<chapter id="architecture">
- <!-- $Id: architecture.xml,v 1.10 2006-06-13 13:45:08 marc Exp $ -->
- <title>Overview of Zebra Architecture</title>
-
+ <title>Overview of &zebra; Architecture</title>
- <sect1 id="architecture-representation">
+ <section id="architecture-representation">
<title>Local Representation</title>
-
+
<para>
- As mentioned earlier, Zebra places few restrictions on the type of
+ As mentioned earlier, &zebra; places few restrictions on the type of
data that you can index and manage. Generally, whatever the form of
the data, it is parsed by an input filter specific to that format, and
- turned into an internal structure that Zebra knows how to handle. This
+ turned into an internal structure that &zebra; knows how to handle. This
process takes place whenever the record is accessed - for indexing and
retrieval.
</para>
<para>
The RecordType parameter in the <literal>zebra.cfg</literal> file, or
- the <literal>-t</literal> option to the indexer tells Zebra how to
+ the <literal>-t</literal> option to the indexer tells &zebra; how to
process input records.
Two basic types of processing are available - raw text and structured
data. Raw text is just that, and it is selected by providing the
- argument <emphasis>text</emphasis> to Zebra. Structured records are
+ argument <emphasis>text</emphasis> to &zebra;. Structured records are
all handled internally using the basic mechanisms described in the
subsequent sections.
- Zebra can read structured records in many different formats.
+ &zebra; can read structured records in many different formats.
<!--
How this is done is governed by additional parameters after the
"grs" keyword, separated by "." characters.
-->
</para>
- </sect1>
+ </section>
- <sect1 id="architecture-maincomponents">
+ <section id="architecture-maincomponents">
<title>Main Components</title>
<para>
- The Zebra system is designed to support a wide range of data management
+ The &zebra; system is designed to support a wide range of data management
applications. The system can be configured to handle virtually any
kind of structured data. Each record in the system is associated with
a <emphasis>record schema</emphasis> which lends context to the data
one database, the system poses no such restrictions.
</para>
<para>
- The Zebra indexer and information retrieval server consists of the
+ The &zebra; indexer and information retrieval server consists of the
following main applications: the <command>zebraidx</command>
indexing maintenance utility, and the <command>zebrasrv</command>
information query and retrieval server. Both are using some of the
same main components, which are presented here.
</para>
<para>
- The virtual Debian package <literal>idzebra1.4</literal>
+ The virtual Debian package <literal>idzebra-2.0</literal>
installs all the necessary packages to start
- working with Zebra - including utility programs, development libraries,
+ working with &zebra; - including utility programs, development libraries,
documentation and modules.
</para>
- <sect2 id="componentcore">
- <title>Core Zebra Libraries Containing Common Functionality</title>
+ <section id="componentcore">
+ <title>Core &zebra; Libraries Containing Common Functionality</title>
<para>
- The core Zebra module is the meat of the <command>zebraidx</command>
+ The core &zebra; module is the meat of the <command>zebraidx</command>
indexing maintenance utility, and the <command>zebrasrv</command>
information query and retrieval server binaries. Shortly, the core
libraries are responsible for
<varlistentry>
<term>Index Maintenance</term>
<listitem>
- <para> Zebra maintains Term Dictionaries and ISAM index
+ <para> &zebra; maintains Term Dictionaries and ISAM index
entries in inverted index structures kept on disk. These are
optimized for fast inset, update and delete, as well as good
search performance.
<varlistentry>
<term>Search Evaluation</term>
<listitem>
- <para>by execution of search requests expressed in PQF/RPN
+ <para>by execution of search requests expressed in &acro.pqf;/&acro.rpn;
data structures, which are handed over from
- the YAZ server frontend API. Search evaluation includes
+ the &yaz; server frontend &acro.api;. Search evaluation includes
construction of hit lists according to boolean combinations
of simpler searches. Fast performance is achieved by careful
use of index structures, and by evaluation specific index hit
<term>Record Presentation</term>
<listitem>
<para>returns - possibly ranked - result sets, hit
- numbers, and the like internal data to the YAZ server backend API
+ numbers, and the like internal data to the &yaz; server backend &acro.api;
for shipping to the client. Each individual filter module
implements it's own specific presentation formats.
</para>
</variablelist>
</para>
<para>
- The Debian package <literal>libidzebra1.4</literal>
- contains all run-time libraries for Zebra, the
+ The Debian package <literal>libidzebra-2.0</literal>
+ contains all run-time libraries for &zebra;, the
documentation in PDF and HTML is found in
- <literal>idzebra1.4-doc</literal>, and
- <literal>idzebra1.4-common</literal>
- includes common essential Zebra configuration files.
