-<!-- $Id: introduction.xml,v 1.3 2001-08-13 09:42:54 adam Exp $ -->
- <chapter><title>Introduction</title>
-
+ <chapter id="introduction"><title>Introduction</title>
+
+ <para>
+ &yaz; is a C/C++ library for information retrieval applications
+ using the Z39.50/SRU/Solr protocols for information retrieval.
+ </para>
+
<para>
- The &yaz; toolkit offers several different levels of access to the
- Z39.50 and SR protocols. The level that you need to use depends on
- your requirements, and the role (server or client) that you
- want to implement.
- </para><para>
- The basic level, which is independent of the role, consists of three
- primary interfaces:
-
+ Properties of &yaz;:
<itemizedlist>
- <listitem><para>&asn;, which provides a C representation of the Z39.50/SR
- protocol packages (PDUs).
+ <listitem><para>
+ Complete
+ <ulink url="&url.z39.50;">Z39.50</ulink> version 3 support.
+ Amendments and Z39.50-2002 revision is supported.
+ </para></listitem>
+ <listitem><para>
+ Supports
+ <ulink url="&url.sru;">SRU GET/POST/SOAP</ulink>
+ version 1.2 (over HTTP and HTTPS).
+ </para></listitem>
+ <listitem><para>
+ Includes BER encoders/decoders for the
+ <ulink url="&url.ill;">ISO ILL</ulink>
+ protocol.
+ </para></listitem>
+ <listitem><para>
+ Supports
+ <ulink url="&url.solr;">Solr</ulink> Web Service version 1.4.x (client side only)
</para></listitem>
- <listitem><para>&odr;, which encodes and decodes the packages according
- to the BER specification.
+ <listitem><para>
+ Supports the following transports: BER over TCP/IP
+ (<ulink url="&url.ber.over.tcpip;">RFC1729</ulink>),
+ BER over unix local socket, and
+ <ulink url="&url.http.1.1;">HTTP 1.1</ulink>.
</para></listitem>
- <listitem><para>&comstack;, which exchanges the encoded packages with
- a peer process over a network.
+ <listitem><para>
+ Secure Socket Layer support using
+ <ulink url="&url.gnutls;">GNU TLS</ulink> or
+ <ulink url="&url.openssl;">OpenSSL</ulink>.
+ If enabled, &yaz; uses HTTPS transport (for SOAP) or
+ "Secure BER" (for Z39.50).
+ </para></listitem>
+ <listitem><para>
+ Offers
+ <ulink url="&url.zoom;">ZOOM</ulink> C API implementing
+ Z39.50, SRU and Solr Web Service.
+ </para></listitem>
+ <listitem><para>
+ The &yaz; library offers a set of useful utilities
+ related to the protocols, such as MARC (ISO2709) parser,
+ CCL (ISO8777) parser,
+ <ulink url="&url.cql;">CQL</ulink>
+ parser, memory management routines, character set conversion.
+ </para></listitem>
+ <listitem><para>
+ Portable code. &yaz; compiles out-of-the box on most Unixes and
+ on Windows using Microsoft Visual C++.
+ </para></listitem>
+ <listitem><para>
+ Fast operation. The C based BER encoders/decoders as well
+ as the server component of &yaz; is very fast.
+ </para></listitem>
+ <listitem><para>
+ Liberal license that allows for commercial use of &yaz;.
</para></listitem>
</itemizedlist>
-
- The &asn; module represents the ASN.1 definition of
- the SR/Z39.50 protocol. It establishes a set of type and
- structure definitions, with one structure for each of the top-level
- PDUs, and one structure or type for each of the contained ASN.1 types.
- For primitive types, or other types that are defined by the ASN.1
- standard itself (such as the EXTERNAL type), the C representation is
- provided by the &odr; (Open Data Representation) subsystem.
- </para>
- <para>
- &odr; is a basic mechanism for representing an
- ASN.1 type in the C programming language, and for implementing BER
- encoders and decoders for values of that type. The types defined in
- the &asn; module generally have the prefix <literal>Z_</literal>, and
- a suffix corresponding to the name of the type in the ASN.1
- specification of the protocol (generally Z39.50-1995). In the case of
- base types (those originating in the ASN.1 standard itself), the prefix
- <literal>Odr_</literal> is sometimes seen. Either way, look for
- the actual definition in either <filename>proto.h</filename> (for the types
- from the protocol), <filename>odr.h</filename> (for the primitive ASN.1
- types, or <filename>odr_use.h</filename> (for the ASN.1
- <emphasis>useful</emphasis> types). The &asn; library also
- provides functions (which are, in turn, defined using &odr;
- primitives) for encoding and decoding data values. Their general form is
-
- <synopsis>
- int z_xxx(ODR o, Z_xxx **p, int optional, const char *name);
- </synopsis>
- (note the lower-case "z" in the function name)
</para>
- <note>
- <para>
- If you are using the premade definitions of the &asn; module, and you
- are not adding new protocol of your own, the only parts of &odr; that you
- need to worry about are documented in section
- <link linkend="odr-use">Using ODR</link>.
