Introduction to the Semantic Web

Lalana Kagal

6.898: Transparency and Accountability Architectures


World Wide Web

What is the Web?

  • Information represented in natural language
  • Documents contain graphics, multimedia, layouts
  • Suitable for humans

Properties of the Web

  • Is a web of documents connected by anchors
  • URIs are used for documents and anchors
  • Standards include HTTP, xHTML, SVG, DOM, XSLT...
Web of interconnected documents

Semantic Web

What is the Semantic Web

  • Web resources include meta data in a machine understandable format such as XML
  • Helps in better searching, making inferences, etc.
  • Extends existing web and does not replace it

Properties of the Semantic Web

  • Is a web of data
  • URIs are used for documents, concepts, properties that connect concepts
  • Standards include RDF, OWL, SPARQL, RIF...
Web of concepts, their properties,
	   and relationships

Uniform Resource Identifiers (URIs)

  • On the Web
    • A URI identifies a document
    • HTTP allows a client to get a representation of the document
  • On the Semantic Web
    • A URI identifies any thing: Instead of using the word "colour" the concept <> is used
    • Concepts such as car, parking garage, university
    • Properties of these concepts such as color, number of spaces, location of the university

more circles and arrows diagram

The element of the Semantic Web

A database's row, column and cell are subject,
					 property and value.

Relational database

arrow tail, body and head are l are subject,
					 property and value.



Representing RDF

Modeling RDF

Similar to Object Oriented Programming

	 public class Course {
     public Person instructor;
     public string location;
	 public Person student;
	 // constructor
	 public Course(Person i, string l) {
	   instructor = i;
	   location = l;
	 public void AddStudent(Person s) {

	 public List GetStudents() {

Modeling RDF data

In RDF you can use rdf and rdfs namespaces to define concepts and their properties

   @prefix rdf: <> .  
   @prefix rdfs: <> .

	 Course rdf:type rdfs:Class.
	 instructor rdf:type rdf:Property.
	 instructor rdfs:domain Course.
	 instructor rdfs:range Person.
	 student rdf:type rdf:Property.
	 student rdfs:domain Course.
	 student rdfs:range Person.	   
	 location rdf:type rdf:Property.
	 location rdfs:domain Course.

Representing RDF

More shortcuts, rdf:type = a, property-values of same concept can be separated by ';'

	  6.898 a Course;
	     instructor <>;
 	     instructor <>;
	     student <>;
	     location <>.

Friend Of A Friend (FOAF)

Reading/Browsing RDF data


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