[1]

S. Abiteboul and C. Beeri. *On the Power of Languages for the Manipulation of Complex Objects*. Technical Report 846, INRIA, May 1988.

[2]

S. Abiteboul and S. Grumbach, COL: a logic-based language for complex objects. In

*Proc. of the Workshop on Database Programming Languages*, pages 253–276, Roscoff, France, September 1987.

Google Scholar[3]

A.V. Aho and J.D. Ullman. Universality of data retrieval languages. In *Proc. Sixth ACM Symp. on Principles of Programming Languages*, pages 110–117, January 1979.

[4]

H. Ait-Kaci and R. Nasr. LOGIN: a logic programming language with built-in inheritance.

*Journal of Logic Programming*, 3:185–215, 1986.

CrossRefGoogle Scholar[5]

K. Apt, H. Blair, and A. Walker. Towards a theory of declarative knowledge. In J. Minker, editor, *Foundations of Deductive Databases and Logic Programming*, pages 89–184, Morgan Kaufman Publishers, 1987.

[6]

Krzysztof R. Apt and M.H. Van Emden. Contributions to the theory of logic programming.

*Journal of the ACM*, 29(3):841–862, July 1982.

CrossRefGoogle Scholar[7]

F. Bancilhon and S. Khoshafian. A calculus for complex objects. In *Proc. Fifth ACM Symp. on Principles of Database Systems*, pages 53–59, 1986.

[8]

F. Bancilhon, P. Richard, and M. Scholl. On line processing of compacted relations. In *Proc. Intl. Conf. on Very Large Data Bases*, pages 263–269, 1982.

[9]

C. Beeri, S. Naqvi, R. Ramakrishnan, O. Shmueli, and S. Tsur. Sets and negation in a logic database language (LDL1). In *Proc. Sixth ACM Symp. on Principles of Database Systems*, pages 21–37, March 1987.

[10]

A. Chandra and D. Harel. Structure and complexity of relational queries.

*Journal of Computer and System Sciences*, 25(1):99–128, 1982.

CrossRefGoogle Scholar[11]

A.K. Chandra and D. Harel. Computable queries for relational datbase systems.

*Journal of Computer and System Sciences*, 21(2):156–178, 1980.

CrossRefGoogle Scholar[12]

P. Dadam et. al. A DBMS prototype to support extended *NF*
^{2} relations: an integrated view on flat tables and hierarchies. In *ACM SIGMOD Intl. Conf. on Management of Data*, pages 356–367, 1986.

[13]

M. Fitting. Enumeration operators and modular logic programming.

*J. of Logic Programming*, 4:11–21, 1987.

CrossRefGoogle Scholar[14]

M. Gyssens and D. Van Gucht. The powerset algebra as a result of adding programming constructs to the nested relational algebra. In *ACM SIGMOD Intl. Conf. on Management of Data*, pages 225–232, 1988.

[15]

R. Hull and J. Su. On the expressive power of database queries with intermediate types. In *Proc. Seventh ACM Symp. on Principles of Database Systems*, pages 39–51, 1988.

[16]

R. Hull and J. Su. Untyped sets, invention, and computable queries. In *Proc. Eighth ACM Symp. on Principles of Database Systems*, 1989.

[17]

M. Kifer and J. Wu. A logic for object-oriented logic programming (Maier's O-Logic revisited). In *Proc. Eighth ACM Symp. on Principles of Database Systems*, 1989.

[18]

G.M. Kuper. Logic programming with sets. In *Proc. Sixth ACM Symp. on Principles of Database Systems*, pages 11–20, 1987.

[19]

G.M. Kuper. On the expressive power of logic programming with sets. In *Proc. Seventh ACM Symp. on Principles of Database Systems*, pages 10–14, 1988.

[20]

G.M. Kuper and M.Y. Vardi. On the complexity of queries in the logical data model. In D. Van Gucht M. Gyssens, J. Paredaens, editor,

*2nd International Conference on Database Theory*, pages 267–280, Springer-Verlag, Bruges, Belgium, August 1988.

Google Scholar[21]

V. Linnemann. Non first normal form relations and recursive queries: an SQL-based approach. In *Proc. Intl. Conf. on Data Engineering*, pages 591–598, 1987.

[22]

H.-B. Paul, H.-J. Schek, M.H. Scholl, G. Weikum, and U. Deppisch. Architecture and implementation of the Darmstadt database kernel system. In *ACM SIGMOD Intl. Conf. on Management of Data*, 1987.

[23]

Y. Sagiv and M. Yannakakis. Equivalence among relational expressions with the union and difference operators.

*Journal of the ACM*, 27(4):633–655, 1980.

CrossRefGoogle Scholar[24]

H.-J. Schek and M.H. Scholl. An algebra for the relational model with relation-valued attributes.

*Information Systems*, 11(2):137–147, 1986.

CrossRefGoogle Scholar[25]

A. Tarski. A lattice theoretical fixpoint theorem and its applications.

*Pacific J. Math.*, 5(2):285–309, 1955.

Google Scholar[26]

J.D. Ullman. *Principles of Database and Knowledge-Base Systems*. Computer Science Press, 1988.