+ <sect1 id="introduction.reading"><title>Reading this Manual</title>
+ <para>Most implementors only need to read a fraction of the
+ material in thie manual, so a quick walkthrough of the chapters
+ is in order.
</para>
- </note>
+ <itemizedlist>
+ <listitem>
+ <para>
+ <xref linkend="installation"/> contains installation
+ instructions for &yaz;. You don't need reading this
+ if you expect to download &yaz; binaries.
+ However, the chapter contains information about how
+ to make <emphasis>your</emphasis> application link
+ with &yaz;.
+ </para>
+ </listitem>
- <para>
- When you have created a BER-encoded buffer, you can use the &comstack;
- subsystem to transmit (or receive) data over the network. The &comstack;
- module provides simple functions for establishing a connection
- (passively or actively, depending on the role of your application),
- and for exchanging BER-encoded PDUs over that connection. When you
- create a connection endpoint, you need to specify what transport to
- use (OSI or TCP/IP), and which protocol you want to use (SR or
- Z39.50). For the remainder of the connection's lifetime, you don't have
- to worry about the underlying transport protocol at all - the &comstack;
- will ensure that the correct mechanism is used.
+ <listitem>
+ <para>
+ <xref linkend="zoom"/> describes the ZOOM API of &yaz;.
+ This is definitely worth a read if you wish to develop a Z39.50/SRU
+ client.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="server"/> describes the generic frontend server
+ and explains how to develop server Z39.50/SRU applications for &yaz;.
+ Obviously worth reading if you're to develop a server.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="yaz-client"/> describes how to use the &yaz; Z39.50
+ client. If you're developer and wish to test your server
+ or a server from another party, you might find this chapter
+ useful.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="asn"/> documents the most commonly used Z39.50
+ C data structures offered by the &yaz; API. Client
+ developers using ZOOM and non-Z39.50 implementors may skip this.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="soap"/> describes how SRU and SOAP is used
+ in &yaz;. Only if you're developing SRU applications
+ this section is a must.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="tools"/> contains sections for the various
+ tools offered by &yaz;. Scan through the material quickly
+ and see what's relevant to you! SRU implementors
+ might find the <link linkend="cql">CQL</link> section
+ particularly useful.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="odr"/> goes through the details of the
+ ODR module which is the work horse that encodes and decodes
+ BER packages. Implementors using ZOOM only, do <emphasis>not</emphasis>
+ need reading this.
+ Most other Z39.50 implementors only need to read the first two
+ sections (<xref linkend="odr.introduction"/> and
+ <xref linkend="odr.use"/>).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <xref linkend="comstack"/> describes the network layer module
+ COMSTACK. Implementors using ZOOM or the generic frontend server
+ may skip this. Others, presumably, handling client/server
+ communication on their own should read this.
+ </para>
+ </listitem>
+
+ </itemizedlist>
+ </sect1>
+ <sect1 id="introduction.api"><title>The API</title>
+
+ <para>
+ The <ulink url="&url.yaz;">&yaz;</ulink>
+ toolkit offers several different levels of access to the
+ <ulink url="&url.z39.50;">ISO23950/Z39.50</ulink>,
+ <ulink url="&url.ill;">ILL</ulink> and
+ <ulink url="&url.sru;">SRU</ulink>
+ protocols.
+ The level that you need to use depends on your requirements, and
+ the role (server or client) that you want to implement.
+ If you're developing a client application you should consider the
+ <link linkend="zoom">ZOOM</link> API.
+ It is, by far, the easiest way to develop clients in C.
+ Server implementers should consider the
+ <link linkend="server">generic frontend server</link>.
+ None of those high-level APIs support the whole protocol, but
+ they do include most facilities used in existing Z39.50 applications.
+ </para>
+ <para>
+ If you're using 'exotic' functionality (meaning anything not included in
+ the high-level APIs), developing non-standard extensions to Z39.50 or
+ you're going to develop an ILL application you'll have to learn the lower
+ level APIs of &yaz;.
+ </para>
+ <para>
+ The YAZ toolkit modules is shown in figure <xref linkend="yaz.layer"/>.
+ </para>
+ <figure id="yaz.layer">
+ <title>YAZ layers</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="apilayer.png" format="PNG"/>
+ </imageobject>
+ <imageobject>
+ <imagedata fileref="apilayer.eps" format="EPS"/>
+ </imageobject>
+ </mediaobject>
+ </figure>
+ <para>
+ There are four layers.
