About
The domain name space is a name space for a DNS name that shows:
- a tree structure (ie hierarchical)
- where the hierarchy levels are separated by the dot character .
Each node on the tree corresponds to a resource set (which may be empty).
For more information, you should go to the DNS name page
Syntax
Syntax as specified by the rfc: 1)
<domain> ::= <subdomain> | " "
<subdomain> ::= <label> | <subdomain> "." <label>
<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]
<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
<let-dig-hyp> ::= <let-dig> | "-"
<let-dig> ::= <letter> | <digit>
<letter> ::= any one of the 52 alphabetic characters A through Z in
upper case and a through z in lower case
<digit> ::= any one of the ten digits 0 through 9