The World Wide Web is an interesting paradox – it ’s made with computers but for people . The sites you confabulate every day utilise natural language , persona and varlet layout to present information in a way that ’s easy for you to empathize . Even though they are central to make and maintain the Web , the computer themselves really ca n’t make horse sense of all this info . They ca n’t read , see relationships or make decisions like you may .
TheSemanticWeb proposes to aid computers " read " and use the entanglement . The self-aggrandizing idea is passably round-eyed –metadataadded to connection pages can make the existing World Wide entanglement car clear . This wo n’t bestow artificial intelligence or make computers self - aware , but it will give machine tool to find , exchange and , to a special extent , interpret entropy . It ’s an extension of , not a permutation for , the World Wide WWW .
That probably sound a petty abstract , and it is . While some land site are already using Semantic Web concepts , a lot of the necessary shaft are still in developing . In this article , we ’ll bring the concepts and tools behind the Semantic WWW down to earth by applying them to a galaxy far , far away .
Why Semantic Web?
Suppose you want to purchase a " Star Wars Trilogy " boxed set online , and you have some introductory touchstone for your purchase . First , you want widescreen , not full - concealment , videodisk , and you want the set that has the extra disc of bonus material . Second , you need the low available damage , but you ’d choose to grease one’s palms a newfangled bent , not a used one . Finally , you do n’t require to compensate too much for transportation and manipulation , but you also do n’t require to wait too farsighted for delivery .
At this point in the evolution of the connection , your best bet would be to count at unlike retailer ' web pages , comparing price and shipping time and rate . You could also seem for a internet site that will liken price and merchant vessels options from several retailers all at once . Either way , you have to do most of the virtual legwork , then make your buying decisiveness and grade your social club yourself .
With the Semantic Web , you ’d have another option . You could come in your preferences into a computerizedagent , which would look the Web , encounter the best option for you , and place your order . The broker could then open personal finance software on your computer and record the amount you pass , and it could mark the date your DVDs should arrive on your calendar . Your agent would also learn your habits and preferences , so if you had a bad experience purchase from one particular situation it would know not to use that situation again .
The agent would do this not by looking at pictures and reading descriptions like a individual does , but by searching throughmetadatathat intelligibly identify and define what the agent needs to know . Metadata are only machine - readable data point that describe other data point . In the Semantic Web , metadata are invisible as the great unwashed scan the page , but they ’re clearly seeable to electronic computer . Metadata can also reserve more complex , focussed WWW search with more accurate resultant role . To paraphrase Tim Berners - Lee , artificer of the World Wide connection , these tool will rent the WWW – currently exchangeable to a giant book – become a giant database .
We ’ll count at the tools that can make documents machine readable next .
Marking Up: XML and RDF
Let ’s say you want to make this sentence decipherable to a computer :
Anakin Skywalker is Luke Skywalker’s father.
It ’s easy for you to figure out what this condemnation means – Anakin and Luke Skywalker are both people , and there is a family relationship between them . You know that a father is a type of parent , and that the sentence also intend that Luke is Anakin ’s son . But a computer ca n’t figure any of that out without help . To tolerate a computer to realise what this sentence have in mind , you ’d need to append machine - decipherable information that describes who Anakin and Luke are and what their relationship is . This starts with two tools –eXtensible Markup Language ( XML)andResource Description Framework ( RDF ) .
XML is amarkup languagelikehypertext markup language ( HTML ) , which you ’re probably more or less intimate with from surfing the Web . HTML governs the show of the information you look at on the Web . XML complements ( but does not replace ) HTML by addingtagsthat describe data point . These tags are unseeable to the people who register the document but seeable to computer . Tags are already in use on the Web , and existingbots , like the bot that pull together data forsearch engines , can read them .
RDF does on the button what its name argue – using XML tags , it offer a framework to describeresources . In RDF terms , passably much everything in the world is a resource . This theoretical account pairs the resource ( any noun , like Anakin Skywalker or the " Star Wars " trilogy ) with a specific item or location on the entanglement so the computing gadget knows exactly what the resource is . clear identifying resources keeps the data processor from doing things like confusing Anakin Skywalker with Sebastian Shaw or Hayden Christiansen , or the original trilogy with the One - Man " Star Wars " Trilogy .
To do this , RDF usestripleswritten as XML tags to express this entropy as agraph . These trio consist of asubject , propertyandobject , which are like the subject , verb and direct objective of a sentence . ( Some sources call these the subject area , predicate and objective . ) RDF already exist on the World Wide Web – for example , it ’s part of RSS provender creation .
So far in this example , the computing machine recognise that there are two target in this sentence and that there is a relationship between them . But it does n’t roll in the hay what the objects are or how they relate to one another . We ’ll take care at the shaft for adding this stratum of meaning next .
Knowing What’s What: URIs
Even with the framework that XML and RDF provide , a computer still needs a very direct , specific way of agreement who or what these resources are . To do this , RDF usesuniform imagination identifier ( URIs)to direct the computing machine to a text file or physical object that represent the resourcefulness . You ’re already conversant with the most common form of URI – the uniform resource locator ( universal resource locator ) , which start withhttp://. A URI can level to anything on the Web and may also luff to object that are not part of the entanglement , like appliances in computerized homes . Mailto , ftp and telnet reference are some other representative of URIs .
