[egate.git] / doc / web.sgml

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  $Id: web.sgml,v 1.3 1996/08/09 15:42:13 adam Exp $
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<article>
<title>Web/Z39.50 gateway guide
<author>Europagate, 1996 <htmlurl url="http://europagate.dtv.dk"
 name="http://europagate.dtv.dk">
<date>$Revision: 1.3 $
<abstract>
This document describes a Web server that provides access to the
Z39.50 protocol.
</abstract>

<toc>

<sect>Introduction

<p>
The <htmlurl url="http://europagate.dtv.dk" name="EUROPAGATE">
project developed two Z39.50 gatways that served as
Z39.50 clients: an email gateway and a web gateway. This document
describes how to compile and install the web gateway. For information
about the email gateway see the document egate.txt.

<sect>Installation

<p>
An ANSI C compiler is required in order to compile the software.

The gateway uses IrTcl and YAZ from Index Data to interface the
Z39.50 protocol.

YAZ and IrTcl can be found at the FTP host:

<htmlurl url="ftp://ftp.indexdata.dk/index/yaz"
 name="ftp://ftp.indexdata.dk/index/yaz">

You also need the Tcl package which can be found at:

<htmlurl url="ftp://ftp.sunlabs.com/pub/tcl"
 name="ftp://ftp.sunlabs.com/pub/tcl">

Unpack <tt>egate.tar.gz</tt> and edit the top level
<tt/Makefile/. Specify where the YAZ package can be found by setting
the the include path <tt/ZINC/, and the YAZ library <tt/ZLIB/.
Some systems need extra socket libraries - in this case set the
<tt/ELIB/ variable. You need also to define the location of Tcl:
<tt/TCLLIB/ and <tt/TCLINC/ - and the location of IrTcl:
<tt/IRTCLLIB/ and <tt/IRTCLINC/.

The gateway scripts and the Z39.50 communication tools are located
in the <tt/EGWDIR/ directory. This setting is hardcoded in the
CGI program (<tt/egwcgi/) and therefore it must be defined before
compiling. The CGI program, <tt/egwcgi/, will be installed in the
<tt/CGIDIR/ directory. HTML - and images files are installed in
the <tt/HTDOCS/ and the <tt/GIFDIR/ directories respectively.

The shell variables <tt/CC/ and <tt/CFLAGS/ are used by the
<tt/Makefile/ so you may modify these in your shell before compiling.

Now, type <tt/make web/

If the compilation succeeds, you should install the software in target
directories, by issuing: <tt/make install.web/.

A HTML file called <tt/egwindex.html/ should be installed in your
<tt/HTDOCS/ directory. The page contains miscellaneous starting links
to the Z39.50 gateway. Read it with your browser and click on the
<it>single target</it> button to test it out.

<sect>Overview of the system
<p>

<sect1>The <tt/egwcgi/ program.
<p>
The <tt/egwcgi/ program uses the CGI interface to communicate with
your HTTP server. It is the only program that communicates with your
server and it needs to be installed in your CGI binaries directory
(<tt/CGIDIR/).

The program inspects the URL and contacts a shell server
specified after the name of the CGI program.
The URL takes the form:

http://host/cgi-bin/egwcgi/shell/argument

where <it/shell/ is the name of the shell server to invoke. The
<it/argument/ is transferred to the <it/shell/ program.

When the <tt/egwcgi/ program is started by a URL as above, it will
assign a unique session-ID. If the shell wishes to be stateful it
should return a page that includes references with the newly
assigned session-ID.
In this case all subsequent URLs should contain this session-ID
with the following form:

http://host/cgi-bin/egwcgi/sessionID/argument

The only difference from the initial URL is that the shell part is 
substituted with a numeric session-ID. If the <tt/egwcgi/ program
gets a reference to this kind of URL, it will try to contact a running
shell. If that fails, it will restart it. To communicate with the
shell the <tt/egwcgi/ program uses FIFOs (names pipes) whose names
include the session-ID.

The <tt/egwcgi/ program will initially change its current directory
to <tt/EGWDIR/ as specified in the <tt/Makefile/.

<sect1>The shell system.

<p>
The shell system is, basically, a shell program, a few maintenance
files, and a set of scripts. All files in the shell system are stored
in the <tt/EGWDIR/ directory.

The files are summarized below:

<descrip>
<tag/egwtcl/ A Tcl shell server - reads HTML with embedded Tcl and
commands to inspect CGI variables. Note: this shell is currently
unused because this shell doesn't support Z39.50.

