[_a_a_a_]

Thank you. I guess I misread.

"For example, e-mails and urls are a special syntax. Their value space..." seemed to talk about the 'value space' of strings (these being e-mails and urls), not types (of e-mails and urls), which confused me.

[acchow]

It is bout the 'value space' of strings. Think of all possible strings. That is the entire value space of strings. Not every possible string is an email. Only a subset of this value space is a valid email. This subset is the 'value space' of strings which are valid emails.