 <a>constraint components</a> are declared.
					The optional property <code>sh:returnType</code> can be used to specify the type of results
					produced by the function.
					Finally, <code>sh:JSFunction</code> is a subclass of <code>sh:JSExecutable</code>, and
					the syntax rules of <a>JavaScript executables</a> apply to functions, too.
					In particular, each JavaScript-based function has one <a>value</a> of <code>sh:jsFunctionName</code>.
					This is the name of the JavaScript function that is exec