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DL theory distinguishes between concept and role definitions. Concepts basically represent unary predicates. Their relationship to other concepts is expressed with roles representing binary relations. Concepts are automatically classified with respect to subsumption relationships. The result of this process is a taxonomy of concepts. Higher-level nodes of this taxonomy represent more general concepts, leaves the most specialized ones. Another important notion are so-called number and value restrictions of roles. They restrict either the cardinality or the range of roles. DL systems support reasoning about these types of restrictions.
The translation to DL notation is not very difficult since we designed the specifications in a way that already resembles DL notation. This is illustrated with the definition of ports (repeated for the convenience of the reader):
The term `X:' expresses a number restriction (at most 1) for the role touching. The term PX constrains in this context the range of the role touching to members of the concept region. The result of this translation process is the following definition (using standard DL notation):