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A Graph-Based Data Model and its Ramifications
October 1995 (vol. 7 no. 5)
pp. 809-823

Abstract—Currently, database researchers are investigating new data models in order to remedy the deficiences of the flat relational model when applied to nonbusiness applications. Herein we concentrate on a recent graph-based data model called the hypernode model. The single underlying data structure of this model is the hypernode which is a digraph with a unique defining label. We present in detail the three components of the model, namely its data structure, the hypernode, its query and update language, called HNQL, and its provision for enforcing integrity constraints. We first demonstrate that the said data model is a natural candidate for formalising hypertext. We then compare it with other graph-based data models and with set-based data models. We also investigate the expressive power of HNQL. Finally, using the hypernode model as a paradigm for graph-based data modelling, we show how to bridge the gap between graph-based and set-based data models, and at what computational cost this can be done.

[1] S. Abiteboul and P.C. Kanellakis,“Object identity as a query language primitive,” Proc. 1989 ACM SIGMOD Int’l Conf. the Management of Data, SIGMOD Record, vol. 18, no. 2, pp. 159-173, June 1989.
[2] S. Abiteboul and V. Vianu, "Procedural Languages for Database Queries and Updates, J. Computer and System Sciences, vol. 41, no. 2, pp. 181-229, Oct. 1990.
[3] P. Aczel,Non-well-founded Sets, Lecture Notes No. 14. Stanford, Calif.: Center for the Study of Language and Information (CSLI), 1988.
[4] J. Barwise and L. Moss,“Hypersets,” The Mathematical Intelligencer, vol. 13, pp. 31-41, 1991.
[5] F. Buckley and F. Harary,Distance in Graphs.Redwood City, Calif.: Addison-Wesley, 1990.
[6] A.K. Chandra and D. Harel,“Computable queries for relational data bases,” J. Computer and System Sciences, vol. 21, pp. 156-178, 1980.
[7] A.K. Chandra, "Theory of Database Queries," Proc. PODS-88, 1988.
[8] P.P. Chen, “The Entity‐Relationship Model: Toward a Unified View of Data,” ACM Trans. Database Systems, Vol. 1, No. 1, Jan. 1976, pp. 9–36.
[9] W.F. Clocksin and C.S. Mellish,Programming in Prolog, 2nd ed. New York: Springer-Verlag, 1984.
[10] N. Coburn and G.E. Weddell,“Path constraints for graph-based data models: Towards a unified theory oftyping constraints, equations and functional dependencies,” Proc. Int’l Conf. Deductive and Object-Oriented Databases,Munich, Germany, pp. 312-331, 1991.
[11] E.F. Codd,“A relational model of data for large shared data banks,” Comm. ACM, vol. 13, no. 6, June 1970.
[12] E. Codd,“Extending the database relational model to capture more meaning,” ACM Trans. Database Systems, vol. 4, no. 4, pp. 397-434, 1979.
[13] J. Conklin, “Hypertext: A Survey and Introduction,” Computer, Vol. 20, No. 9, Sept. 1987, pp. 17-41.
[14] M.P. Consens and A.O. Mendelzon,“Expressing structural hypertext queries in Graphlog,” Proc. ACM Conf. Hypertext, Pittsburgh, Pa., pp. 269-292, 1989.
[15] M.P. Consens and A.O. Mendelzon,“GraphLog: A visual formalism for real life recursion,” Proc. Ninth ACM Symp. Principles of Database Systems, pp. 404-416, Apr. 1990.
[16] S.J. DeRose,“Expanding the notion of links,” Proc. ACM Conf. Hypertext,Pittsburgh, Pa., pp. 249-257, 1989.
[17] M.R. Garey and D.S. Johnson, Computers and Intractability: A Guide to the Theory of NP-Completeness.New York: W.H. Freeman, 1979.
[18] M. Gyssens,J. Paredaens,, and D. Van Gucht,“A graph-oriented object database model,” Proc. Ninth ACM Symp. Principles of Database Systems, pp. 417-424, Apr. 1990.
[19] F.G. Halasz, "Reflections on Notecards: Seven Issues for the Next Generation of Hypermedia Systems," Comm. ACM, Vol. 31, No. 7, July 1988, pp. 836-852.
[20] D. Harel, "On Visual Formalisms," Comm. ACM, May 1988, pp. 514-530.
[21] R. Hull and M. Yoshikawa,“ILOG: Declarative creation and manipulation of object identifiers,” Proc. 16th Int’l Conf. Very Large Data Bases, 1990.
