Social Networks and the SemanticWeb
As computing becomes ubiquitous and pervasive, computing is increasingly becoming
an extension of human, modifying or enhancing human experience. Today’s car
reacts to human perception of danger with a series of computers participating in how
to handle the vehicle for human command and environmental conditions. Proliferating
sensors help with observations, decision making as well as sensorymodifications.
The emergent semantic web will lead to machine understanding of data and help exploit
heterogeneous, multi-source digital media. Emerging applications in situation
monitoring and entertainment applications are resulting in development of experiential
The Semantic Web
The Semantic Web is the application of advanced knowledge technologies to the
Web and distributed systems in general.
But why would the Web need any extension or fixing? We will argue that the
reason we do not often raise this question is that we got used to the limitations of
accessing the vast information on the Web. We learned not to expect complete or
correct answers and not to ask certain questions at all.
In the following, we will demonstrate this effect on the example of some specific
queries (Section 1.1). What is common to these questions is that in all cases there
is a knowledge gap between the user and the computer: we are asking questions
that require a deeper understanding of the content of the Web on the part of our
computers or assume the existence of some background knowledge.As our machines
are lacking both our knowledge and our skills in interpreting content of all kinds
(text, images, video), the computer falls short of our expectations when it comes to
answering our queries.
Knowledge technologies from the field of Artificial Intelligence provide the necessary
means to fill the knowledge gap. Information that is missing or hard to access
for our machines can be made accessible using ontologies. As we will see in Section
4.1, ontologies are in part social, part technological solutions. On the one hand,
ontologies are formal, which allows a computer to emulate human ways of reasoning
with knowledge.On the other hand, ontologies carry a social commitment toward
using a set of concepts and relationships in an agreed way.
Limitations of the current Web
There is a general consent that the Web is one of the greatest inventions of the 20th
century. But could it be better?
The reason that we do not often raise this question any more has to do with our
unusual ability to adapt to the limitations of our information systems. In the case of
the Web this means adaptation to our primary interface to the vast information that
constitutes the Web: the search engine. In the following we list four questions that
search engines cannot answer at the moment with satisfaction or not at all.
What’s wrong with theWeb?
The questions below are specific for the sake of example, but they represent very
general categories of search tasks. As we will see later they also have in common that
in each of these cases semantic technology would drastically improve the computer’s
ability to give more appropriate answers (Section 1.2).
Who is Frank van Harmelen?
To answer such a question using theWeb one would go to the search engine and
enter the most logical keyword: harmelen. The results returned by Google are
shown in Figure 1.1. (Note that the results are slightly different depending on
whether one enters Google through the main site or a localized version.)
Find new music that I (might) like
This query is at an even higher level of difficulty so much so that most of us
wouldn’t even think of posing it to a search engine. First, from the perspective
of automation, music retrieval is just as problematic as image search. As in the
previous case, a search engine could avoid the problem of understanding the
content of music and look at the filename and the text of the web page for clues
about the performer or the genre. We suspect that such search engines do not
exist for different reasons: most music on the internet is shared illegally through
peer-to-peer systems that are completely out of reach for search engines. Music
is also a fast moving good; search engines typically index theWeb once a month
and therefore too slow for the fast moving world of music releases. (Google
News, the news search engine of Google addresses this problem by indexing
well-known news sources at a higher frequency than the rest of the Web.)
But the reason we would not attempt to pose this query mostly has to do with
formulating the music we like. Most likely we would search for the names of
our favorite bands or music styles as a proxy, e.g. “new release” (“Macy Gray”
OR “Robbie Williams”). This formulation is awkward on the one hand because
it forces us to query by example. It will not make it possible to find music that is
similar to the music that we like but from different artists. In other words it will
not lead us to discover new music.