<tag/egwirtcl/ The IrTcl shell server. The IrTcl shell reads HTML
files with embedded Tcl scripts as well as Z39.50 extensions added by the
IrTcl library. 

<tag/*.tcl/ Tcl scripts - located in the <tt/EGWDIR/ directory.
The <tt/z39util.tcl/ file declares a lot of Tcl functions to
facilitate Z39.50 communication as well as other utilities.

<tag/*.egw/ HTML files with embedded Tcl - located in the <tt/EGWDIR/
directory. Normally, each file correspond to one type of Web
page. For example, the <tt/query.egw/ file contacts a single
target and displays a search form; the <tt/search.egw/ file
makes a Z39.50 search/present and displays the result.

<tag/ztargets.conf/ Target configuration file. A sort of profile is
defined for each target: the name of the target, record syntax,
search fields and mapping to bib-1, etc.

<tag/egw.res/ Small configuration file; defines a shell's idle time,
the log-level, and the directory for FIFOs used by the gateway.
</descrip>

When the system is running a number of files are created:
<descrip>
<tag/www.db/ Database that maps from session-IDs to shells.

<tag/tcl.state.*/ User session states; these are stored as Tcl
variables.

<tag/egwcgi_log/ Log file for the <tt/egwcgi/ program.

<tag/egwsh_log/ Log file for the shells <tt/egwtcl/, <tt/egwirtcl/, etc.

<tag/irtcl_log/ YAZ log file created by the IrTcl library. The file
only includes information about Z39.50 communication.
</descrip>

<sect1>Tcl Scripts

<p>

The scripts with the extension <tt/egw/ are HTML files with embedded Tcl. 
Tcl code is initiated with a left curly brace <tt/{/ and is terminated
with a right curly brace <tt/}/. The Tcl code is executed on the
top level, i.e. variables are accessed in the global scope.
Standard Tcl commands, IrTcl commands (for Z39.50 communication), and
an extra set of "gateway" commands are available in the embedded Tcl code.
The extra set of commands are used to communicate with the Europagate
software:

<descrip>
<tag/html/ Concatenates the arguments and transfers them to the HTTP server.
The data may be cached. They are not written until the <tt/egw_flush/ is
invoked.
<tag/egw_form/ Inspects CGI form variables.
<tag/egw_parms/ Inspects URL variables.
<tag/egw_flush/ Flushes all HTML output.
<tag/egw_log/ Logs messages.
<tag/egw_enc/ Encodes URL data.
<tag/egw_wait/ Waits for events. One of the following events
will terminate this command: data from a Z39.50 server,
data from the CGI module, or timeout.
</descrip>

Note, that except from the <tt/html/ command all commands have a 
<tt/egw_/ - prefix.
Apart from the new commands, the following global variables are set:
<descrip>
<tag/sessionId/ ID of the current user session (integer).
<tag/env/ Array of environment variables - standard Tcl really.
</descrip>

<sect>LICENSE

<p>
 Copyright &copy; 1995-1996, the EUROPAGATE consortium (see below).

 The EUROPAGATE consortium members are:

<itemize>
<item>University College Dublin
<item>Danmarks Teknologiske Videnscenter
<item>An Chomhairle Leabharlanna
<item>Consejo Superior de Investigaciones Cientificas
</itemize>

 Permission to use, copy, modify, distribute, and sell this software and
 its documentation, in whole or in part, for any purpose, is hereby granted,
 provided that:

 1. This copyright and permission notice appear in all copies of the
 software and its documentation. Notices of copyright or attribution
 which appear at the beginning of any file must remain unchanged.

 2. The names of EUROPAGATE or the project partners may not be used to
 endorse or promote products derived from this software without specific
 prior written permission.

 3. Users of this software (implementors and gateway operators) agree to
 inform the EUROPAGATE consortium of their use of the software. This
 information will be used to evaluate the EUROPAGATE project and the
 software, and to plan further developments. The consortium may use
 the information in later publications.
 
 4. Users of this software agree to make their best efforts, when
 documenting their use of the software, to acknowledge the EUROPAGATE
 consortium, and the role played by the software in their work.

 THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
 EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
 WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 IN NO EVENT SHALL THE EUROPAGATE CONSORTIUM OR ITS MEMBERS BE LIABLE
 FOR ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF
 ANY KIND, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA
 OR PROFITS, WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND
 ON ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 USE OR PERFORMANCE OF THIS SOFTWARE.

</article>