For our example , we ’ll practice the characters ' pages at the prescribed Star Wars site as their URIs .
Now the computer knows what the subject and aim are – Anakin Skywalker is the entity represented by the first URI , and Luke Skywalker is the entity present by the second . But you ’ll mark that the middle URI in our threefold – the one for the property – does n’t point to the Star Wars site . or else , it points to a make - believe document on the HowStuffWorks server . If that page really existed , it would be ourXML namespace .
Unlike HTML , which uses stock tags like < b > for bold and < u > for underscore , XML does n’t have standard tags . This is useful – it lease developers create unique tags for specific purposes . But it means that a internet browser does n’t automatically know what the tags mean . An XML namespace is fundamentally a document that tells applications the meaning of all the tags in another document . The creator of an XML papers declares the namespace at the beginning of the document with a line of code . In our model , our namespace announcement would look like this :
< rdf : RDF xmlns : hsw = https://www.howstuffworks.com / example / RDF / relationship # >
That line of codification says to the computing machine , " Any tag you see that begin with ' hsw ' use the vocabulary found in this document . you’re able to look up any tag beginning with ' hsw ' here . " That way , people can create the XML tag end they need for a document without conflicting with other XML documents on the Web .
XML and RDF are the " official spoken communication " of the Semantic Web , but by themselves they ’re not enough to make the intact Web accessible to a computer . We ’ll look at some of the other layer next .
Languages and Vocabularies:RDFS, OWL and SKOS
Another obstacle for the Semantic Web is that information processing system do n’t have the kind of vocabulary that hoi polloi do . You ’ve used language your whole life , so it ’s in all likelihood easy for you to see connections between unlike word of honor and concept and to infer meanings found on contexts . regrettably , someone ca n’t just give a reckoner a dictionary , an almanac and a set of encyclopedias and let the computer learn all this on its own . for read what words think and what the relationships between words are , the reckoner has to havedocumentsthat describe all the intelligence andlogicto make the necessary connections .
In the Semantic Web , this comes fromschemataandontologies . These are two related tools for helping a computer translate human lexicon . An ontology is plainly a vocabulary that account objects and how they relate to one another . A schema is a method acting for organizing info . As with RDF tags , access to schemata and ontology are included in written document as metadata , and a papers ’s creator must adjudge which ontology are referenced at the beginning of the written document .
Schema and ontology tools used on the Semantic Web include :
The trouble with ontologies is that they are very difficult to create , implement and keep . reckon on their scope , they can be enormous , delimitate a wide mountain chain of concepts and relationship . Some developers choose to focus more on logical system and formula than on ontologies because of these difficultness . Disagreements regarding the roles these rules should wager may be one possible pitfall for the Semantic Web .
Next , we ’ll tie it all together by looking at our original example – those " Star Wars Trilogy " DVDs .
Tying it All Together
In our original exemplar , we talked about buy " Star Wars " videodisc online . Here ’s how the Semantic Web could make the whole process sluttish :
Of course , the Web is enormous , and add all this metadata to existing Sir Frederick Handley Page is a immense undertaking . We ’ll see at this and some of the other likely hurdles for the Semantic vane next .
W3C and the Future of the Semantic Web
Like the World Wide Web , the Semantic Web isdecentralized– no one organisation or agency has command over all of its rules and content . However , some people and organizations have lead leaders roles in the development of Semantic World Wide Web guideline and protocols . These include the World Wide Web Consortium ( W3C ) , its conductor Tim Berners - Lee and its extremity organizations . The W3C is not a inquiry organization , so universities , other organisation and the public also play an participating role in Semantic Web development .
Some area of the World Wide vane have already incorporated Semantic connection part . These include RSS feeds , which use RDF , and the Friend - of - a - Friend ( FOAF ) projection , which proposes to make car - readable personal World Wide Web pages .
But much of the Semantic Web ’s social function and practicality are still in development , and there are some pretty big obstruction to overpower . decentalisation gives developers the freedom to create just the tag and ontologies that they need . But , it also means that different developers might use dissimilar tag to describe the same thing , which could make machine comparisons difficult . Critics also interview the " individuality job " – does a URI map a Web page , or does it represent the concept or object the page describes . For example , is " http://www.starwars.com " have in mind to represent the " Star Wars " films , or just the Web Sir Frederick Handley Page ?
Some developers disagree on whether the Semantic Web should rely more heavily on rules or on ontology . Critics also say that the project is enormously impractical . First , people do n’t actually think in terms of the graph that RDF uses . Second , it seems improbable that businesses and existing sites will actually devote the time and resourcefulness it would take to add all the necessary metadata . In the hereafter , off - the - shelf software might include options for adding metadata when create novel documents , but that creature still might not make the labor viable on a larger scale .
For lots more entropy on the World Wide Web and the Semantic Web , check out the radio link on the next pageboy .
