Synonyms
C-tables; Extended relations
Definition
A conditional table [4] generalizes relations in two ways. First, in the entries in the columns, variables, representing unknown values, are allowed in addition to the usual constants. The second generalization is that each tuple is associated with a condition, which is a Boolean combination of atoms of the form x = y, x = a, a = b, for x, y null values (variables), and a, b constants. A conditional table essentially represents an existentially quantified function free first order theory.
Formally, let con be a countably infinite set of constants, and var be a countably infinite set of variables, disjoint from con. Let U be a finite set of attributes, and R ⊆ U a relational schema. A tuple in a c-table over R is a mapping from R, and a special attribute, denoted φ, to con ∪ var ∪ β, where β is the set of all Boolean combinations of equality atoms, as above. Every attribute in R maps to a variable or a constant, and φ maps to β. In a...
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Abiteboul S., Duschka O.M. Complexity of Answering Queries Using Materialized Views. In Proc. 17th ACM SIGACT-SIGMOD-SIGART Symp. on Principles of Database Systems, 1998, pp. 254–263.
Abiteboul S., Kanellakis P.C., Grahne G. On the Representation and Querying of Sets of Possible Worlds. Theor. Comput. Sci., 78(1):158–187, 1991.
Grahne G., Mendelzon A.O. Tableau Techniques for Querying Information Sources through Global Schemas. In Proc. 7th Int. Conf. on Database Theory, 1999, pp. 332–347.
Imielinski T., Lipski W. Jr. Incomplete Information in Relational Databases. J. ACM, 31(4):761–791, 1984.
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Grahne, G. (2009). Conditional Tables. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_1253
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DOI: https://doi.org/10.1007/978-0-387-39940-9_1253
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