Transcript Semantic Web

Semantic Web
JOSH FLECK
What is Semantic Web?
 Movement led by W3C that promotes common
formats for data on the web
 Describes things in a way that computer applications
can understand it
 Describes the relationship between things and
properties of things
 Tries to organize and structure the current Web’s
documents into a logical group or web of data
What is Semantic Web?
 "If HTML and the Web made all the online
documents look like one huge book, RDF, schema,
and inference languages will make all the data in the
world look like one huge database“ - Tim BernersLee, Weaving the Web, 1999
 Uses Linked Data
Semantic Web Stack
Linked Data
 Uses the Web to create links between data from
different sources
 Refers to data published on the Web in way that is
machine-readable, its meaning is explicitly defined,
it is linked to other external data sets, and it can be
linked to from external data sets
 Allows applications to grab large amounts of related
data
 Is created by using URIs and RDF
Uniform Resource Identifier (URI)
 String of characters that represents a resource
 Used as an identifier so that interactions can take
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place
Can be classified as a locator (URL), name (URN), or
both
Name provides a resource’s identity and locator
provides an address
URN example: “XMLSchema”
URL example:
http://www.w3.org/2001/XMLSchema
Resource Definition Framework (RDF)
 Standard built on top of XML to describe
information about resources on the Web
 Intended for representing metadata about Web
resources ex: title, author, data of a Web page
 Intended to be used by applications rather than
being seen by users
 Puts information of a resource into triple expressions
Triple Expressions
Extensible Markup Language (XML)
 Used to encode the RDF
 Two types of XML nodes in a RDF/XML document
 Resource Nodes
 Property Nodes
RDF Schema (RDFS)
 Set of classes with certain properties using RDF
 Provides basic elements for the description of
ontologies, used to structure RDF resources
 These resources can be saved in a triple to reach
them with the query language SPARQL
Core Components of RDFS Classes
 rdfs:Resource: All things described by RDF are called
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resources, and are instances of the class
rdfs:Resource
rdfs:Class: This is class of resources that are RDF
classes
rdfs:Literal: The class of literal values such as strings
and integers
rdfs:Datatype: The class of data-types
rdf:XMLLiteral: The class of XML literal values
rdf:Property: The class of RDF Properties
Core Components of RDFS Properties
 rdfs:range: Used to declare the class or data-type of the
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object in a triple
rdfs:domain: Used to declare the class of the subject in a
triple
rdfs:type: Used to state that a resource is an instance of a
class
rdfs:subClassOf: Used to state that all resources related
by one property are also related by another
rdfs:label: Used to provide a human-readable version of
a resource’s name
rdfs:comment: Used to provide a human-readable
description of a resource
Ontology
 Also known as RDF vocabularies
 Defines the terms, data, and relationships of data
 Most common standard is Web Ontology Language
(OWL)
Components of Ontology
 Individuals: instances or objects (the basic or "ground
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level" objects)
Classes: sets, collections, concepts, classes in
programming, types of objects, or kinds of things
Attributes: aspects, properties, features, characteristics,
or parameters that objects (and classes) can have
Relations: ways in which classes and individuals can be
related to one another
Function terms: complex structures formed from certain
relations that can be used in place of an individual term
in a statement
Components of Ontology
 Restrictions: formally stated descriptions of what
must be true in order for some assertion to be
accepted as input
 Rules: statements in the form of an if-then
(antecedent-consequent) sentence that describe the
logical inferences that can be drawn from an
assertion in a particular form
Components of Ontology
 Axioms: assertions (including rules) in a logical form
that together comprise the overall theory that the
ontology describes in its domain of application
 Events: the changing of attributes or relations
