2004/06/29 by Jan Van den Bussche, Bussche, Jan Van den, Dirk Van Gucht +3
Computer Science · #Advanced Database Systems and Queries #Databases (cs.DB) #FOS: Computer and information sciences #Logic, Reasoning, and Knowledge #Logic, programming, and type systems #Programming Languages (cs.PL) #cs.DB #cs.PL
paper · pdf · doi:10.48550/arxiv.cs/0406060
arxiv created 2004/06/29 · openalex publication_date 2004/06/29 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Two natural decision problems regarding the XML query language XQuery are well-definedness and semantic type-checking. We study these problems in the setting of a relational fragment of XQuery. We show that well-definedness and semantic type-checking are undecidable, even in the positive-existential case. Nevertheless, for a ``pure'' variant of XQuery, in which no identification is made between an item and the singleton containing that item, the problems become decidable. We also consider the analogous problems in the setting of the nested relational calculus.