+ <literal>idzebra-2.0-doc</literal>, and
+ <literal>idzebra-2.0-common</literal>
+ includes common essential &zebra; configuration files.
</para>
- </sect2>
+ </section>
- <sect2 id="componentindexer">
- <title>Zebra Indexer</title>
+ <section id="componentindexer">
+ <title>&zebra; Indexer</title>
<para>
The <command>zebraidx</command>
indexing maintenance utility
indexes according to the rules defined in the filter modules.
</para>
<para>
- The Debian package <literal>idzebra1.4-utils</literal> contains
+ The Debian package <literal>idzebra-2.0-utils</literal> contains
the <command>zebraidx</command> utility.
</para>
- </sect2>
+ </section>
- <sect2 id="componentsearcher">
- <title>Zebra Searcher/Retriever</title>
+ <section id="componentsearcher">
+ <title>&zebra; Searcher/Retriever</title>
<para>
- This is the executable which runs the Z39.50/SRU/SRW server and
+ This is the executable which runs the &acro.z3950;/&acro.sru;/&acro.srw; server and
glues together the core libraries and the filter modules to one
great Information Retrieval server application.
</para>
<para>
- The Debian package <literal>idzebra1.4-utils</literal> contains
+ The Debian package <literal>idzebra-2.0-utils</literal> contains
the <command>zebrasrv</command> utility.
</para>
- </sect2>
+ </section>
- <sect2 id="componentyazserver">
- <title>YAZ Server Frontend</title>
+ <section id="componentyazserver">
+ <title>&yaz; Server Frontend</title>
<para>
- The YAZ server frontend is
- a full fledged stateful Z39.50 server taking client
+ The &yaz; server frontend is
+ a full fledged stateful &acro.z3950; server taking client
connections, and forwarding search and scan requests to the
- Zebra core indexer.
+ &zebra; core indexer.
</para>
<para>
- In addition to Z39.50 requests, the YAZ server frontend acts
+ In addition to &acro.z3950; requests, the &yaz; server frontend acts
as HTTP server, honoring
- <ulink url="http://www.loc.gov/standards/sru/srw/">SRW</ulink>
- SOAP requests, and
- <ulink url="&url.sru;">SRU</ulink>
- REST requests. Moreover, it can
+ <ulink url="&url.sru;">&acro.sru; &acro.soap;</ulink>
+ requests, and
+ &acro.sru; &acro.rest;
+ requests. Moreover, it can
translate incoming
- <ulink url="&url.cql;">CQL</ulink>
+ <ulink url="&url.cql;">&acro.cql;</ulink>
queries to
- <ulink url="http://indexdata.com/yaz/doc/tools.tkl#PQF">PQF</ulink>
+ <ulink url="&url.yaz.pqf;">&acro.pqf;</ulink>
queries, if
correctly configured.
</para>
<para>
- <ulink url="http://www.indexdata.com/yaz">YAZ</ulink>
+ <ulink url="&url.yaz;">&yaz;</ulink>
is an Open Source
toolkit that allows you to develop software using the
- ANSI Z39.50/ISO23950 standard for information retrieval.
+ &acro.ansi; &acro.z3950;/ISO23950 standard for information retrieval.
It is packaged in the Debian packages
<literal>yaz</literal> and <literal>libyaz</literal>.
</para>
- </sect2>
+ </section>
- <sect2 id="componentmodules">
+ <section id="componentmodules">
<title>Record Models and Filter Modules</title>
<para>
The hard work of knowing <emphasis>what</emphasis> to index,
</para>
<para>
The virtual Debian package
- <literal>libidzebra1.4-modules</literal> installs all base filter
+ <literal>libidzebra-2.0-modules</literal> installs all base filter
modules.
</para>
- <sect3 id="componentmodulestext">
- <title>TEXT Record Model and Filter Module</title>
- <para>
- Plain ASCII text filter. TODO: add information here.
- <!--
- <literal>text module missing as deb file<literal>
- -->
+ <section id="componentmodulesdom">
+ <title>&acro.dom; &acro.xml; Record Model and Filter Module</title>
+ <para>
+ The &acro.dom; &acro.xml; filter uses a standard &acro.dom; &acro.xml; structure as
+ internal data model, and can thus parse, index, and display
+ any &acro.xml; document.
</para>
- </sect3>
-
- <sect3 id="componentmodulesgrs">
- <title>GRS Record Model and Filter Modules</title>
<para>
- The GRS filter modules described in
- <xref linkend="record-model-grs"/>
- are all based on the Z39.50 specifications, and it is absolutely
- mandatory to have the reference pages on BIB-1 attribute sets on
- you hand when configuring GRS filters. The GRS filters come in
- different flavors, and a short introduction is needed here.
