XQuery from the Experts: A Guide to the W3C XML Query Language

Validation Context

Validation makes sense only in a given context. Validating a name element inside a user element checks that it contains first and last elements; while validating a name element inside an article element checks that it contains a string.

In addition to keeping track of the types of variables, the static environment contains a validation context. Initially, this context is set to global. During static analysis, when an element constructor with a given name is entered, the context is extended by that element name within the constructor. For example, consider the query in Listing 4.10, which constructs a user element, omitting the first name if it is too long, or the rating if it is too low.

Listing 4.10. Validation Context Specified ...