August 2003
Intermediate to advanced
512 pages
11h 23m
English
book
XQuery from the Experts: A Guide to the W3C XML Query Language
by Howard Katz - Editor, Don Chamberlin, Denise Draper, Mary Fernández, Michael Kay, Jonathan Robie, Michael Rys, Jérôme Siméon, Jim Tivy, Philip Wadler
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Operators
The queries we have shown up to now all contain operators, which we have not yet covered. Like most languages, XQuery has arithmetic operators and comparison operators, and because sequences of nodes are a fundamental datatype in XQuery, it is not surprising that XQuery also has node sequence operators. This section describes these operators in some detail. In particular, it describes how XQuery treats some of the cases that arise quite easily when processing XML; for instance, consider the following expression: 1 * $b. How is this interpreted if $b is an empty sequence, untyped character data, an element, or a sequence of five nodes? Given the flexible structure of XML, it is imperative that cases like this be well defined in the language. ...