This function checks if *Readingname*`$name` is a valid format which consists of
* upper and lowercase letters [a-zA-Z]
* digits [0-9]
* underscore `_`
* minus `-`
* dot `.`
* slash `/`
If the identifier starts with a dot `.`, it's considered to be an internal identifier and is treated differently in visualization, i.e. hidden.
For valid identifiers a true value is returned, false otherwise. This function can be used in if-constructs directly to test whether a *Readingname* is valid or not.