+ <itemizedlist>
+ <listitem>
+ <para>A client or server application (or both).
+ This layer includes ZOOM and the generic frontend server.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The second layer provides a C represenation of the
+ protocol units (packages) for Z39.50 ASN.1, ILL ASN.1,
+ SRU.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The third layer encodes and decodes protocol data units to
+ simple packages (buffer with certain length). The &odr; module
+ encodes and decodes BER whereas the HTTP modules encodes and
+ decodes HTTP ruquests/responses.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The lowest layer is &comstack; which exchanges the encoded packages
+ with a peer process over a network.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The &asn; module represents the ASN.1 definition of
+ the Z39.50 protocol. It establishes a set of type and
+ structure definitions, with one structure for each of the top-level
+ PDUs, and one structure or type for each of the contained ASN.1 types.
+ For primitive types, or other types that are defined by the ASN.1
+ standard itself (such as the EXTERNAL type), the C representation is
+ provided by the &odr; (Open Data Representation) subsystem.
</para>
+ <para>
+ &odr; is a basic mechanism for representing an
+ ASN.1 type in the C programming language, and for implementing BER
+ encoders and decoders for values of that type. The types defined in
+ the &asn; module generally have the prefix <literal>Z_</literal>, and
+ a suffix corresponding to the name of the type in the ASN.1
+ specification of the protocol (generally Z39.50-1995). In the case of
+ base types (those originating in the ASN.1 standard itself), the prefix
+ <literal>Odr_</literal> is sometimes seen. Either way, look for
+ the actual definition in either <filename>z-core.h</filename> (for the types
+ from the protocol), <filename>odr.h</filename> (for the primitive ASN.1
+ types).
+ The &asn; library also provides functions (which are, in turn,
+ defined using &odr; primitives) for encoding and decoding data values.
+ Their general form is
+
+ <funcsynopsis>
+ <funcprototype><funcdef>int <function>z_<replaceable>xxx</replaceable></function></funcdef>
+ <paramdef>ODR <parameter>o</parameter></paramdef>
+ <paramdef>Z_<replaceable>xxx</replaceable> **<parameter>p</parameter></paramdef>
+ <paramdef>int <parameter>optional</parameter></paramdef>
+ <paramdef>const char *<parameter>name</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ (note the lower-case "z" in the function name)
+ </para>
+
+ <note>
+ <para>
+ If you are using the premade definitions of the &asn; module, and you
+ are not adding new protocol of your own, the only parts of &odr; that you
+ need to worry about are documented in
+ <xref linkend="odr.use"/>.
+ </para>
+ </note>
+
<para>
- We call the combined interfaces to &odr;, &asn;, and &comstack; the service
- level API. It's the API that most closely models the Z39.50/SR
+ When you have created a BER-encoded buffer, you can use the &comstack;
+ subsystem to transmit (or receive) data over the network. The &comstack;
+ module provides simple functions for establishing a connection
+ (passively or actively, depending on the role of your application),
+ and for exchanging BER-encoded PDUs over that connection. When you
+ create a connection endpoint, you need to specify what transport to
+ use (TCP/IP, SSL or UNIX sockets).
+ For the remainder of the connection's lifetime, you don't have
+ to worry about the underlying transport protocol at all - the &comstack;
+ will ensure that the correct mechanism is used.
+ </para>
+ <para>
+ We call the combined interfaces to &odr;, &asn;, and &comstack; the service
+ level API. It's the API that most closely models the Z39.50
service/protocol definition, and it provides unlimited access to all
- fields and facilities of the protocol definitions.
- </para>
- <para>
- The reason that the &yaz; service-level API is a conglomerate of the
- APIs from three different submodules is twofold. First, we wanted to allow
- the user a choice of different options for each major task. For instance,
- if you don't like the protocol API provided by &odr;/&asn;, you
- can use SNACC or BERUtils instead, and still have the benefits of the
- transparent transport approach of the &comstack; module. Secondly,
- we realize that you may have to fit the toolkit into an existing
- event-processing structure, in a way that
- is incompatible with the &comstack; interface or some other part of &yaz;.
- </para>
+ fields and facilities of the protocol definitions.
+ </para>
+ <para>
+ The reason that the &yaz; service-level API is a conglomerate of the
+ APIs from three different submodules is twofold. First, we wanted to allow
+ the user a choice of different options for each major task. For instance,
+ if you don't like the protocol API provided by &odr;/&asn;, you
+ can use SNACC or BERUtils instead, and still have the benefits of the
+ transparent transport approach of the &comstack; module. Secondly,
+ we realize that you may have to fit the toolkit into an existing
+ event-processing structure, in a way that is incompatible with
+ the &comstack; interface or some other part of &yaz;.
+ </para>
+ </sect1>
</chapter>
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