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Distributed Evaluation of Network Directory Queries
April 2004 (vol. 16 no. 4)
pp. 474-486
Sihem Amer-Yahia, IEEE Computer Society
Divesh Srivastava, IEEE Computer Society

Abstract—This paper describes novel efficient techniques for the distributed evaluation of hierarchical aggregate selection queries over LDAP directory data, distributed across multiple autonomous directory servers. Such queries are useful for emerging applications like the Directory Enabled Networks initiative. Our techniques follow the LDAP approach of distributed query evaluation by referrals, where each relevant server computes answers locally, and the LDAP client coordinates between directory servers. We make a conceptual separation between the identification of relevant servers and the distributed computation of answers. We focus on the challenging task of generating an efficient plan for evaluating hierarchical aggregate selection queries, which involves correlating directory entries across multiple servers. The key features of our plan are: 1) the network traffic consists of query answers, and auxiliary messages that depend only on the number of servers and the size of the query (not on the data size), 2) the coordination effort at the client is independent of the data size, and 3) potentially expensive server-to-server communication and coordination is avoided. We complement our analysis with experiments that show the robustness and scalability of our techniques for highly distributed directory query processing.

[1] Directory Enabled Networks Ad Hoc Working Group,http://www.murchiso.comden/, 2003.
[2] Open LDAP: Community Developed LDAP Software, available fromhttp:/, 2003.
[3] P.A. Bernstein and N. Goodman, Power of Natural Semijoins SIAM J. Computing, vol. 10, no. 4, pp. 751-771, Nov. 1981.
[4] R. Chaudhury, E. Ellesson, S. Kamat, J.-C. Martin, G. Powers, R. Rajan, D. Verma, and R. Yavatkar, Directory Schema for Service Level Administration of Differentiated Services and Integrated Services in Networks draft submitted to Directory Enabled Networks Ad Hoc Working Group, available from den-draft-ellesson-sla-schema-02.txt , 1998.
[5] T. Howes and M. Smith, LDAP: Programming Directory-Enabled Applications with Lightweight Directory Access Protocol. Indianapolis, Ind.: Macmillan Technical Publishing, 1997.
[6] T. Howes, M. Smith, and G.S. Good, Understanding and Deploying LDAP Directory Services. Indianapolis, Ind.: Macmillan Technical Publishing, 1999.
[7] H.V. Jagadish, L.V.S. Lakshmanan, T. Milo, D. Srivastava, and D. Vista, Querying Network Directories Proc. ACM SIGMOD Conf. Management of Data, pp. 133-144, June 1999.
[8] D. Kossman, The State of the Art in Distributed Query Processing ACM Computing Surveys, vol. 32, no. 4, pp. 422-469, 2000.
[9] J.K. Mullin, “Optimal Semijoins for Distributed Database Systems,” IEEE Trans. Software Eng., vol. 16, no. 5, pp. 558-560, May 1990.
[10] M.T. Ozsu and P. Valduriez, Principles of Distributed Database Systems. Prentice Hall, 1991.
[11] J. Strassner, Directory Enabled Networks. Indianapolis, Ind.: Macmillan Technical Publishing, 1999.
[12] M. Wahl, T. Howes, and S. Kille, Lightweight Directory Access Protocol (v3) Request for Comments 2251, available from, Dec. 1997.

Index Terms:
LDAP directories, hierarchical aggregate selection, distributed query evaluation, aggregate value cache, topology identification.
Sihem Amer-Yahia, Divesh Srivastava, Dan Suciu, "Distributed Evaluation of Network Directory Queries," IEEE Transactions on Knowledge and Data Engineering, vol. 16, no. 4, pp. 474-486, April 2004, doi:10.1109/TKDE.2004.1269671
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