10 semantic web & rdfa

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A paper on

SEMANTIC WEB & RDFa

Presented by

Siddhartha Gudipati Subhash Daggula B.Tech B.Tech

VRsiddhartha Engineering collegeVRsiddhartha Engineering college Email: [email protected]:[email protected]

Abstract

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In this paper we are going to introduce one of the

toughest problems that the web is facing today. Search

engines now a days depends and search only depending

on the key words. Humans are capable of using the Web

to carry out tasks such as finding the Finnish word for

"monkey", reserving a library book, and searching for alow price for 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 which is machine friendly and makes the

computer to know what the user wants. Once your

computer can understand a person a place and event days

it can help you interact with those things.

In this paper we are going to introduce the

semantic web concepts and how to implement it

using RDFa (Resource Description Framework) and

foaf(friend of a friend) vocabulary on your webpage.

So the Semantic Web makes our life easier by helping

computers helps us get what we want. However

Semantic Web technologies are still very much in

their infancies, and the future of the project in

general appears to be bright.

Semantics?

When I searched the dictionary for the meaning of

the word semantics I discovered that it is an adjective and

it meaning is as follows

1. Of or relating to meaning, especially meaning in

language.

2. Of, relating to, or according to the science of

semantics.

So Semantics is an adjective which gives the meaning of

something. Semantics is actually related to syntax. In

most languages syntax is how you say something.

Semantics is the meaning behind what you have said.

Lets take a phrase I Love technology as an example.

The syntax is all the letters, words, punctuation marks in

the sentence. The semantics is what the sentence actually

mean. In this case that means you enjoy learning about

and using new technology. Now if we would change the

sentence using different symbol for the word love we arechanging the sentence however note that the semantics of

the sentence still the same. When you write I

technology it still means that you enjoy learning and

using new technology.

The Internet

When we talk about the syntax and semantics what we

really talking about is communication when you want to

communicate with somebody else you use your voice to

do so. The internet created a standard way to

communicate with each other. In other words it gave a

voice to the computer so that they may talk to each other

and exchange information. However much like a parrot

mimic you and sounds without understanding them.

Computer nearly mimic the human information to one

another so while the internet enables computer to talk to

one another it was not designed to teach them what the

information actually means.

The Web

When the web came along and created a very

quick and easy way for us to retrieve and view

information. You can think web as a huge document

storage and retrieval system. When you put a website

address into your browser so it sends the request to a

website. The request basically states that you would likethe document located at the address that you gave. The

website retrieves the document and sends it back to your

web browser. This document is written in a language

called HTML. The html language that defines syntax that

computer can understand. It tell the computer how to

display the document to you so the two really needed

things that the web did is create a way to get any

document on the internet and also created a syntax called

html that is used to display the documents for you.

The Problem

Data that is generally hidden away in HTML

files is often useful in some contexts, but not in

others. The problem with the majority of data on the

web that is in this form at the moment is that it is

difficult to use on large scale, because there is no

global system for publishing data in such a way as it

can be easily processed by anyone. Technically

WWW means a set of protocols and languages driven

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by a strong standards approach namely URI, HTTP,

HTML, and HML. The principles involved are the

1) Implementation and platform independence crucial

and

2) World Wide Web consortium the most prominent.

Google Market Cap: 72.45 $

In comparison shopping also, the Market cap is

502.70$. Also in WWW who can you trust to send you e-mail

and how can we know for sure if a transaction really occurred.

So whats the big deal. We have the internet that talks to each

other we have the web that store and retrieve any documents

on the internet and the search engines which can find any of

the website that we want.

The web is already pretty good how we are going to

make it any better the answer lies in semantics. Remember

computer today just blindly retrieves and shows information

thats the problem. Computers dont understand the meaning

behind the WebPages that they are showing us. While they

may understand the syntax the semantics last on them. Now if

we can get computers to recognize what in a webpage they

could learn want they are interested in if they know that they

can help us get what we want. They would change passively

helping us to actively helping us.

About 3,660,000 Results were

returned....

A web of Things

This is what semantic web is all about it help the

computer understand the meaning behind the web page.

The web of today is about documents where as semantic

web is about things. When I say things I mean anything,

people, places, events, music, movies and just about any

concept that you think of. The semantic web is not only

about pointing things out to a computer but also about

letting computers know how this are related to each other.

