SilkRoute: trading between relations and XML
Proceedings of the 9th international World Wide Web conference on Computer networks : the international journal of computer and telecommunications netowrking
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Typechecking XML views of relational databases
ACM Transactions on Computational Logic (TOCL)
Typechecking for XML transformers
Journal of Computer and System Sciences - Special issue on PODS 2000
XML with data values: typechecking revisited
Journal of Computer and System Sciences - Special issu on PODS 2001
On the complexity of typechecking top-down XML transformations
Theoretical Computer Science - Database theory
Frontiers of tractability for typechecking simple XML transformations
Journal of Computer and System Sciences
A crash course on database queries
Proceedings of the twenty-sixth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
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The typechecking problem for transformations of relational data into tree data is the following: given a TreeQL program P (called transformation), and a DTD d (called output type), decide whether for every database instance D the result of the transformation P of D is of a type consistent with d (see [2]). TreeQL programs with projection-free conjunctive queries and DTDs with arbitrary regular expressions are considered here. A non-elementary upper bound for the typechecking problem is given in [2] (although in a more general setting, where equality and negation in projection-free conjunctive queries and additional universal integrity constraints are allowed). In this paper we show that the typechecking problem is in coNEXPTIME. As an intermediate step we consider the following problem, which can be formulated in a language independent of XML notions. Given a set of triples of the form (ϕ, k, j), where ϕ is a projection-free conjunctive query and k, j are natural numbers, decide whether there exists a database D such that for each triple (ϕ, k, j) in the set, there exists a natural number α, such that there are exactly k + j * α tuples satisfying the query ϕ in D. Our main technical contribution consists of a NEXPTIME algorithm for the last problem.