Racer is a knowledge representation system that implements a highly optimized tableau calculus for the description logic SRIQ(D).
Racer is the successor of the previous RacerPro system. For those of you who used the previous web site it is important to note that Racer is now freeware. Downloadable server systems come as freeware with no license files, no license fees, and there are no network or runtime limitations. An open source version of Racer will be released really soon now with some version of the BSD licensing model. Racer is distributed under the following BSD 3-clause license.
For downloading Racer, its APIs and documentation, just click the download tab.
Racer provides implementations of standard reasoning problems for T-boxes and A-boxes. In addition, some non-standard inference services are provided, such as, e.g., logical abduction. Racer also provides the powerful and semantically well-defined conjunctive query language nRQL (new Racer Query Language, to be pronounced as niracle and heard as miracle), which also supports negation as failure, numeric constraints w.r.t. attribute values of different individuals, substring properties between string attributes, etc. It has convenient APIs for accessing its reasoning services from within Common Lisp and Java.