There are several pouncing technologies that are in use

today that can embed semantics in a html document too

the more popular ways are called

1. Micro formats2. RDFa

RDFa

RDFa is based on RDF, RDF stands forResource Description Framework. Thats the fancy wayof saying that it can describe any concept relationship orthing that exists in the universe the idea RDF is sampleand it does very easy to grasp.

RDF has features that facilitate data mergingeven if the underlying schemas differ, and it specificallysupports the evolution of schemas over time withoutrequiring all the data consumers to be changed. RDFextends the linking structure of the Web to use URIs toname the relationship between things as well as the twoends of the link (this is usually referred to as a triple).Using this simple model, it allows structured and semi-structured data to be mixed, exposed, and shared acrossdifferent applications. This linking structure forms adirected, labelled graph, where the edges represent thenamed link between two resources, represented by thegraph nodes. This graph view is the easiest possible

mental model for RDF and is often used in easy-to-understand visual explanations.

There are three things in RDF subjects, predicates and objects. If you remember to yourelementary school English classes this should sound

pretty familiar to you the subject, object and predicateapproach how most western languages create basicsemantics. The subject refers to the thing you aredescribing the predicate usually refers to an attribute of athing that you are describing and the object is the thingwhich you are referring to with the predicate. Conceder a

basic example

Siddhartha likes sweets

In the above statement Siddhartha is the subject,likes is the predicate and sweets is the object. Using thissimple idea we can describe anything so that is basicallywhat RDF enables us to do.

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URI :( Uniform Resource Identifier)

RDF uses URIs to specify subjects andpredicates. URI stands for Uniform Resource Identifier.And is how we Identify things on the web. You're

probably already familiar with one form of URI: the URL

or Uniform Resource Locator. A URL is an address thatlets you visit a webpage, such as:http://www.w3.org/Addressing/. If you break

it down, you can see that a URL tells your computerwhere to find a specific resource (in this case, the W3C'sAddressing website). Unlike most other forms of URIs, aURL both identifies and locates. Contrast this with a"mid:" URI. A "mid:" URI identifies an email message,

but it isn't able to locate a copy of the message for you.

http://www.example.org/relly/long/urls/are/

hard/to/type/ect/

URI can be very long and annoying the type out.This is why we have a new concept in rdfa called curi.curis are a short hand ways of writing a long URI. curi isthe abbreviation of compact URI. An example of curi isfoaf:name.

In this case of curi foaf expands to a much linger URLand name is appended to the URL. You dont need toknow what URI means right now just the that the ting onthe left side of the colon expands to a long URL and thething on the right side of the colon is added to the end ofthe expanded URL.

Triples And N3 Notation

RDF and curis often come up when people talk

abou rdfa they are used when discussing rdf statements.Now rdf is a concept not a syntax so we must learn howto express rdf statements. This is where N3 notationcomes in. Remember that in RDF every thing is subject,

predicate, object statement. This statement is called triple.If we take out previous example Siddhartha like sweets

we can express it in N3 notation likes so.

@prefix pref:http://example.org/vocubular

.

The prefix line lets us know what the short hand is for allthe curies in the documents in other words it defines whatthe name spaces are moving to the next line we found the

actual triple the first item is subject and is enclosed inangle brackets to specify. The second item is the predicatewhich is also a URI fthe third Item is the object is also aURI, finally there is a period at the end of the triple to endthe statement. There can be many triples associated with a

particular subject the more triples there are the more we

know about the subject. If we look closely at this exampleyou will also notice that the predicate points to somethingcalled vocabulary.

The foaf vocabulary

Just like N3 is syntax used to describe RDF tohumans, Rdfa is a syntax used to describe RDF tocomputers. Neither N3 nor Rdfa have any inherit meaninguntil you pair them with vocabulary. The vocabularydefines what the triple actually means a vocabulary allowsa computer to understand when you are talking about a

specific concept. One such vocabulary that is quite popular on the semantic web is friend of a friendvocabulary also known as foaf. foaf contains severalconcepts that are useful for identifying people andrepresenting relationship those people foaf will be the firstvocabulary we use in this paper.

Creating a Triple

Using the foaf vocabulary it is easy to startdescribing someone on any web page all you need is URIthat talks about a person and a proper predicate todescribe that person. Lets use Siddhartha as a person letthe browser know whats his full name is. First we willneed to specify that we are going to use the foafvocabulary in our xhtml webpage. We do this by using anxmlns as an attribute, we will also need use two rdfaattributes about and property the first one is the aboutattribute and is used to set the subject and the second oneis the property attribute and is used to set the predicate.Finally we set his name using the text that will appear onthe webpage this is really helpful because whensomebody changes his name on the page perhaps to addmiddle initial they wont have to change anything else forthe machine readable part of the data to be updated. Both

the human readable and the machine readable rest comesfrom the exact same location on the page ensuring thatboth human and machine have most update data.

