We present a ke-based implementation of a reasoner for a decidable fragment of (stratified) set theory expressing the description logic $dlssx$ ($shdlssx$, for short). Our application solves the main TBox and ABox reasoning problems for $shdlssx$. In particular, it solves the consistency problem for $shdlssx$-knowledge bases represented in set-theoretic terms, and a generalization of the emph{Conjunctive Query Answering} problem in which conjunctive queries with variables of three sorts are admitted. The reasoner, which extends and optimizes a previous prototype for the consistency checking of $shdlssx$-knowledge bases (see cite{cilc17}), is implemented in textsf{C++}. It supports $shdlssx$-knowledge bases serialized in the OWL/XML format, and it admits also rules expressed in SWRL (Semantic Web Rule Language).