Introduction To Semantic Web

Princess Nora University Net535

What is the Semantic Web? Background Components of the Semantic Web Why the Semantic Web is needed Uses of the Semantic Web Implementing the Semantic Web Examples Conclusion

Overview

As we know today web is linked many documents made with computer but is intended to humans understanding only !!!

Even though the web documents are made with computers, computers can NOT understand the content of these documents. They can't read, see relationships or make decisions like human can. !!!

Most of the Search Engines are based on keywords which return not accurate and precise results !!!

Web of Today

A framework that: ◦ Adds meaning to data◦ Provides a mechanism for organizing, interpreting,

and making use of that meaning

What is the Semantic Web?

The Semantic Web is "an extended web of machine-readable information and automated services that amplify the Web far beyond current capabilities" (Daconta et al., 2003)

Semantic means the study of the meaning

“The Semantic Web is a major research initiative of the World Wide Web Consortium (W3C) to create a metadata-rich Web of resources that can describe themselves not only by how they should be displayed (HTML) or syntactically (XML), but also by the meaning of the metadata.”

W3C Semantic Web Page An enhancement to the current Web, not a replacement “The Semantic Web is an extension of the current web in

which information is given well-defined meaning, better enabling computers and people to work in cooperation.”

The Semantic Web, Scientific American, May 2001 by Tim Berners-Lee et al

Semantic Web

The term “Semantic Web” refers to W3C’s vision of the Web of linked data. Semantic Web technologies enable people to create data stores on the Web, build vocabularies, and write rules for handling data. Linked data are empowered by technologies such as RDF, SPARQL, OWL, and SKOS.

Semantic Web Cont’d

It is a vision for the future Web (a web of meaning — semantics); originally defined by Tim Berners-Lee (aka father of the Web).

It is not a separate web, but an extension of the current one.

It provides a way for machines to get much better at being able to process and understand the data that they merely display at present.

It is a web on which machine reasoning can become ubiquitous and powerful.

It describes an emerging set of standards, markup languages, and related processing tools.

So Semantic Web

1968 – Internet used as a communications network by DOD

1989 – Tim Berners-Lee (and others) at CERN develop HTML

Early 1990s – Web browsers created to interpret HTML

1996 – XML developed 1990s+ – Tim Berners-Lee & W3C continue

to pursue development the Semantic Web

Background

Example

The agent would do this not by looking at pictures and reading descriptions like a person does, but by searching through

metadata that clearly identify and define what the agent needs to know.

Metadata are simply machine-readable data that describe other data.

In the Semantic Web, metadata are invisible as people read the page, but they're clearly visible to computers.

Metadata can also allow more complex, focused Web searches with more accurate results. To paraphrase Tim Berners-Lee, inventor of the World Wide Web, these tools will let the Web -- currently similar to a giant book become a giant database.

Why Semantic web cont’d .

The current Web remains largely unstructured (e.g., company)

Large amounts of information remain unavailable

Why the Semantic Web is Needed

Wikipedia describes the purpose of the Semantic Web as follows:

Humans are capable of using the Web to carry out tasks such as finding the Arabic word for “cat”, reserving a library book, and searching for a low price on a DVD.

However, a computer cannot accomplish the same tasks without human direction because web pages are designed to be read by people, not machines.

The semantic web is a vision of information that is understandable by computers, so that they can perform more of the tedious work involved in finding, sharing and combining information on the web.

Semantic Web Purpose

Four major components:

1. XML )eXtensible Markup Language)

XML is a markup language likehypertext markup language (HTML), which you're probably somewhat familiar with from surfing the Web. HTML governs the appearance of the information you look at on the Web. XML complements (but does not replace) HTML by adding tags that describe data. These tags are invisible to the people who read the document but visible to computers.

Components of the Semantic Web

2. Resource Description Framework (RDF)

RDF does exactly what its name indicates -- using XML tags, it provides a framework to describeresources. In RDF terms, pretty much everything in the world is a resource. This framework pairs the resource (any noun, like Anakin Skywalker or the "Star Wars" trilogy) with a specific item or location on the Web so the computer knows exactly what the resource is. Clearly identifying resources keeps the computer from doing things like confusing Anakin Skywalker with Sebastian Shaw or Hayden Christiansen, or the original trilogy with the One-Man "Star Wars" Trilogy.

Components of the Semantic Web(cont’d)

3.Ontologies

There are two related tools for helping a computer understand human vocabulary. An ontology is simply a vocabulary that describes objects and how they relate to one another.

A schema is a method for organizing information.

4. Agents  read all the metadata found at different sites.

Components of the Semantic Web(cont’d)

In our original example, we talked about buying "Star Wars" DVDs online. Here's how the Semantic Web could make the whole process easier:

Each site would have text and pictures (for people to read) and metadata (for computers to read) describing the DVDs available for purchase on their site.

The metadata, using RDF and XML tags, would make all the attributes of the DVDs (like condition and price) machine-readable.

When necessary, businesses would use ontologies to give the computer the vocabulary needed to describe all of these objects and their attributes. The shopping sites could all use the same ontologies, so all of the metadata would be in a common language.

Each site selling the DVDs would also use appropriate security and encryption measures to protect customers' information.

Computerized applications or agents would read all the metadata found at different sites. The applications could also compare information, verifying that the sources were accurate and trustworthy.

Tying it All Together

Semantic Web data is represented using a technology standard called Resource Description Framework (RDF).

