Relative naming

The address of a hypertext document is normally given within the context of another hypertext document. Where the addresses of the two documents are the similar, this allows only the difference between the two names to be given, saving space. An example is the address of the destination of a hypertext link , which is specified relative to the source document address.

(A futher practical advantage is that a group of documents may be transmitted without internal changes, or accessed using more than one address.)

This implies that certain characters ("/", "..") have a significance reserved for representing a hierarchical space, and must be recognized as such by both clients and servers.

In the WWW address format , the rules for relative naming are:

• If the " scheme " parts are different, the whole absolute address must be given. Other wise, the scheme is omitted, and:
• If the "host" and/or "port" parts are different, the host name and all the rest of the address must be given. The host name may be given using internet hostname conventions, ie domains may be omitted where different. This is not very well defined: one tends to assume that if any dot is present, then the full domain name is being given, up to the root (.) domain, while if there are no dots, the domain is the same as that of the hostname part of the the base address.
• If the access and host parts are the same, then the path may be given with the unix convention, including the use of ".." to mean indicate deletion of a path element. Within the path:
• If a leading slash is present, the path is absolute. Otherwise:
• The last part of the path of the base address (e.g. the filename of the current document) is removed, and the given relative address appended in its place.
• Within the result, all occurences "xxx/.." or "/." are recursively removed, where xxx is one path element (directory).

The use of the slash "/" and double dot ".." in this case must be respected by all servers. If necessary, this may mean converting their local representations in order that these characters should not appear within path elements (see "escaping" ).