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Flora-2 is an open source semantic rule-based system for knowledge representation and reasoning. The language of the system is derived from F-logic,[1] HiLog,[2] and Transaction logic.[3] Being based on F-logic and HiLog implies that object-oriented syntax and higher-order representation are the major features of the system. Flora-2 also supports a form of defeasible reasoning called Logic Programming with Defaults and Argumentation Theories (LPDA).[4] Applications include intelligent agents, Semantic Web, knowledge-bases networking, ontology management, integration of information, security policy analysis, automated database normalization, and more.[5][6][7][8][9][10]

Flora-2 relies on the XSB system for its inference engine. The design and architecture of Flora-2 are described in a number of works.[11][12][13][14]

Details of the system and its use are described in the Flora-2 User's Manual.[15] Flora-2 is available for all major computing platforms, including Linux and other flavors of Unix, Microsoft Windows (both 32- and 64-bit), and Mac OS X.


Flora-2 is a successor to the Flora system (1998–1999) and incorporates the experience gained developing and using the original Flora system. The Flora-2 project started around year 2000 by Guizhen Yang and Michael Kifer. In later years it was led by Michael Kifer and had many other contributors.

Projects using Flora-2[edit]

  • TaOPiS is a social semantic Web application for supporting self-organizing communities.[16][17][18]
  • Baze is a database development environment similar to Access and Base.
  • ReasonablePython is a module which adds F-Logic to Python.[19]
  • The FRDCSA project is developing an extension to the Perl XSB interface for supporting access to Flora-2 and HiLog from Perl and the FreeKBS3 system.


  1. ^ M. Kifer, G. Lausen, J. Wu (1995). Foundations of Object-Oriented and Frame-Based Languages, Journal of ACM, May 1995.
  2. ^ W. Chen, M. Kifer and D.S. Warren (1993), HiLog: A Foundation for Higher-Order Logic Programming. Journal of Logic Programming, 1993.
  3. ^ A.J. Bonner and M. Kifer (1993), Transaction Logic Programming, International Conference on Logic Programming (ICLP), 1993.
  4. ^ H. Wan , B. Grosof , M. Kifer , P. Fodor , S. Liang (2009), Logic Programming with Defaults and Argumentation Theories. 25th International Conference on Logic Programming (ICLP 2009), July 2009.
  5. ^ H. Chen, T. Finin, and A. Joshi (2003). An ontology for context-aware pervasive computing environments, The Knowledge Engineering Review 18:3, Cambridge University Press.
  6. ^ Y. Zou, T. Finin, H. Chen (2005). F-OWL: An Inference Engine for Semantic Web, Formal Approaches to Agent-Based Systems, Lecture Notes in Computer Science v. 3228, Springer Verlag.
  7. ^ A. D. Lattner , J. D. Gehrke , I. J. Timm , O. Herzog (2005) A knowledge-based approach to behavior decision in intelligent vehicles, Intelligent Vehicles Symposium, IEEE, pp. 466-471.
  8. ^ M. Malekovic and M. Schatten (2008) Leadership in Team Based Knowledge Management - An Autopoietic Information System's Perspective, Central European Conference on Information and Intelligent Systems (CECIIS-2008), University of Zagreb.
  9. ^ T. Orehovacki, M. Schatten, A. Lovrencic (2011) Implementing a Logic System for Testing Functional Independent Normal Form in Relational Databases, Proceedings of the 33rd International Conference on Information Technology Interfaces / Lužar-Stiffler, Vesna ; Jarec, Iva ; Bekić, Zoran (ed). - Zagreb : University Computing Centre, University of Zagreb , 2011. 167-172 (ISBN 978-953-7138-20-2).
  10. ^ M. Schatten (2013) Knowledge Management in Semantic Social Networks, Computational & Mathematical Organization Theory (1381-298X) 19, 4; 538-568
  11. ^ G. Yang and M. Kifer (2000), Flora: Implementing an Efficient DOOD System Using a Tabling Logic Engine. Intl. Conference on Computational Logic, July 2000.
  12. ^ G. Yang, Michael Kifer, and C. Zhao (2003), FLORA-2: A Rule-Based Knowledge Representation and Inference Infrastructure for the Semantic Web. Second International Conference on Ontologies, Databases and Applications of Semantics (ODBASE), Catania, Sicily, Italy, November 2003.
  13. ^ M. Kifer (2005), Nonmonotonic reasoning in Flora-2. Int'l Conf. on Logic Programming and Nonmonotonic Reasoning. Lecture Notes in Computer Science Volume 3662, 2005, pp 1-12.
  14. ^ G. Yang and M. Kifer (2003), Reasoning about Anonymous Resources and Meta Statements on the Semantic Web. Journal on Data Semantics. Lecture Notes in Computer Science vol. 2800, Springer, 2003.
  15. ^ M. Kifer, G. Yang, H. Wan, C. Zhao (2013),Flora-2 User's Manual
  16. ^ M. Schatten, M. Cubrilo, J.Seva (2008) A Semantic Wiki System Based on F-Logic, Central European Conference on Information and Intelligent Systems (CECIIS-2008), University of Zagreb.
  17. ^ M. Schatten, M. Cubrilo, J.Seva (2009) Dynamic Queries in Semantic Wiki Systems, Central European Conference on Information and Intelligent Systems (CECIIS-2009), University of Zagreb.
  18. ^ M. Schatten, V. Kakulapati, M. Cubrilo (2010) Reasoning about Social Semantic Web Applications using String Similarity and Frame Logic, Central European Conference on Information and Intelligent Systems (CECIIS-2010), University of Zagreb.
  19. ^ M. Schatten (2007) Reasonable Python or how to Integrate F-Logic into an Object-Oriented Scripting Language, Intelligent Engineering Systems (INES-2007), IEEE, pp. 297-300.

External links[edit]