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JOSH FLECK
Semantic Web
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 Berners-Lee, 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 resourceUsed as an identifier so that interactions can
take placeCan be classified as a locator (URL), name
(URN), or bothName provides a resource’s identity and
locator provides an addressURN 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 RDFTwo 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 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-typesrdf:XMLLiteral: The class of XML literal valuesrdf:Property: The class of RDF Properties
Core Components of RDFS Properties
rdfs:range: Used to declare the class or data-type of the 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 vocabulariesDefines the terms, data, and relationships of
dataMost common standard is Web Ontology
Language (OWL)
Components of Ontology
Individuals: instances or objects (the basic or "ground 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 FalseDESCRIBE 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 meaningGathers information from different sourcesRather than just having the details together
on the screen, they will have a relationship in the code
Challenges
VastnessVaguenessUncertaintyInconsistencyDeceit
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
CensorshipDoubling output formats
Examples of Semantic Web
DBpediaFOAFDigital music archivesSAPPHIRERelfinder
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.php
Conclusion
Web of DataStores meaning
Questions?
References
Christian Bizer, T. H.-L. (2009). Linked Data - The Story So Far. Retrieved March 25, 2012, from Tom Heath: http://tomheath.com/papers/bizer-heath-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 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-sparql-query/
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/