Where it all started: The semantic web according to Berners-Lee

There is no study about the semantic web that can’t include the very paper of Berners-Lee et al. published May 2001 in Scientific American. In there they presented the semantic web as a new form of web content meaningful to computers. They believed and today still do that it will unleash a revolution of new possibilities.In this article the authors started immediately with an example of the scheduling of an appointment of two busy persons. They both used the help of  their ‘agents’. Those agents were able to help them thanks to a concept called the Semantic Web.  It differs from the World Wide Web in the sense that it will bring structure to the meaningful content of Web pages, creating an environment where software agents roaming from page to page can readily carry out sophisticated tasks for users. According to the authors the Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation. Like the Internet, the Semantic Web will be as decentralized as possible.

For the semantic web to function, computers must have access to structured collections of information and sets of inference rules that they can use to conduct automated reasoning. They compared the semantic web with knowledge representation systems studied by artificial intelligence researchers. But for the semantic web to realize its full potential it must be linked into a single global system. A very important difference with traditional knowledge-representation systems is that they generally each had their own narrow set of rules and could only answer questions fully reliable or not at all. Semantic Web researchers, in contrast, accept that paradoxes and unanswerable questions are a price that must be paid to achieve versatility. Berners-Lee et al. noted that in the conventional web, detractors also pointed out that the conventional web could never be like an organized library. One would never be sure of finding everything and so it turned out to be.  Projecting this on the semantic web leaded to a challenge. It  is to provide a language that expresses both data and rules for reasoning about the data and that allows rules from any existing knowledge-representation system to be exported onto the Web.

Two important technologies for developing the Semantic Web were at the time of writing already in place: eXtensible Markup Language (XML) and the Resource Description Framework (RDF). XML allows users to add arbitrary structure to their documents but says nothing about what the structures mean. Meaning is expressed by RDF, which encodes it in sets of triples, each triple being rather like the subject, verb and object of an elementary sentence. These triples can be written using XML tags. They continued then with a description of RDF and the roles URI’s have in it. The authors emphasized that the Semantic Web will enable machines to comprehend semantic documents and data, not human speech and writings.

That was not the end of the story. Two databases may use different identifiers for what is in fact the same concept. A solution to this problem is provided by the third basic component of the Semantic Web, collections of information called ontologies. The most typical kind of ontology for the Web has a taxonomy and a set of inference rules. Then some examples explained this in more detail. With ontology pages on the Web, solutions to terminology (and other) problems begin to emerge. The meaning of terms or XML codes used on a Web page can be defined by pointers from the page to an ontology. Ontologies can enhance the functioning of the Web in many ways. They can be used in a simple fashion to improve the accuracy of Web searches—the search program can look for only those pages that refer to a precise concept instead of all the ones using ambiguous keywords. More advanced applications will use ontologies to relate the information on a page to the associated knowledge structures and inference rules.

Berners-Lee et al. focused also on the concept of agents. 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 promotes this synergy: even agents that were not expressly designed to work together can transfer data among themselves when the data come with semantics. They continued by highlighting other aspects of the agents such as digital signatures and exchange of proofs. Putting all these features together results in the abilities exhibited in the example that opened this article, concluded the authors. The idea is that the agents delegate a task to other services discovered through service advertisements. These activities formed chains in which a large amount of data distributed across the Web (and almost worthless in that form) was progressively reduced to the small amount of data of high value the agent can then return. According to the others it doesn’t end there.

In the next step, the Semantic Web will break out of the virtual realm and extend into our physical world. URIs can point to anything, including physical entities, which means we can use the RDF language to describe all kind of devices. The authors presented some applications to illustrate this idea. In 2001, the first concrete steps have already been taken in this area, with work on developing a standard for describing functional capabilities of devices. Berners-Lee et al. pushed it even further. The semantic web should not “merely” be the tool for conducting individual tasks that they had discussed so far. In addition, if properly designed, the Semantic Web could assist the evolution of human knowledge as a whole. They continued by explaining themeselves: a small group can innovate rapidly and efficiently, but this produces a subculture whose concepts are not understood by others. An essential process is the joining together of subcultures when a wider common language is needed. Often two groups independently develop very similar concepts, and describing the relation between them brings great benefits. Berners-Lee at all concluded that the Semantic Web, in naming every concept simply by a URI, lets anyone express new concepts that they invent with minimal effort. Its unifying logical language will enable these concepts to be progressively linked into a universal Web. This structure will open up the knowledge and workings of humankind to meaningful analysis by software agents, providing a new class of tools by which we can live, work and learn together.

Lee et al. The semantic web. Scientific American (2001)


About laurensdv
Computer Science Student, interested in creating more innovating user experiences for information access. Fond of travelling around Europe!

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