- GRS filters of various kind have also been called ABS filters due
- to the <filename>*.abs</filename> configuration file suffix.
+ A parser for binary &acro.marc; records based on the ISO2709 library
+ standard is provided, it transforms these to the internal
+ &acro.marcxml; &acro.dom; representation.
</para>
<para>
- The <emphasis>grs.danbib</emphasis> filter is developed for
- DBC DanBib records.
- DanBib is the Danish Union Catalogue hosted by DBC
- (Danish Bibliographic Center). This filter is found in the
- Debian package
- <literal>libidzebra1.4-mod-grs-danbib</literal>.
+ The internal &acro.dom; &acro.xml; representation can be fed into four
+ different pipelines, consisting of arbitrarily many successive
+ &acro.xslt; transformations; these are for
+ <itemizedlist>
+ <listitem><para>input parsing and initial
+ transformations,</para></listitem>
+ <listitem><para>indexing term extraction
+ transformations</para></listitem>
+ <listitem><para>transformations before internal document
+ storage, and </para></listitem>
+ <listitem><para>retrieve transformations from storage to output
+ format</para></listitem>
+ </itemizedlist>
</para>
<para>
- The <emphasis>grs.marc</emphasis> and
- <emphasis>grs.marcxml</emphasis> filters are suited to parse and
- index binary and XML versions of traditional library MARC records
- based on the ISO2709 standard. The Debian package for both
- filters is
- <literal>libidzebra1.4-mod-grs-marc</literal>.
- </para>
- <para>
- GRS TCL scriptable filters for extensive user configuration come
- in two flavors: a regular expression filter
- <emphasis>grs.regx</emphasis> using TCL regular expressions, and
- a general scriptable TCL filter called
- <emphasis>grs.tcl</emphasis>
- are both included in the
- <literal>libidzebra1.4-mod-grs-regx</literal> Debian package.
+ The &acro.dom; &acro.xml; filter pipelines use &acro.xslt; (and if supported on
+ your platform, even &acro.exslt;), it brings thus full &acro.xpath;
+ support to the indexing, storage and display rules of not only
+ &acro.xml; documents, but also binary &acro.marc; records.
</para>
<para>
- A general purpose SGML filter is called
- <emphasis>grs.sgml</emphasis>. This filter is not yet packaged,
- but planned to be in the
- <literal>libidzebra1.4-mod-grs-sgml</literal> Debian package.
+ Finally, the &acro.dom; &acro.xml; filter allows for static ranking at index
+ time, and to to sort hit lists according to predefined
+ static ranks.
</para>
<para>
- The Debian package
- <literal>libidzebra1.4-mod-grs-xml</literal> includes the
- <emphasis>grs.xml</emphasis> filter which uses <ulink
- url="http://expat.sourceforge.net/">Expat</ulink> to
- parse records in XML and turn them into IDZebra's internal GRS node
- trees. Have also a look at the Alvis XML/XSLT filter described in
- the next session.
- </para>
- </sect3>
+ Details on the experimental &acro.dom; &acro.xml; filter are found in
+ <xref linkend="record-model-domxml"/>.
+ </para>
+ <para>
+ The Debian package <literal>libidzebra-2.0-mod-dom</literal>
+ contains the &acro.dom; filter module.
+ </para>
+ </section>
+
+ <section id="componentmodulesalvis">
+ <title>ALVIS &acro.xml; Record Model and Filter Module</title>
+ <note>
+ <para>
+ The functionality of this record model has been improved and
+ replaced by the &acro.dom; &acro.xml; record model. See
+ <xref linkend="componentmodulesdom"/>.
+ </para>
+ </note>
- <sect3 id="componentmodulesalvis">
- <title>ALVIS Record Model and Filter Module</title>
<para>
- The Alvis filter for XML files is an XSLT based input
+ The Alvis filter for &acro.xml; files is an &acro.xslt; based input
filter.
- It indexes element and attribute content of any thinkable XML format
- using full XPATH support, a feature which the standard Zebra
- GRS SGML and XML filters lacked. The indexed documents are
- parsed into a standard XML DOM tree, which restricts record size
+ It indexes element and attribute content of any thinkable &acro.xml; format
+ using full &acro.xpath; support, a feature which the standard &zebra;
+ &acro.grs1; &acro.sgml; and &acro.xml; filters lacked. The indexed documents are
+ parsed into a standard &acro.xml; &acro.dom; tree, which restricts record size
according to availability of memory.
</para>
<para>
The Alvis filter
- uses XSLT display stylesheets, which let
- the Zebra DB administrator associate multiple, different views on
- the same XML document type. These views are chosen on-the-fly in
+ uses &acro.xslt; display stylesheets, which let
+ the &zebra; DB administrator associate multiple, different views on
+ the same &acro.xml; document type. These views are chosen on-the-fly in
search time.
