Cogui, developed since 2005 and written in Java, is a graphical editor for building and checking knowledge bases.
Currently, it is devoted to conceptual graphs but it also imports/exports RDFS documents.
It can perform some reasoning tasks either alone or by communication with
Cogitant, evolving since 15 years and written in C++, is a platform for building conceptual graph applications.
This platform is a faithful implementation of the theoretical models developed in our team (see the Graph-based Knowledge Representation
book). Cogitant is now maintained by David Genest
KIABORA is an analyzer of rule bases dedicated to the existential rule framework
(see also Datalog+/-) written in Java. Its main purpose is to analyze decidability properties of a set of existential rules.
ALASKA (Abstract and Logic-based Architecture for Storage systems and Knowledge bases Analysis) is a generic Knowledge Representation architecture that uses an API that models a positive subset of First Order Logic. One can use it to load/parse data from RDF(S) or Datalog files, to store this information on disk using various systems, and to perform conjunctive queries over the stored content in a uniform way.
Written in Java, ALASKA is meant to work as the lower level component of any KR project.