Rei : A Policy Specification Language

April 1, 2002 - May 1, 2005

Security is a critical problem in dynamic and open distributed environments such as those enabled by the semantic web and pervasive computing technologies. The presence of heterogeneous entities that are neither pre-determined nor permanent, and the lack of central control are some of its challenges. We believe that declarative policies address this problem while maintaining openness and flexibility. We propose the use of policies defined in OWL to constrain the behavior of entities in these environments as OWL provides the extensibility required to incorporate varied application-specific knowledge.

Rei is a policy language based in OWL-Lite that allows policies to be specified as constraints over allowable and obligated actions on resources in the environment. Rei also includes logic-like variables giving it the flexibility to specify relations like role value maps that are not directly possible in OWL. Rei includes meta policy specifications for conflict resolution, speech acts for remote policy management and policy analysis specifications like what-if analysis and use-case management making it a suitable candidate for adaptable security in the environments under consideration. The Rei engine, developed in XSB, reasons over Rei policies and domain knowledge in RDF and OWL to provide answers about the current permissions and obligations of an entity, which are used to guide the entity's behavior.

confidentiality, owl, policy, privacy, rdf, rei, security, semantic web, speech acts, trust

OWL Tweet


  1. Mohinder Chopra, Trying to incorporate REI in the Task Computing project at Fujitsu Labs.
  2. Anjali Bharat Shah, Developing a GUI for Rei


  1. Anupam Joshi

Principal Investigator

  1. Lalana Kagal, Ph.D. Thesis



  1. L. Kagal, J. Parker, H. Chen, A. Joshi, and T. Finin, "Security, Privacy and Trust in Mobile Computing Environments", InBook, Handbook of Mobile Computing, Editors Imad Mahgoub and Mohammad Ilyas, December 2004, 3 citations.
  2. L. Kagal, T. Finin, and A. Joshi, "Declarative Policies for Describing Web Service Capabilities and Constraints", InProceedings, W3C Workshop on Constraints and Capabilities for Web Services, October 2004, 8606 downloads, 23 citations.
  3. A. Patwardhan, V. Korolev, L. Kagal, and A. Joshi, "Enforcing Policies in Pervasive Environments", InProceedings, International Conference on Mobile and Ubiquitous Systems: Networking and Services, August 2004, 5601 downloads, 30 citations.
  4. M. Cornwell, J. E. Just, L. Kagal, and T. Finin, "A Policy Based Collaboration Infrastructure for P2P Networking", InProceedings, Twelfth International Conference on Telecommunication Systems, Modeling and Analysis, July 2004, 2 citations.
  5. L. Kagal and T. Finin, "Modeling Conversation Policies using Permissions and Obligations", InProceedings, AAMAS 2004 Workshop on Agent Communication (AC2004), July 2004, 4991 downloads, 50 citations.
  6. L. Kagal, M. Paoucci, N. Srinivasan, G. Denker, T. Finin, and K. Sycara, "Authorization and Privacy for Semantic Web Services", Article, IEEE Intelligent Systems (Special Issue on Semantic Web Services), July 2004, 2832 downloads, 1 citation.
  7. M. Cornwell, J. E. Just, and L. Kagal, "Autonomic Policy-Based Collaboration for Cross-Agency Human Teams", InProceedings, Conference on the Human Impact and Application of Autonomic Computing Systems (CHIACS2), April 2004, 3799 downloads.
  8. L. Kagal, M. Paoucci, N. Srinivasan, G. Denker, T. Finin, and K. Sycara, "Authorization and Privacy for Semantic Web Services", InProceedings, First International Semantic Web Services Symposium, AAAI 2004 Spring Symposium, March 2004, 9517 downloads, 1 citation.


  1. F. Perich, A. Cedilnik, L. Kagal, and A. Joshi, "A Secure Infrastructure for Service Discovery and Access in Pervasive Computing", Article, ACM Monet: Special Issue on Security in Mobile Computing Environments, October 2003, 4482 downloads, 44 citations.
  2. G. Denker, L. Kagal, T. Finin, K. Sycara, and M. Paoucci, "Security for DAML Web Services: Annotation and Matchmaking", InProceedings, Second International Semantic Web Conference, September 2003, 4412 downloads, 125 citations.
  3. L. Kagal, T. Finin, and A. Joshi, "A Policy Based Approach to Security for the Semantic Web", InProceedings, 2nd International Semantic Web Conference (ISWC2003), September 2003, 11526 downloads, 218 citations.
  4. L. Kagal, T. Finin, and A. Joshi, "A Policy Language for A Pervasive Computing Environment", InCollection, IEEE 4th International Workshop on Policies for Distributed Systems and Networks, June 2003, 4989 downloads, 341 citations.


  1. L. Kagal, F. Perich, A. Joshi, and T. Finin, "A Security Architecture Based on Trust Management for Pervasive Computing Systems", InProceedings, Grace Hopper Celebration of Women in Computing, October 2002, 5646 downloads, 30 citations.
  2. L. Kagal, "Rei : A Policy Language for the Me-Centric Project", TechReport, HP Labs, September 2002, 4124 downloads.
  3. L. Kagal, F. Perich, A. Joshi, Y. Yesha, and T. Finin, "Vigil: Providing Trust for Enhanced Security in Pervasive Systems", TechReport, University of Maryland, Baltimore County, August 2002, 5413 downloads, 11 citations.
  4. L. Kagal, "An Agent Approach to Security for Pervasive Computing Environments", InProceedings, Doctoral Consortium, The Eighteenth National Conference on Artificial Intelligence (AAAI 02), July 2002.
  5. L. Kagal, T. Finin, and A. Joshi, "Developing Secure Agent Systems Using Delegation Based Trust Management", InProceedings, Security of Mobile Multi-Agent Systems Workshop, Autonomous Agents and Multiagent Systems (AAMAS 2002) , July 2002, 5412 downloads, 38 citations.


  1. L. Kagal, T. Finin, and A. Joshi, "Trust-Based Security in Pervasive Computing Environments", Article, IEEE Computer, December 2001, 9284 downloads, 214 citations.
  2. A. Cedilnik, L. Kagal, F. Perich, and A. Joshi, "A Secure Infrastructure for Service Discovery and Access in Pervasive Computing", TechReport, University of Maryland, Baltimore County, August 2001, 4450 downloads.
  3. L. Kagal, T. Finin, and Y. Peng, "A Delegation Based Model for Distributed Trust", InProceedings, Workshop on Autonomy, Delegation, and Control: Interacting with Autonomous Agents, International Joint Conferences on Artificial Intelligence, August 2001, 1211 downloads, 69 citations.
  4. L. Kagal, T. Finin, R. S. Cost, and Y. Peng, "A Framework for Distributed Trust Management", InProceedings, Second Workshop on Norms and Institutions in multi-agent systems, May 2001, 3860 downloads, 1 citation.