[22] R. Hull and J. Su,“On the expressive power of database queries with intermediate types,” J. Computer and System Sciences, vol. 43, pp. 219-267, 1991.
[23] K. Jensen and N. Wirth,Pascal User Manual and Report.Heidelberg, Germany: Springer-Verlag, 1985.
[24] W. Kim, Introduction to Object-Oriented Databases, MIT Press, Cambridge, Mass., 1990.
[25] G.M. Kuper and M.Y. Vardi,“A new approach to database logic,” Proc. ACM Symp. Principles of Database Systems,Waterloo, Ont., Canada, pp. 86-96, 1984.
[26] M. Levene,The Nested Universal Relation Database Model. Lecture Notes in Computer Science, vol. 595. Heidelberg, Germany: Springer-Verlag, 1992.
[27] M. Levene and A. Poulovassilis, “The Hypernode Model and Its Associated Query Language,” Proc. Fifth Jerusalem Conf. Information Technology (JCIT-5), pp. 520-530, 1990.
[28] M. Levene and A. Poulovassilis, “An Object-Oriented Data Model Formalised through Hypergraphs,” Data and Knowledge Eng., vol. 6, no. 3, pp. 205-224, 1991.
[29] J. Leuchner,L. Miller,, and G. Slutzki,“Agreement graph dependencies.,” Bull. EATCS, vol. 45, pp. 202-217, 1991.
[30] Y.E. Lien,“On the equivalence of database models,” J. ACM, vol. 2, pp. 333-362, 1982.
[31] D. Maier,J.D. Ullman,, and M.Y. Vardi,“On the foundations of the universal relation model,” ACM Trans. Database Systems, vol. 9, pp. 283-308, 1984.
[32] S. Naqvi and S. Tsur, A Logical Language for Data and Knowledge Bases.New York: Computer Science Press, 1989.
[33] J. Nielsen, Hypertext and Hypermedia.New York: Academic Press, 1990.
[34] J. Paredaens, P. De Bra, M. Gyssens, and D. Van Gucht, The Structure of the Relational Database Model, vol. 17. Berlin: Springer-Verlag, 1989.
[35] J. Paredaens,P. Peelman,, and L. Tanca,“G-Log: A declarative graphical query language,” Proc. Int’l Conf. Deductive and Object-Oriented Databases,Munich, Germany, pp. 108-128, 1991.
[36] A. Poulovassilis and M. Levene, “A Nested-Graph Model for the Representation and Manipulation of Complex Objects,” ACM Trans. Information Systems, vol. 12, no. 1, pp. 35-68, 1994.
[37] R. Reiter,“On closed world databases,” Logic and Databases, H. Gallaire and J. Minker, eds. New York: Plenum Press, pp. 55-76, 1978.
[38] J. Richardson and P. Schwartz, "Aspects: Extending Objects to Support Multiple, Independent Roles," Proc. ACM SIGMOD Int'l Conf. Management of Data, pp. 298-307, 1991.
[39] F.W. Tompa, “A Data Model for Flexible Hypertext Database Systems,” ACM Trans. Information Systems, vol. 7, no. 1, pp. 85-100, 1989.
[40] S.J. Thomas and P.C. Fischer,“Nested relational structures,” Advances in Computing Research, P.C. Kanellakis and F. Preparata, eds., vol. 3. Greenwich, Conn.: JAI Press, pp. 269-307, 1986.
[41] S. Tsur,“Deductive databases in action,” Proc. ACM Symp. Principles of Database Systems,Denver, Colo., pp. 142-153, 1991.
[42] E. Tuv,A. Poulovassilis,, and M. Levene,“A storage manager for the hypernode model,” Proc. British Nat’l Conf. Databases,Aberdeen, Scotland, pp. 59-77, 1992.
[43] J. Ullman, Principles of Database and Knowledge-Base Systems, vol. 1. Computer Science Press, 1988.
[44] J.D. Ullman,“A comparison between deductive and object-oriented database systems,” Proc. Int’l Conf. Deductive and Object-Oriented Databases,Munich, Germany, pp. 263-277, 1991.
[45] M.Y. Vardi,“Fundamentals of dependency theory,” Trends in Theoretical Computer Science, chapt. 5, E. Borger, ed. Rockville, Md.: Computer Science Press, pp. 171-224, 1988.
[46] G.E. Weddell, Reasoning about Functional Dependencies Generalized for Semantic Data Models ACM Trans. Database Systems, vol. 17, no. 1, pp. 32-64, Mar. 1992.

Index Terms:
Graph-based data model, set-based data model, hypernode database, hypernode functional dependency, hypertext, query and update language, computable update, non-well-founded sets.
Mark Levene, George Loizou, "A Graph-Based Data Model and its Ramifications," IEEE Transactions on Knowledge and Data Engineering, vol. 7, no. 5, pp. 809-823, Oct. 1995, doi:10.1109/69.469818
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