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The Semantic Web

Class 16 

PDF Handout: class16_the_semantic_web.pdf



The Quest for Information

The early Web gave us directories and search engines in order to find information. Web developers can code in meta data is assist in finding information. Social searches may aid in our ability to find what we are looking for.

No doubt, you have tried to find some specific piece of information, only to be frustrated with thousands of links to click on, which, in the end, did not produce the desired result.

The Semantic Web was an idea put forth by Tim Berners-Lee many years ago which would solve this problem by developing a Web where data can be integrated and shared.


The Semantic Web

The word semantic stands for the “meaning of”. The semantic of something is the meaning of something. The Semantic Web will provide the tools which will enable us to describe things in a way that computers can understand. It will do this by generating “metadata” – machine readable data that describes other data. The goal of the Semantic Web is to integrate “data” from diverse sources into meaningful “information” so that automated processing becomes possible.



Intro the the Semantic Web - 6 min

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photo of Time Berners-Lee"The Semantic Web looks at integrating data across the Web. The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people. For the Web to scale, tomorrow's programs must be able to share and process data even when these programs have been designed totally independently. The Semantic Web is a vision: the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications."

Read full article at http://www.scientificamerican.com/article.cfm?id=the-semantic-web


Tim Berners Lee on the Semantic Web - 8:30 min 

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Human vs Computer Intelligence

Typical Web pages use text, images and page layout to present information in a way that we can understand. Computers are used to create, search and display information on the Web, but the computers themselves really can't make sense of all this information. They can't read, see relationships or make decisions like we can.


Where the Semantic Web Comes In

The Semantic Web proposes to enable computers to be more able to understand meaning. Most of the content on the Web is designed for humans to read. It is not very easy for computer programs to interpret that information meaningfully. HTML does not tell us anything about the subject and nature of the content. The goal of the Semantic Web is to come up with some standards to express better the meaning of information so that computers can understand it and use it effectively. Some people refer to the Semantic Web as Web 3.0.


Logo of the W3C and Semantic Web

The Semantic Web is really an extension, not a replacement, of the World Wide Web. It provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries.


It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. While some websites are already using Semantic Web concepts, a lot of the necessary tools are still in development.

The real power of the Semantic Web will be realized when people create many programs that collect Web content from diverse sources, process the information and exchange the results with other programs. The effectiveness of such software agents will increase exponentially as more machine-readable Web content and automated services (including other agents) become available


The Semantic Web is about two things:

·         Common formats for integration and combination of data drawn from diverse sources, where on the original Web mainly concentrated on the interchange of documents

·         Language(s) for recording how the data relates to real world objects


Semantic Web Technologies

      1.     XML- Xtensible Markup Language

2.     RDF - Resource Description Framework . 

3.     Ontologies  - collections of information



  RDF is a markup language and a W3C Specification for describing resources on the Web.

Putting information into RDF files makes it possible for computer programs (ie. spiders) to search, discover, find, collect, analyze and process information from the Web. RDF was designed to provide a common way to describe information so it can be read and understood by computer applications. It is not meant to display information.


RDF Schema

Extends the RDF language by the addition of classes and properties for better information descriptions.



The Simple Protocol and RDF Query Language (SPARQL) is a SQL-like language for querying RDF data.


Web Ontology Language -  OWL - http://www.w3.org/TR/owl-features/


The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans.




Working with the XHTML Document

RDFa (or Resource Description Framework - in - attributes) is a set of extensions to XHTML which is now a W3C Recommendation. RDFa uses attributes from XHTML's meta and link elements, and generalizes them so that they are usable on all elements. This allows you to annotate XHTML markup with semantics. A simple mapping is defined so that RDF triples may be extracted.



RDFa Basics - 9:30 min 

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