Technical details
The W3 system has three parts which are independent of each other.
- Addressing
- Every document has a Universal Document Identifier (UDI) such as
http://info.cern.ch/hypertext/WWW/TheProject.html. The first part is
the access scheme (http, ftp, news, file, ...), then the host name,
then the path of the document on that host. A fragment after "#" names
a place within the document.
- Protocol
- HTTP, the HyperText Transfer Protocol, is as simple as possible. The
client connects to port 80, sends one line
GET /hypertext/WWW/TheProject.html
and the server replies with the document and closes the connection.
There are no headers, no status codes, no error messages: an error is
just a document which says so.
- Format
- HTML, the HyperText Markup Language, is an application of SGML. A
document uses a few tags: TITLE, H1 to H6 for headings, P for a
paragraph break, A with HREF for a link and NAME for an anchor, DL, DT
and DD for glossary lists, UL and LI for lists, PRE for preformatted
text. Browsers ignore tags they do not know, so documents stay readable
as the language grows.
Other data (plain text, files on FTP servers, news articles) is
accessed with the same browser; the browser negotiates the format with
the server.
See also the server ,
bibliography ,
the W3 project .