This informational document is posted to news.answers, comp.infosystems.www, comp.infosystems.gopher, comp.infosystems.wais and alt.hypertext on the 1st and 15th of every month (please allow a day or two for it to propagate to your site). The latest version is always available on the web as <http://siva.cshl.org/~boutell/www_faq.html>. (see the section titled "What is a URL?" to understand what this means.)
The most recently posted version of this document is kept on the news.answers
archive on rtfm.mit.edu in /pub/usenet/news.answers/www/faq
Thomas Boutell
maintains this document. Feedback about it is to be
sent via e-mail to boutell@netcom.com.
In all cases, regard this document as out of date. Definitive
information should be on the web, and static versions such as this
should be considered unreliable at best. Please excuse any formatting
inconsistencies in the posted version of this document, as it is
automatically generated from the on-line version.
To access the web, you run a browser
program. The browser reads documents, and can fetch documents
from other sources. Information providers set up hypermedia
servers which browsers can get documents from.
The browsers can, in addition, access files by FTP, NNTP (the Internet news protocol), gopher
and an
ever-increasing range of other methods. On top of these, if the
server has search capabilities, the browsers will permit searches
of documents and databases.
The documents that the browsers display are hypertext documents.
Hypertext is text with pointers to other text. The browsers let you
deal with the pointers in a transparent way -- select the pointer, and
you are presented with the text that is pointed to.
Hypermedia is a superset of hypertext -- it is any medium with
pointers to other media. This means that browsers might not display a
text file, but might display images or sound or animations.
URLs look like this:
The first part of the URL, before the colon, specifies the access
method. The part of the URL after the colon is interpreted specific
to the access method. In general, two slashes after the colon
indicate a machine name (machine:port is also valid).
In this document, you will often see URLs surrounded by angle
brackets. This is done because some newsreaders (I am told)
can recognize them and treat them as "buttons". Do not enter
the angle brackets when entering a URL by hand to your
web browser.
If you only want to provide information to local users, placing your
information in local files is also an option. This means,
however, that there can be no off-machine access.
See http://info.cern.ch/hypertext/WWW/Daemon/Overview.html for more
information on writing servers and gateways in general.
Of course, most folks would still prefer to use a friendlier,
graphical editor.
One option is to use an SGML editor with the HTML
DTD
In addition, there are two collections of filters for converting
your existing documents (in TeX and other non-HTML formats)
into HTML automatically:
Rich Brandwein and Mike Sendall's List at CERN
NCSA's List of Filters and Editors
Finally, TkWWW (listed above under XWindows browsers) supports
HTML editing.
In practice, this means that WWW can represent the gopher (a menu is a
list of links, a gopher document is a hypertext document without
links, searches are the same, telnet sessions are the same) and WAIS
(a WAIS index is a searchable page, returning a document with no
links) data models as well as providing extra functionality.
The principal difference between the three systems, it turns out, is
deployment. WWW does not have as large a user base as gopher, mainly
because of the small number of WWW browsers that are out. This is
changing as WWW reaches critical mass (usage of the server at CERN
doubles every 4 months -- twice the rate of Internet expansion).
One of the few limitations of the current networked information
systems is that there is no simple way to find out what has changed,
what is new, or even what is out there. As a result, a definitive
list of the web's contents is impossible at this moment. There
are, however, several resources which provide a great deal of
information on new and established servers by topic. These
are just two:
To find out more, use the web. This FAQ hopefully provides
enough information for you to locate and install a browser
on your system. If you have system specific questions regarding
FTP, networking and the like, please consult newsgroups
relevant to your particular hardware and operating
system!
Later you may return to this FAQ for answers to some of the
advanced questions covered in the second section. The advanced
section contains the most-asked technical questions in the group.
There are really two issues here: how to indicate in HTML that
you want an image to be clickable, and how to configure your
server to do something with the clicks returned by Mosaic,
Chimera, and other clients capable of delivering them.
You can read about
image maps and the NCSA server at the URL
<http://hoohoo.ncsa.uiuc.edu/docs/setup/admin/Imagemap.html>.
Such links are useful when a form is intended to perform
some action on the server machine without sending new information to
the client, or when a user has clicked in an undefined area in
an image map; these are just two possibilities.
Rob McCool
of NCSA provided the following wisdom on the subject:
(You can learn more about nph scripts from the
NCSA server documentation
at the URL <http://hoohoo.ncsa.uiuc.edu/docs>.) Essentially they
are scripts that handle their own HTTP response codes.
