7.6
Functions
7.6.1
General considerations
This section defines the encoding of single valued functions using the fes:Function element. A function is a named procedure that performs a distinct computation. A function can accept zero or more arguments as input and generates a single result.
Functions may be used to extend the filter syntax with additional operators that can be used in filter expressions.
If a standard that references this International Standard extends the filter syntax using the fes:Function element, any additional functions shall be documented in the referencing standard. An implementation of the referencing standard shall, in its filter capabilities (see 7.14.6), declare these additional functions.
7.6.2
Encoding
The following XML Schema fragment declares the fes:Function element: