Semantic Web JOSH FLECK What is Semantic Web

Semantic Web JOSH FLECK

What is Semantic Web? �Movement led by W 3 C 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 resource �Used as an identifier so that interactions can take 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. w 3. 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 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 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: sub. Class. Of: 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 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/Faceted. Search? 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

Rel. Finder �http: //www. visualdataweb. org/relfinder. p hp

Conclusion �Web of Data �Stores 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/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/Semantic. Web. Action. pdf � Mirhaji, P. (2007, March). Semantic Web Use Cases and Case Studies. Retrieved March 25, 2012, from W 3 C: www. w 3. org/2001/sw/sweo/public/Use. Cases/Uni. Texas � 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 W 3 C: www. w 3. org/TR/rdf-schema/#ch_properties � Semantic Web. (n. d. ). Retrieved March 25, 2012, from W 3 C: http: //www. w 3. 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 W 3 C: http: //www. w 3. 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 w 3 schools. com: www. w 3 schools. com/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 W 3 C: http: //www. w 3. org/2001/sw/sweo/public/Use. Cases/NRK/