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In-Depth Information
•
Data related to video files, films, and video production can be described using
VidOnt
, the
Video Ontology [78].
•
Geographic positions can be precisely annotated in
Geo
. It has the
lat
,
long
, and
alt
properties and the
SpatialThing
and
Point
classes [79].
Biographical information can be expressed by the
•
Bio
vocabulary [80].
•
In education, the IMS/IEEE
Learning Object Metadata
(
LOM
) can do a service [81].
•
Math-Net can be applied to standardize the presentation of information on mathematical
departments and research institutes [82].
•
People and their social networks can be precisely described in RDF/XML or OWL by Friend
of a Friend (FOAF) properties such as
name
,
homepage
,
knows
,
weblog
, and
interest
(see the
section “FOAF”) [83]. FOAF should be used on all social networking sites.
•
Professional capabilities and achievements can be described by Description of a Career
(DOAC) (see the section “DOAC”) [84]. DOAC is compatible with the European Curriculum
(Europass) that can be generated from a FOAF+DOAC file.
•
Software projects, in particular open source ones, can be expressed in Description of a Project
(DOAP) [85].
These schemas, vocabularies, and ontologies are just demonstrations for the endless variety. The list is not
complete by any means. VocabularyMarket [86],
vocab.org
[87], and other libraries collect further specific and
sophisticated vocabularies, schemas, and ontologies such as the Beer Ontology [88], the Music Vocabulary [89], or the
Music Ontology [90]. You can also find many vocabularies with a Google search.
Web ontologies have their limitations and open issues, however. For example, the verification of OWL ontologies
with rule extensions is rather complex. However, they can be verified at the symbolic level by using a declarative
approach (a new language called Datalog) [91]. The semantic differences between various ontologies should be
resolved. The effort to achieve that goal is known as
ontology alignment
. Storing and retrieving data from large RDFs
can be performed by advanced techniques only [92].
FOAF
FOAF is a machine-readable ontology to describe people and their contact data, interests, and relationships with
other people. In 2007, Berners-Lee defined a new Semantic Web concept known as the “Giant Global Graph”.
He stated that FOAF is an important part of the GGG: “I express my network in a FOAF file, and that is a start of the
revolution” [93].
Unlike conventional online social networks developed in PHP or JSP, FOAF networks can be built without a
centralized database. Additionally, FOAF content can be processed automatically. No one has to search for friends
in FOAF networks because the system itself describes the connections.
5
According to the original FOAF project started
in 2000, these systems are open networks [94].
There are more and more FOAF search engines, for example, QDOS FOAFNet [95], netEstate Friend Of A Friend
(FOAF) Search Engine [96], the Semantic Web Search [97], or Quatuo [98]. The latter one, for example, can also be
used for creating FOAF files. However, there are dedicated FOAF generators as well. The most well-known is
FOAF-O-MATIC developed by Leigh Dodds. FOAF files can be generated by filling in a form (Figure
7-2
) [99].
5
However, anybody can provide their own FOAF file and search for others'.
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