theory of the semantic web is based on a
concept of ‘ontology’. The term ontology1 “is a specification of a conceptualization. That
is, an ontology is a description (like a formal specification of a program) of the concepts
and relationships.”
Ontologies can exist without the semantic web, the semantic web however cannot exist
without ontologies.
Main Purpose?
The real power of the Semantic Web will be realized when people create many
programs that collect Web content from diverse sources, process the information and
exchange the results with other programs. The effectiveness of such software agents will
increase exponentially as more machine-readable Web content and automated services
(including other agents) become available.
1
http://www-ksl.stanford.edu/kst/what-is-an-ontology.html
Semantic Web:
Definition: "The Semantic Web is an extension of the current web in which
information is given well-defined meaning, better enabling computers and people
to work in cooperation." 2
Advantage: The advantage of the semantic web over the www is, that it is a
problem of the www that it is difficult to use the data on the www in the ways that
one wants, while in the semantic web it is easier to access certain data one
seeks.
Semantic Web vs. WWW: The advantage of the semantic web over the www is,
that it is a problem of the www that it is difficult to use the data on the www in the
ways that one wants, while in the semantic web it is easier to access certain data
one seeks. The Semantic Web is dissimilar in many ways from the World Wide
Web, including that you can't just point people to a Web site for them to realise
how it's working, and what it is. However, there have been a number of small
scale Semantic Web applications
The Big Picture
2
Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001
Components of the big Picture3:
Agent: A semantic web agent has no artificial intelligence but is a calculating software
program, the semantics are encoded into the web pages using software for writing
semantic webpages and data.
Ontologies: An ontology is the "explicit specification of a conceptualization", which
provides all the required terminology, and a basis for a community of interest for
information exchange.
Web page annotation tool: The ontology defines the terms that are possible to use for
annotation information in webpages, using the DAML language. The proposed OnToAgents Webpage Annotation Tool has means to browse the ontology and to select
appropriate terms of the ontology map to mark-up sections of a webpage. The webpage
annotation process creates a set of annotated webpages.
End user: information-seeking users can give specific retrieval tasks to an OnTo-Agent,
or they can query a Community Web Portal for immediate access to the information.
The Agent itself needs several sub-components, specifically the OnTo-Agents Inference
System for the evaluation of rules and queries and general inferences, the OnTo-Agents
Ontology Articulation Toolkit for mediation among information obtained from different
ontologies. The data in from the annotations can be used to construct additional
websites: a Community Web Portal, that presents a community of interest to the outside
word in a concise manner.
Languages for the Semantic Web:
computer languages for the semantic web:
DAML-OIL
SHOE
XML = eXtensible Markup Language
RDF = Resource Description Framework
OIL = Ontology Interchange Language
DAML4
The DAML language is being developed as an extension to XML and the Resource
Description Framework (RDF). The latest release of the language (DAML+OIL) provides
a rich set of constructs with which to create ontologies and to markup information so that
it is machine readable and understandable.
3
4
http://www-db.stanford.edu/OntoAgents/
http://www.daml.org/about.html
Papers
1. T. Berners-Lee et al. (2001). The semantic web The Scientific American
http://www.sciam.com/article.cfm?articleID=00048144-10D2-1C7084A9809EC588EF21
Links
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The semantic web community portal . http://www.semanticweb.org/
W3C Semantic Web Activity . http://www.w3.org/2001/sw/
The semantic web: an introduction. http://infomesh.net/2001/swintro/
Creation of the semantic web: semantic markup .
http://www.cs.umd.edu/users/hendler/sciam/walkthru.html