The ways in RDFS to define RDF vocabularies are, with respect
their limited expressive power. That was a conscious decision
the design of RDFS. The language should be simple and understandable
be. However, the OWL is a language for describing ontologies
and thus more expressive than RDFS. Due to the OWL, such as
be integrated with RDFS, RDF knowledge bases. The language is a
Extension of RDFS with a larger number of functionalities to
To define class hierarchies and property restrictions.
These include relations between classes, cardinality (eg
"Exactly one"), equality, the more pronounced the possibilities of typing
Properties and property characteristics (eg symmetry).
To compromise between expressive power and efficient reasoning
permit, OWL has been divided into three languages. These three
Languages have different characteristics:
First OWL-Lite is a restricted form of OWL. It is optimized for
easy to understand and easy to implement to be. At
OWL-Lite are excluded disjoint expressions. Kardinalitätsbeschränkungen
are supported, but only the values
Allow 0 and 1. The disadvantage of 'simple' design of OWL-Lite
are limitations in the expressive power.
Second The OWL DL includes all the language features of OWL Full, but
partially restricted in their use are. OWL-DL is
for user oriented, need maximum expressiveness
and at the same time predictability (all conclusions are guaranteed predictable)
and decidability (all computations terminate in
finite time) are dependent.
Third OWL Full supports all language features of OWL and allows
an arbitrary combination of these characteristics with RDF and RDFS.
But this does: The flexibility comes at a price, at the expense of the
Decidability of reasoning goes.
The term "DL" in OWL-DL stands for Description Logics. This
form the formal basis for OWL. Description logics are a
Family of languages belonging to that used for knowledge representation
can be. Their origin is frame-based systems to
Knowledge representation. The concept was originally developed by Marvin Minsky
introduced.
A frame is a structure to represent a concept or a
Situation. Frames can be covered with different types of information
be. This includes information such as the definition, description
and use of frames. The description logics are important
Frame-based representation formalisms descendants, the declarative
Percentage of frames using a logic-based semantics
have taken over. As they are part of the first-order predicate logic
based and are decidable, they can hit on conclusions
can be (that is already present from new knowledge gained
be). In description logics, it is possible, a concept hierarchy
to build from atomic concepts and attributes. The attributes are
it usually referred to as roles. The intended meaning of
atomic concepts and role concepts can be other restrictions
be determined.
A simple example:
Woman = person and being female
Parent = person with a child
Grandmother = woman with a child, the parent is.
One of the most important tasks of reasoning in this context
The question is whether all instances of a concept necessarily
Other instances of the concept are. An answer to this question will
be found taking into account all definitions. Thus, for
Example, the "grandmother" as a "parent" classified, because each "grandmother"
by definition, also a "parent" is. Similar to the task
the classification is the task of reviewing authorities. Here
will determine the answer to the question whether a given object is an instance
the previously specified concept. Description logics,
as will become apparent, even to similarities in object-oriented concepts
Programming languages.
Thanks for writing such an easy-to-udnetrsand article on this topic.