XQuery for eXist - eXist: A NoSQL Database and Application Development Platform - page 112

The absence of the features does not mean that eXist is not type-
safe; it is, very much so. It only means that type checking based on
schema imports is not implemented.
eXist tested its implementation against the official XQuery Test Suite (XQTS version
1.0.2). Of the more than 14,000 tests, it passed over 99%.
eXist does not yet type-check the name of an element or attribute.
So, strangely enough, you can write let $elm as element(a) :=
<b/> and eXist will find it absolutely OK, although this is a relaxa‐
tion from the XQuery specification. The advice is not to use name
tests in element or attribute data type specifications, though. So,
use element() or attribute() instead of element(a) or
attribute(b) , since specifying a name implies type checking that
alas never occurs.
XQuery 3.0 Support
New since version 2.0 is eXist's support for XQuery 3.0 . As of writing, this specifica‐
tion had reached Proposed Recommendation status and several partial implementa‐
tions were available.
To enable the XQuery 3.0 support, start your XQuery program with:
xquery version "3.0" ;
XQuery 3.0 is a relatively new and probably not yet very well known standard. There‐
fore, the support eXist offers is handled in somewhat more detail next. For the exact
details, please refer to the standard .
XPath 3.0 functions
Many of the extra functions defined in XPath and XQuery 3.0 are implemented.
Among them are some very useful ones, like format-dateTime .
An exact list of what is available and what isn't can be found with the XQuery Func‐
tion Documentation browser in the dashboard. Browse the http://www.w3.org/
2005/xpath-functions module.
try/catch
The XQuery 3.0 try / catch mechanism allows you to catch errors raised during exe‐
cution. These can be errors raised by the XQuery engine (meaning your code did
something wrong), or errors you've explicitly raised with the error function. The