SPARQL
 Able to retrieve and manipulate data stored in RDF
 Allows for a query to consist of triple patterns,
conjunctions, disjunctions, and optional patterns
 Implementations for multiple programming
languages exist
SPARQL Queries
 SELECT Query: results are returned in a table format
 CONSTRUCT Query: results are returned in RDF
form
 ASK Query: results are either True or False
 DESCRIBE Query: returns a RDF graph containing
RDF data about resources
SPARQL
Rule Interchange Format
 Originally envisioned as a rules layer for the
semantic web
 Instead, it recognizes that there are many rule
languages and what is needed to exchange rules
between them
Future of the Web
 Gives information on the Web meaning
 Gathers information from different sources
 Rather than just having the details together on the
screen, they will have a relationship in the code
Challenges
 Vastness
 Vagueness
 Uncertainty
 Inconsistency
 Deceit
Disadvantages of Semantic Web
 The Web currently uses HTML while Semantic Web
uses RDF
 Semantic web is mostly unknown and there are few
people that know how to write a web page in RDF
 Censorship
 Doubling output formats
Examples of Semantic Web
 DBpedia
 FOAF
 Digital music archives
 SAPPHIRE
 Relfinder
DBpedia
 Allows users to find answers to questions that are
spread across many different Wikipedia pages
 http://wiki.dbpedia.org/FacetedSearch?v=pjv
Friend of a Friend (FOAF)
 Uses RDF to describe the relationships people have
to other people and things around them
 Lets intelligent agents make sense of the thousand of
connections people have with each other, their jobs,
and items important to their lives
 Example of how Semantic Web attempts to make use
of the relationships in a social context
Digital Music Archive
 Digitize the huge music material at the Norwegian
National Broadcaster (NRK)
 Use the repository asset in new productions, with
better search and access
 Semantic Web is used to manage the huge amount
of metadata, and provide easy and quick access to
the asset
SAPPHIRE
 An integrated biosurveillance system; integrates data
from multiple sources
 Data can be viewed from many different perspectives
(disease surveillance, environmental protection,
biosecurity and bioterrorism, veterinary surveillance,
etc.)
 SAPPHIRE receives reports every 10 minutes on
emergency room cases, patients’ symptoms, health
records, and clinicians’ notes from other hospitals in
the area
RelFinder
 http://www.visualdataweb.org/relfinder/relfinder.p
hp
Conclusion
 Web of Data
 Stores meaning
Questions?
References
 Christian Bizer, T. H.-L. (2009). Linked Data - The Story So Far. Retrieved
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March 25, 2012, from Tom Heath: http://tomheath.com/papers/bizerheath-berners-lee-ijswis-linked-data.pdf
Lee Feigenbaum, I. H. (2009, January 19). The Semantic Web in Action.
Retrieved March 25, 2012, from Scientific American:
http://people.cs.kuleuven.be/~danny.deschreye/SemanticWebAction.pdf
Mirhaji, P. (2007, March). Semantic Web Use Cases and Case Studies.
Retrieved March 25, 2012, from W3C:
www.w3.org/2001/sw/sweo/public/UseCases/UniTexas
Ontology (information science) - Wikipedia, the free encyclopedia. (n.d.).
Retrieved April 15, 2012, from Wikipedia, the free encyclopedia:
en.wikipedia.org/wiki/Ontology_(information_science)
RDF Schema. (n.d.). Retrieved April 15, 2012, from W3C:
www.w3.org/TR/rdf-schema/#ch_properties
Semantic Web. (n.d.). Retrieved March 25, 2012, from W3C:
http://www.w3.org/standards/semanticweb/
References
 Semantic Web - Wikipedia, the free encyclopedia. (2012). Retrieved
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March 2012, 8, from Wikipedia, the free encyclopedia:
http://en.wikipedia.org/wiki/Semantic_Web
SPARQL Query Language for RDF. (2008, January 15). Retrieved
March 25, 2012, from W3C: http://www.w3.org/TR/rdf-sparqlquery/
Tauberer, J. (2008, January). What is RDF and what is it good for?
Retrieved March 25, 2012, from Resource Description Framework:
http://www.rdfabout.com/intro/
The Semantic Web. (n.d.). Retrieved March 25, 2012, from
w3schools.com: www.w3schools.com/web/web_semantic.asp
Tønnesen, D. R. (2007, September). Case Study: A Digital Music
Archive (DMA) for the Norwegian National Broadcaster (NRK)
using Semantic Web techniques. Retrieved March 25, 2012, from
W3C: http://www.w3.org/2001/sw/sweo/public/UseCases/NRK/