The School of Web Semantics Learning Semantic Web Techniques

When presenting a project, commercial or scientific, sooner or later you stumble upon the so-called elevator pitch, i.e., how to explain what we mean in just a few seconds.

Here's a story explaining why you should be interested in the Semantic Web.

Let us imagine that the leaders of Poland, Germany, Russia and the Czech Republic sit at one table to agree on the "historical truth" regarding the Second World War. What problems might they encounter?

1. They speak different languages.
2. Each nation has different "local" and often contradictory truths about that time.
3. The same places and events have different names.
4. The "objective" truth of those times is concealed deeply in the archives.

To address these problems, we want to enable correct and unconstrained exchange of knowledge between different systems.

The first step is to hire interpreters or to agree on a common language for this conversation; it is not hard to imagine that the representatives of these four countries will speak, e.g., English? This way, none of them will feel "cheated" by speaking the language of one of the participants in the meeting.

That is what RDF (Resource Desciption Framework) really is: a knowledge modeling language, which we will present shortly. Why not XML? ...

Second, each party sees the events of 70 years ago in a different way. And describes them using different formats. The same events, places, and words can have quite different connotations.

Therefore, XML is not a good idea - because to validate an XML document we need a common schema; while in RDF each party defines their own ontologies reusing a common vocabulary as often as possible. Submission of information from several sources does not require prior agreement on an ontology (the equivalent of an XML schema for RDF).

Third, besides having different meaning for historical places or events, each party may use different names. What we need is a common vocabulary, which will link various names for the same thing together.

This problem—linking different names for the same thing—can be solved with automation: common identifiers. While there is no way to force a single identifier for the same meaning, it is possible to figure out that different IDs point to the same concept. Rules found in an ontology, such as the inverse functional property, can be used with inference to uniquely identify a concept.

Last, but not least, an important part of the dialogue is to enable access to archives of all parties, without having to enter into separate bilateral agreements, independent visits to individual archives, etc.

Currently, the most important issue related to growing the global Semantic Web is to combine and provide an open access to various sources of knowledge (called Linked Open Data), such as blogs, wikis, open government data, etc. Only through enabling unified access to the global knowledge will Semantic Web really flourish.

This short example addresses a real problem not only on the Internet, but also in the real world. The Semantic Web is a global, distributed system, which (at least partially) helps (or will help) in solving such problems. So no wonder that President Obama's government decided to use Web 3.0 technologies to build the Recovery.gov portal.

In the next article we will describe how the idea of the Semantic Web was born.