RDF is a graph (web-like) structure that links data elements together in a self-describing way

Semantic Web Technologies

Supplemental components◦ Uniform Resource Identifiers (URIs)◦ Web services◦ Inference rules◦ Service discovery◦ Semantic aware applications◦ Security and trust◦ XML and RDF schemas

Supplemental Components of the Semantic Web

Semantic Web technology stack as a framework (the Semantic Web layer cake)

URI/IRI: URI is an acronym for Uniform Resource Identifier; a compact string of characters used to identify or name a resource. The URL to a web site (e.g. http://www.semanticfocus.com) is a popular example of a URI. IRI is an acronym for Internationalized Resource Identifier which is a form of URI that uses characters beyond ASCII, thus becoming more useful in an international context.

Unicode :Unicode is the universal standard encoding system and provides a unified system for representing textual data. 1 million characters can be encoded to specify any character in any language without a single escape sequence or control code. Before Unicode, there were several different encoding systems which made communication and integration across borders a big pain. (semanticfocus.com)

Semantic Web Foundations

XML: XML is an acronym for Extensible Markup Language. With XML, we have a standard way to compose information so that it can be more easily shared. At the same time, it still affords the freedom to structure that information however the heck we want. It's kind of like HTML - only, you get to make up your own tags and attributes. How cool is that?

Namespaces: Namespaces (aka XML Namespaces) are integral to XML. Namespaces provide a means to qualify the tags and attributes in an XML document with URIs which then makes them truly unique on the Web and thus, universal (among other things). (semanticfocus.com)

Semantic Web Foundations Cont’d

XML Schema XML Schema describes the structure of XML documents just like DTDs, only better. An XML Schema is known as an XML Schema Definition (XSD). Basically, if you're going to use XML to invent your own document structures, XSD provides the way to define your rules (like guidelines) so that people and machines can understand them, adhere to them, and integrate with them. XML

Query XML Query (aka XQuery) is a standardized language for combining documents, databases, Web pages and almost anything else. It is very widely implemented, powerful, and easy to learn. XQuery is replacing proprietary middleware languages and Web Application development languages. XQuery is replacing complex Java or C++ programs with a few lines of code. (semanticfocus.com)

Semantic Web Foundations Cont’d

RDF is a common framework for describing resources.

It is primarily intended to represent metadata that can be parsed and processed by machines rather than just displayed to people. While the resources it describes may be content or services that exist on the Web, they don't have to be; they can be real-world objects like you and I. Anything with identity can be described in RDF and, in this sense, RDF is a good candidate for recording and sharing knowledge on the Web

With RDF, we can model information by describing concepts in a way that is consistent enough for machines to process uniformly. (semanticfocus.com)

Semantic Web Foundations Cont’d

Ontology formally represents knowledge as a set of concepts within a domain, and the relationships among those concepts. It can be used to reason about the entities within that domain and may be used to describe the domain.

In theory, an ontology is a "formal, explicit specification of a shared conceptualization".[1] An ontology renders shared vocabulary and taxonomy which models a domain with the definition of objects and/or concepts and their properties and relations (wikipedia.org)

Semantic Web Foundations Cont’d

Provide the repositories for meaning interpretations

Provide a mechanism for defining the relationship among different words and for the Semantic Web, relationships among different resources

Ontologies

“the common words and concepts (the meaning) used to describe and represent an area of knowledge" (Daconta et al., 2003)

Consist of:◦ Taxonomies

“An organized set of terms.” (McComb, 2004) A classification and a tree (Daconta et al., 2003) Hierarchal, tree-like structures similar to

organizational charts Example

◦ Sets of inference rules Used to organize semantics

Ontologies (cont)

Next

Taxonomy Example

Back

Also known as software agents Provide automation services Should not be designed to replace humans

or to make decisions Examples: Web spiders and crawlers

Agents

scenario illustrates functionalities that can be implemented based on Semantic Web technologies

Agent (Cont)

Uniform Resource Identifiers (URIs)◦ Provide a mechanism for identifying available

resources ◦ The super-set of URNs, URLs and URCs

Web services◦ Allow computer applications to communicate

directly with each other over the Internet Inference rules

◦ Define the relationships and rules between data

Supplemental Components of the Semantic Web

Service discovery◦ Allows applications to find ontologies and agents

Semantic aware applications◦ Applications that can make use of semantic

information Security and trust XML schema

◦ Define the structure of XML documents◦ Standardizes the communication between

systems RDF schema or OWL

◦ Can be used to define the language used in ontologies and RDFs

Supplemental Components of the Semantic Web (cont)

Improve e-business processes Improve business-to-business (B2B)

communication “assist human users in their day-to-day

online activities” (Antoniou & van Harmelen, 2004)

“build knowledge and understanding from raw data” (Daconta et al., 2003)◦ Improve knowledge management◦ Improve information retrieval◦ Automate tasking◦ Integrate data◦ Maximize customer value and profits

Uses of the Semantic Web

Convert data to XML format according to defined XML schemas

Expose applications as Web services

Build ontologies that specify semantic meanings and the relationships between data

Create agents that make use of the semantic data, automate search processes, and automate other business processes

Implementing the Semantic Web

Cost Security Nonstandard technology issues Semantic precision

Issues Concerned with Implementing the Semantic Web

http://www.foaf-project.org/ http://www.cs.rpi.edu/~hendler/ http://www.mindswap.org/ http://www.daml.ri.cmu.edu/ http://www.semanticwebsearch.com/query/

Examples