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- $Id: egate.sgml,v 1.4 1995/07/06 12:34:50 adam Exp $
+ $Id: egate.sgml,v 1.5 1995/07/10 10:28:22 adam Exp $
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<article>
<title>Email/Z39.50 gateway guide
<author>Europagate, 1995
-<date>$Revision: 1.4 $
+<date>$Revision: 1.5 $
<abstract>
This document describes a Email server that provides access to the
Z39.50 protocol.
<sect>Introduction
<p>
-This document describes how to compile, install and setup the
-Email server (ES) software. It does not address the internal design of
-the software.
+This document describes an email server subsystem developed
+within the EUROPAGATE project. The first part of this document
+serves as an administrators guide, while the second part is a
+follow-up on the Design deliverable (WP4.1) that outline the
+deviations from the design. Also, the second part contains
+an overview of the source code.
-<sect>Before you begin
+<sect>Compilation
<p>
An ANSI C compiler is required in order to compile the ES software.
<url url="ftp://ftp.cnidr.org/pub/NIDR.tools/zdist/zdist102b1-1.tar.Z" >
The Zdist package doesn't support result-set references. Also, it has a few
-bugs. Therefore we've included a patch <tt/<zdist.patch/ which fixes
+bugs. Therefore we've included a patch <tt/zdist.patch/ which fixes
some of these bugs.
Run patch in the directory above <tt/zdist102b1-1/:
<tscreen><verb>
The ES has been tested with regex-0.12. Some systems, such as Linux,
comes with the regex package preinstalled.
-<sect>Compilation
-
-<p>
Unpack <tt>egate.tar.gz</tt> and edit the top level <tt/Makefile/. Specify
where the GNU regex package is located and specify whether you use
YAZ or zdist. One some systems, you may have to set the <tt/NETLIB/ as
the options specified after the two dashes are transferred to the
kernel.
-<sect1>With the monitor
+<sect1>Running with the monitor
<p>
The monitor must be running at all times in this mode. You should
The eti sets current directory to the path specified by option <tt>-c</tt>.
-<sect1>Without the monitor
+<sect1>Running without the monitor
<p>
In this mode you should never start the monitor.
both left and right (3) truncation indicated by a <tt/?/ on both
left and right side of a term.
<tag/n/ This character indicates that the CCL parser should announce
- no truncation (100) if no truncation was indicated.
+ no truncation (100) if no truncation was specified.
</descrip>
<tag/p/ Position attribute. Valus is an integer.
<tag/s/ Structure attribute. Value is an integer; or the
</verb></tscreen>
where the use attribute is <em/date/ and the relation is <em/greater than/.
+<sect>Implementation
+
+<p>
+The implementation of the email server includes all the modules described
+in the design deliverable.
+
+The work was roughly carried out as follows:
+<enum>
+<item>The logging facilities and resource management utilities were
+ implemented — virtually all other modules depend on these
+ modules.
+<item>A minimal ES was implemented — including a high-level
+ API to the Z39.50 sub-system and a CCL parser with a few
+ commands, such as FIND and SHOW. This version displayed MARC
+ records in a raw format. This version served as base for the URP.
+<item>The first version of the MARC display formatting tool, FML,
+ was implemented and included in the ES.
+<item>The ETI program was implemented along with the IPC
+ (interprocess communication) utilities based on FIFOs. Facilities
+ to keep connections alive (to Z39.50 targets) was implemented.
+ To identify a user, a file-resident symbol table (small database) was
+ implemented which maps a email username to a unique integer (email userid).
+<item>The protocol persistency was implemented and more CCL commands
+ were added.
+<item>The MONITOR program was implemented.
+</enum>
+
+The following sections cover the most important modules in the ES and
+deviations from the design.
+
+<sect1>Z39.50 Interface layer
+
+<p>
+The design report specified that the Zdist toolkit from CNIDR would
+be used in the ES to provide access to the Z39.50 protocol. The package
+was choosen bacause it is easy to use and, more important, we felt
+that the API would be reasonably stable and supported.
+
+Nevertheless it turned out that CNIDR choose to change the API
+completely around January 1995 and announced a new version
+called zdist102b1-1.
+
+<em>Note: As of this date the newest version of Zdist is still
+zdist102b1-1. CNIDR seems to concentracte on their Isite package
+which also includes a Zdist package presumably similar to the
+standalone Zdist package</em>
+
+During the work with the Zdist package a few bugs were discovered.
+Fortunately, they could be solved within a few days. We also
+discovered that the package lacks result-set references.
+We posted the bug fixes to Kevin Gamiel who is responsible for
+the package but we didn't get responses. So, eventually, we weren't
+satisfied with the package after all.
+
+In February some of us began the development of a new Z39.50 package
+called YAZ — in retrospect somewhat motivated by the
+experiences with existing Z39.50/SR toolkits.
+
+To support result-set references we chose to incorporate a YAZ
+interface in the ES also. And we designed and implemented a
+simple high-level Z39.50 origin API that supported both Zdist and YAZ.
+
+The protocol persistency module was implemented on top of
+the high-level API and not on top of Zdist. The obvious
+advantage is that the persistency module is not tied to one
+particular Z39.50/SR package.
+
+Persistency information stored for each user is simply:
+<itemize>
+<item>hostname and port number.
+<item>authentication string
+<item>selected database(s)
+<item>next result set number
+<item>next result set position
+<item>result set information
+</itemize>
+
+Information about each result set includes:
+<itemize>
+<item>name
+<item>size (number of hits)
+<item>database(s)
+<item>query
+</itemize>
+
+<sect1>CCL
+
+<p>
+The CCL was implemented as described in the design. A CCL utility
+was made as a separate module which implements a tokenization
+package and a parser which translates from FIND to RPN. The
+data structure used to represent the RPN query is also used in
+Z39.50 search API on top of YAZ or Zdist.
+
+The CCL parser is quite configurable. Token names can be redefined to
+one or more names (aliases). Also, the specification of mapping
+between CCL field names (qualifiers) and Bib-1 attributes can be
+specified in either the C API or a file.
+
+Although the Z39.50 system in the ES uses the Bib-1 attribute set, the
+CCL parser itself is not tied to Bib-1.
+
+<sect1>FML
+
+<p>
+
+<sect1>IPC
+
+<p>
+
<sect>LICENSE
<p>
projects / egate.git / commitdiff