SiddharthaGudipati

Looking back over the example we define the namespace at

the top of the document we then set the subject using the about

attribute this followed by starting the predicate using a curi

which uses the namespace at the top of the document finallywe specify the object by rapping in the span element.

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http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/


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Any browser reading this webpage will know the Siddhartha

full name.

Types and Relationships

Now that the browser knows that there is

something with the name on the page we need to let it

know that Siddhartha is also a person to do this we can

use the instance of attribute. Instance of is used to specify

a type which is very special sort of attribute on a subject.

A type specifies exactly what class of thing the subject

falls into. In this case Siddhartha is a person foaf has a

class called person, so we apply using the instance of

attribute. Now the browser knows that Siddhartha is a

person. Lets go one step further and create a relationship.

SiddharthaGudipati

by stating that Siddhartha knows someone else on the

page named Rahul, to do this we setup another person on

the page named Rahul in the same way we setup

Siddhartha.

RahulKanna

Now all that is left to link them together to do this we use

the combination of the rel attribute and the resource

attribute there is a vocabulary term that foaf defines calledknows to state that one resource known another resource

we can use the foaf known as the predicate and link the

resource using rel.

SiddharthaGudipati

RahulKanna

Siddhartha is friends with Rahul

In this case we use recourse to target object forthe rel , Rahul could just easily as have been mentioned

on the another website and their remote website URL

could have been used instead of the local URL.

Building the Semantic Web

This is how the Semantic web is build. Triple by

triple, triple linked to other triples and which they linked

to more triples. These links go between pages, blogs, sites

and countries. The more triples that they are in the web

the more compute would be able to understand our world.This means that they will get really good helping us

finding news, music, people places and many more, that

what you are interested in.

The Possibilities

Things get really exciting when we start

exploring to explore the possibilities of the semantic web.

Once your computer understand a person a place and a

event days, it can help you interacting with those things

for example if a birthday party is marked up as an event

with a date and a place you can tell your computer to save

the date in your calander.

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Person

Siddharth

a gudipati

Siddhart

ha

Nam

Is

Siddhartha gudipati

Person

Siddharth

a Rahul

Rahul

khanna

Person

Know

NamNam

Is

Is
http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/


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Another example is in the world of music blogs, Music

blogs usually list songs and album reviews on their front

page. If the blog marked up the song in the artist semantic

web technology you can tell page to search the internet

for other albums by the same artist. Search engines would

also become a great deal more accurate than they aretoday. When you search you can search for any person,

place or any particular song. Search engine could then

refer to you a website with a far more accuracy, because it

wouldnt have just depend on keyword in WebPages any

more it could also depends on the semantics on the

webpage so that semantic web holds a great deal of proms

and making our lifes easier by helping computers help us

get what you want.

Semantic web Applications

Adobe uses RDF as a basis for documenting meta-data,

in PDF and other tools

Boeing uses RDF and OWL in several internal projects

AGFA uses RDF to categorize medical photos

NOKIA lots of Semantic Web activities. Including RDFknowledge store

IBM - Strong research activities

Conclusion

In coming days the web is going to change

because of the semantic web. The computers canunderstand what the user want give the information withfar more accuracy saving the time and money of the enduser. For some, the defining feature of the Semantic Webwill be the ease with which youre PDA, your laptop,your desktop, your server, and your car will communicatewith each other. For others, it will be the automation ofcorporate decisions that previously had to be laboriouslyhand-processed. For still others, it will be the ability toassess the trustworthiness of documents on the Web andthe remarkable ease with which we'll be able to find theanswers to our questions -- a process that is currentlyfraught with frustration.

Whatever the cause, almost everyone can find areason to support this grand vision of the Semantic Web.Sure, it's a long way from here to there -- and there be noguarantee we'll make it -- but we've made quite a bit of

progress so far. The possibilities are endless, and even ifwe don't ever achieve all of them, the journey will mostcertainly be its own reward.

References

[1].http://www.youtube.com/watch?v=OGg8A2zfWKg

[2].http://www.youtube.com/watch?v=ldl0m-5zLz4

[3]. http://www.w3.org/2001/sw/

[4].Semantic Web For Dummies March 2009 book by JefferyT. Pollock

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