G. Kuper, Aggregation in Constraint Databases, Proc. Workshop on Principles and Practice of Constraint Programming, 166--173, 1993. Home/Search Document Not in Database Summary Related Articles Check |
This paper is cited in the following contexts:
Adding Constraints to Logic-based Formalisms - Maher (1999) (Correct)
....form p( x) c and (recursive) queries can be represented by (recursive) rules with the same syntax as CLP. Some operations such as aggregation (which is not first order) do not extend readily to constraints, in the sense that the query language is not closed unless further restrictions are made [27]. Despite close similarities with the previous formalisms, there are several operations that have greater relevance in a database context and have not been addressed above. Examples are testing whether a derived fact is subsumed by already known facts and testing whether a query uniformly ....
G. Kuper, Aggregation in Constraint Databases, Proc. Workshop on Principles and Practice of Constraint Programming, 166--173, 1993.
Constraint Databases: A Survey - Revesz (1998) (6 citations) (Correct)
....queries are always generic or isomorphism preserving, that is, if two input databases are isomorphic, then their outputs are also isomorphic [31] Clearly, this property of genericity is lost when constraints are added. Necessary modifications of the concept of genericity are investigated in [95, 109, 111]. Negative results are also interesting. The strongest negative result is that relational calculus with polynomial constraints over the real numbers cannot express even simple recursive queries like connectivity, transitive closure and parity of a relation [18] This results extends earlier work ....
....on it. Aggregation operators [87] have an important use in practical database query languages such as SQL. It is a challenging problem to define meaningful and efficiently evaluable aggregation operators on generalized databases. Maximum, minimum and area were proposed as aggregation operators in [95]. More recent work on this problem appears in [40, 37, 67] Indefinite information represented by null values is also a practical concern. Null values represent either unknown or unexisting values. Evaluation of constraint queries with null values is considered in [90, 91, 134] Complex values are ....
G.M. Kuper. Aggregation in Constraint Databases. Proc. Workshop on the Principles and Practice of Constraint Programming, 176--183, 1993.
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