As it is the space of names of this function???. it returns unknown function

declare namespace xf = “W3C XQuery 1.0 and XPath 2.0 Functions and Operators”
count(xf:distinct-values(input()/Titulos/Titulo))

Hello Alberto,
The “distinct-values” function was introduced in Tamino Version 4.2.1, so if you are using an earlier version of Tamino you will get a “Function Unknown” response. When you use Version 4.2.1 or later, the distinct-values function lies in the default “xf:” namespace so you do not need to explictly declare the namespace before using it.
HTH