Racer (intern)

Racer (Renamed ABox And Concept Expression Reasoner) 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 freely available, there are no network or runtime limitations. An open source version of Racer is available at Github.com. Racer can easily be installed via Quicklisp (http://quicklisp.org) with (ql:quickload "racer"). Note that Racer requires ASDF 2.32. This is relevant for Lispworks, for which also (setf asdf::*default-encoding* :default) should be evaluated.

Racer is distributed under the following BSD 3-clause license.

For downloading Racer as a server application, its APIs and documentation, just have a look at the section Download below.

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.


The standard way to download and install Racer is to use Quicklisp: (ql:quickload "racer").

An open source version of Racer 2.0 is available at Github.com

Racer has been tested with ACL 8.2, CCL 1.9, LW 6.1, and SBCL 1.4.




Selected publications

  • Volker Haarslev, Kay Hidde, Ralf Möller, and Michael Wessel. The RacerPro knowledge representation and reasoning system. Semantic Web Journal, 3(3):267–277, 2012.
    Bibtex entry  Paper (PDF)
  • M. Wessel and R. Möller. Flexible Software Architectures for Ontology-Based Information Systems. In Journal of Applied Logic, Special Issue on Empirically Successful Systems, 7(1): 75–99, 2009.
    Bibtex entry  Paper (PDF)
  • V. Haarslev and R. Möller. On the Scalability of Description Logic Instance Retrieval. Journal of Automated Reasoning, 41(2):99–142, 2008.
    Bibtex entry  Paper (PDF)
  • V. Haarslev and R. Möller. Racer System Description. In Proceedings of International Joint Conference on Automated Reasoning, IJCAR'2001: 701-705, Springer, 2001.
    Bibtex entry  Paper (PDF)


Prof. Dr. rer. nat. habil. Volker Haarslev
Concordia University
Department of Computer Science and Software Engineering
1455 de Maisonneuve Blvd. W.,
Montreal, Quebec  H3G 1M8,

Phone: +1 (514) 848-2424 ext. 3049
Email: haarslev -at- cse -dot- concordia -dot- ca


Prof. Dr. rer. nat. habil. Ralf Moeller
University of Luebeck
Institute of Information Systems
Ratzeburger Allee 160
23562 Luebeck

Phone: +49 (0)451 500 5700
Email: moeller@ifis.uni-luebeck.de


Dr. rer. nat. Michael Wessel
SRI International
333 Ravenswood Avenue
Menlo Park, CA 94025-3493

Phone: +1 (650) 859-4137
Email: michael.wessel@sri.com