Here are two ways:
1. Turn on "load to local disk" in your browser, if it has such an
option; then reload images. You'll be prompted for filenames
instead of seeing them on the screen. Be sure to shut it off
when you're done with it.
2. Choose "view source" and browse through the HTML source; find
the URL for the inline image of interest to you; copy and paste it
into the "Open URL" window. This should load it into your
image viewer instead, where you can save it and otherwise
muck about with it.
3: Elementary questions
3.1: What are WWW, hypertext and hypermedia?
WWW stands for "World Wide Web". The WWW project, started by CERN (the European Laboratory for
Particle Physics), seeks to build a distributed hypermedia system.3.2: What is a URL?
URL stands for "Uniform Resource Locator". It is a draft standard for
specifying
an object on the Internet, such as a file or newsgroup.
3.3: How can I access the web?
You have two options -- either use a browser that can be telnetted to,
or use a browser on your machine. 3.3.1: Browsers accessible by telnet
An up-to-date list of these is available on the Web as http://info.cern.ch/hypertext/WWW/FAQ/Bootstrap.html
and should be regarded as an authoritative list.
3.3.2: Obtaining browsers
The preferred method of access of the Web is to run a browser
yourself. Browsers are available for many platforms, both in source
and executable forms. Here is a list generated from the authoritative
list, http://info.cern.ch/hypertext/WWW/Clients.html.
Terminal based browsers
Macintosh
XWindows
NeXTStep
Batch Mode
Unreleased or Unsupported
Assumes a character-grid terminal
with cursor addressing, and provides
a full-screen interface to the web.
3.4: How can I provide information to the web?
Information providers run programs that the browsers can obtain
hypertext from. These programs can either be WWW servers that
understand the HyperText Transfer Protocol HTTP (best if you are
creating your information database from scratch), "gateway" programs
that convert an existing information format to hypertext, or a
non-HTTP server that WWW browsers can access -- anonymous FTP or
gopher, for example.3.4.1: Obtaining Servers
CERN's server is available for anonymous FTP from info.cern.ch and
many other places. Use archie to search for
"www" or "WWW" to find copies close to you. NCSA has also released
a server, available for FTP from ftp.ncsa.uiuc.edu.3.4.2: Producing HTML documents
There are several ways to produce HTML. One is to simply write it
by hand; try the "source" button of of your browser to look at the
HTML for an interesting page. The odds are that it'll be
a great deal simpler than you would expect. If you're used to
marking up text in any way (even red-pencilling it), HTML
should be rather intuitive.
A beginner's guide to HTML is available at
the URL <http://www.ncsa.uiuc.edu/General/Internet/WWW/HTMLPrimer.html>.
3.5: How does WWW compare to gopher and WAIS?
While all three of these information presentation systems are
client-server based, they differ in terms of their model of data. In
gopher, data is either a menu, a document, an index or a telnet
connection. In WAIS, everything is an index and everything that is
returned from the index is a document. In WWW, everything is a
(possibly) hypertext document which may be searchable.3.6: What is on the web?
Currently accessible through the web:
3.7: I want to know more
4: Advanced Questions
4.1: How do I set up a clickable image map?
4.2: How do I make a "link" that doesn't load a new page?
Yechezkal-Shimon Gutfreund (sg04@gte.com) wrote:
: Ok, here is another bizzare request from me:
: I am currently running scripts which I "DO NOT" want to return
: any visible result. That is, not text/plain, not text/HTML, not
: image/gif. The entire results are the side effects of the
: script and nothing should be returned to the viewer.
: It would be nice to have an internally supported null viewer
: so that I could do this, more "cleanly" (ok, ok, I hear your groans).
HTTP now supports a response code of 204, which is no operation. Some
browsers such as Mosaic/X 2.* support it. To use it, make your script a nph
script and output an HTTP/1.0 204 header. Something like:
HTTP/1.0 204 No response
Server: Myscript/NCSA httpd 1.1
4.3: Where can I learn how to create fill-out forms?
You can read about the Common Gateway Interface
at the URL
<http://hoohoo.ncsa.uiuc.edu:80/cgi/>. In addition to documenting
the standard interface for which scripts can now be written for
both NCSA and CERN-derived servers, these pages also cover
HTML forms and how to handle the results on the server side.
4.4: How can I save an inline image to disk?
5: Credits