Seminar on : Semantic WEB By: Vikas U. Abnave Roll no 301

WHAT IS SEMANTIC WEB ?

WHAT IS THE PURPOSE ?

To lead the World Wide Web to its full potential by developing protocols and guidelines that ensure long-term growth for the Web. —W3C, Mission The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web (W3). W3C has sixteen World Offices covering Australia, the Benelux countries (the Netherlands, Luxemburg, and Belgium), Mainland China, Finland, Germany and Austria, Greece, Hong Kong, Hungary, India, Ireland, Israel, Italy, Japan, South Korea, Korea, Morocco, Spain, Sweden, the United Kingdom and the United States.

W3C Semantic Web Layer Cake

XML provides a surface syntax for structured documents, but imposes no semantic constraints on the meaning of these documents. XML Schema is a language for restricting the structure and content elements of XML documents. RDF is a simple data model for referring to objects ("resources") and how they are related. An RDF-based model can be represented in XML syntax. OWL adds more vocabulary for describing properties and classes: among others, relations between classes

Uniform Resource Identifier (URI) A Uniform Resource Identifier (URI), is a compact string of characters used to identify or name a resource. For example, the URL http://www.wikipedia.org/ is a URI that identifies a resource (Wikipedia's home page) and implies that a representation of that resource (such as the home page's current HTML code, as encoded characters) is obtainable via HTTP from a network host named www.wikipedia.org.

Examples of absolute URIs Syntax "http", "ftp", "mailto", "urn", "mms", "rtsp", etc., followed by a colon character, and then a scheme-specific part. Examples of absolute URIs http://somehost/absolute/URI/with/absolute/path/to/resource.txt ftp://somehost/resource.txt urn:issn:1535- Examples of URI references http://example/resource.txt#frag01

Resource Description Framework (RDF) The RDF metadata model is based upon the idea of making statements about resources in the form of subject-predicate-object expressions, called triples in RDF terminology. Basic RDF Model Example: Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila.l

Figure 1: Simple node and arc diagram  Subject (Resource)   http://www.w3.org/Home/Lassila   Predicate (Property)   Creator  Object (literal)   "Ora Lassila" Figure 1: Simple node and arc diagram

Figure 2: Property with structured value

The RDF model for these sentences is: Figure 3: Structured value with identifier

Representation in RDF/XML as: <rdf:RDF> <rdf:Description about="http://www.w3.org/Home/Lassila"> <s:Creator>Ora Lassila</s:Creator> </rdf:Description> </rdf:RDF>

Applications 1. FOAF (Friend of a Friend) - designed to describe people, their interests and interconnections. 2. Many other RDF schemas are available by searching Schema Web

What is XML? XML stands for EXtensible Markup Language XML is a markup language much like HTML XML was designed to describe data XML tags are not predefined. You must define your own tags XML uses a Document Type Definition (DTD) or an XML Schema to describe the data XML with a DTD or XML Schema is designed to be self-descriptive XML is a W3C Recommendation XML is an extension from SGML. XML is extended to XHTML, RSS, Atom, ...

Features of XML XML can Separate Data from HTML With XML, your data is stored outside your HTML. 2. XML is Used to Exchange Data With XML, data can be exchanged between incompatible systems. 3. XML and B2B With XML, financial information can be exchanged over the Internet. 4. XML Can be Used to Share Data With XML, plain text files can be used to share data. 5. XML Can be Used to Store Data With XML, plain text files can be used to store data. 6. XML Can Make your Data More Useful With XML, your data is available to more users. 7. XML Can be Used to Create New Languages XML is the mother of WAP and WML.

Strengths of XML Weaknesses of XML Some features of XML that make it well-suited for data transfer are: It is simultaneously human and machine-readable format; It supports Unicode, allowing almost any information in any written human language to be communicated; The strict syntax and parsing requirements make the necessary parsing algorithms extremely simple, efficient, and consistent. XML is also heavily used as a format for document storage and processing, both online and offline, and offers several benefits: Its robust, logically-verifiable format is based on international standards; It is platform-independent, thus relatively immune to changes in technology; Weaknesses of XML Generic XML parsers must be able to recurse arbitrarily nested data structures and may perform additional checks to detect improperly formatted or differently ordered syntax or data Eg: Embedded Applications.

The XML Example Document Look at the following XML document ("cd_catalog.xml"), that represents a CD catalog: <?xml version="1.0" encoding="ISO-8859-1"?> <CATALOG> <CD> <TITLE>Empire Burlesque</TITLE> <ARTIST>Bob Dylan</ARTIST> <COUNTRY>USA</COUNTRY> <COMPANY>Columbia</COMPANY> <PRICE>10.90</PRICE> <YEAR>1985</YEAR> </CD> . more ....

XML was designed to carry data. The Main Difference Between XML and HTML XML was designed to carry data. XML is not a replacement for HTML. XML and HTML were designed with different goals: XML was designed to describe data and to focus on what data is. HTML was designed to display data and to focus on how data looks. HTML is about displaying information, while XML is about describing information. XML Does not DO Anything XML was not designed to DO anything. XML is Free and Extensible XML tags are not predefined. You must "invent" your own tags. XML is a Complement to HTML XML is not a replacement for HTML. XML is going to be everywhere.

Ontology Web Language (OWL) OWL is based on earlier languages OIL and DAML+OIL, and is now a W3C recommendation (i.e., a standard). OWL is written in XML. OWL was developed mainly because it has more facilities for expressing meaning and semantics than XML, RDF. History: W3c recommended OWL group in NOV 1,2001 by James Hendler.

Sublanguages : OWL Lite supports those users primarily needing a classification hierarchy and simple constraints. OWL DL supports those users who want the maximum expressiveness while retaining computational completeness and decidability. OWL Full is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees.

Future Scope ?

Security UNDER DEVELOPMENT

QUESTIONS ?