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/