Everything that can be considered as a concept pattern Every class name is a concept pattern Every variable is a concept pattern A complement of a class name or variable is a concept pattern An intersection of concept patterns is a concept pattern \exists r.C where r is an object property and C is a concept pattern is a concept pattern \forall r.C where r is an object property and C is a concept pattern is a concept pattern Intuitively, the approximation of a concept description written in a DL L1 is a translation into a typically less expressive DL L2 with a minimal loss of information; There is an implementation of computing ALEN-approximations of ALCN-concept descriptions. This operation has two parameters: a concept description and a concept pattern; Roughly speaking, a concept pattern is a concept description where variables can appear at the places where concept names can appear in usual concept descriptions; Matching of a concept description C and a concept pattern D answers the question whether and how the variables in the concept pattern D can be assigned to concept descriptions such that a concept description is obtained that is equivalent with respect to a knowledge base to the concept description C. The Least Common Subsumer (LCS) of a set of concept descriptions is a concept description that subsumes all input concepts and is the least one with respect to subsumption to do so; The most expressive DL for which the LCS inference is currently available is ALEN. The Good Common Subsumer (GCS) of a set of concept descriptions is a concept description that subsumes all input concepts, but need not to be the least one with respect to subsumption; Furthermore, the implementation performs the computation with respect to a background terminology approach; This approach supports a (usually expressive) background terminology that is extended by the (usually not so expressive) user terminology; The most expressive DL for which the GCS is available is ALE user terminology with respect to an ALC background terminology. The minimal rewriting of a concept description C1 with respect to a terminology is a concept description C2, which is equivalent to C1 and of minimal size; Usually the minimal rewriting is obtained by replacing sub-concept descriptions by concept names form the terminology; In our implementation we realized a heuristic for minimal rewriting that returns a small, but not necessary the smallest rewriting for ALE concept descriptions. The machine name (IP address) where the DL-standard reasoner is running. The port where the DL-standard reasoner DIG 2.0 server is running. The knowledge base name where the TBox and ABox is stored.