</para>
<para>
In addition, the Alvis filter configuration is not bound to the
- arcane BIB-1 Z39.50 library catalogue indexing traditions and
+ arcane &acro.bib1; &acro.z3950; library catalogue indexing traditions and
folklore, and is therefore easier to understand.
</para>
<para>
static ranks. This imposes no overhead at all, both
search and indexing perform still
<emphasis>O(1)</emphasis> irrespectively of document
- collection size. This feature resembles Googles pre-ranking using
- their Pagerank algorithm.
+ collection size. This feature resembles Google's pre-ranking using
+ their PageRank algorithm.
</para>
<para>
- Details on the experimental Alvis XSLT filter are found in
+ Details on the experimental Alvis &acro.xslt; filter are found in
<xref linkend="record-model-alvisxslt"/>.
</para>
<para>
- The Debian package <literal>libidzebra1.4-mod-alvis</literal>
+ The Debian package <literal>libidzebra-2.0-mod-alvis</literal>
contains the Alvis filter module.
</para>
- </sect3>
+ </section>
+
+ <section id="componentmodulesgrs">
+ <title>&acro.grs1; Record Model and Filter Modules</title>
+ <note>
+ <para>
+ The functionality of this record model has been improved and
+ replaced by the &acro.dom; &acro.xml; record model. See
+ <xref linkend="componentmodulesdom"/>.
+ </para>
+ </note>
+ <para>
+ The &acro.grs1; filter modules described in
+ <xref linkend="grs"/>
+ are all based on the &acro.z3950; specifications, and it is absolutely
+ mandatory to have the reference pages on &acro.bib1; attribute sets on
+ you hand when configuring &acro.grs1; filters. The GRS filters come in
+ different flavors, and a short introduction is needed here.
+ &acro.grs1; filters of various kind have also been called ABS filters due
+ to the <filename>*.abs</filename> configuration file suffix.
+ </para>
+ <para>
+ The <emphasis>grs.marc</emphasis> and
+ <emphasis>grs.marcxml</emphasis> filters are suited to parse and
+ index binary and &acro.xml; versions of traditional library &acro.marc; records
+ based on the ISO2709 standard. The Debian package for both
+ filters is
+ <literal>libidzebra-2.0-mod-grs-marc</literal>.
+ </para>
+ <para>
+ &acro.grs1; TCL scriptable filters for extensive user configuration come
+ in two flavors: a regular expression filter
+ <emphasis>grs.regx</emphasis> using TCL regular expressions, and
+ a general scriptable TCL filter called
+ <emphasis>grs.tcl</emphasis>
+ are both included in the
+ <literal>libidzebra-2.0-mod-grs-regx</literal> Debian package.
+ </para>
+ <para>
+ A general purpose &acro.sgml; filter is called
+ <emphasis>grs.sgml</emphasis>. This filter is not yet packaged,
+ but planned to be in the
+ <literal>libidzebra-2.0-mod-grs-sgml</literal> Debian package.
+ </para>
+ <para>
+ The Debian package
+ <literal>libidzebra-2.0-mod-grs-xml</literal> includes the
+ <emphasis>grs.xml</emphasis> filter which uses <ulink
+ url="&url.expat;">Expat</ulink> to
+ parse records in &acro.xml; and turn them into ID&zebra;'s internal &acro.grs1; node
+ trees. Have also a look at the Alvis &acro.xml;/&acro.xslt; filter described in
+ the next session.
+ </para>
+ </section>
+
+ <section id="componentmodulestext">
+ <title>TEXT Record Model and Filter Module</title>
+ <para>
+ Plain ASCII text filter. TODO: add information here.
+ </para>
+ </section>
- <sect3 id="componentmodulessafari">
+ <!--
+ <section id="componentmodulessafari">
<title>SAFARI Record Model and Filter Module</title>
<para>
SAFARI filter module TODO: add information here.
- <!--
- <literal>safari module missing as deb file<literal>
- -->
</para>
- </sect3>
+ </section>
+ -->
- </sect2>
+ </section>
- </sect1>
+ </section>
- <sect1 id="architecture-workflow">
+ <section id="architecture-workflow">
<title>Indexing and Retrieval Workflow</title>
<para>
<para>
When records are accessed by the system, they are represented
- in their local, or native format. This might be SGML or HTML files,
- News or Mail archives, MARC records. If the system doesn't already
+ in their local, or native format. This might be &acro.sgml; or HTML files,
+ News or Mail archives, &acro.marc; records. If the system doesn't already
know how to read the type of data you need to store, you can set up an
input filter by preparing conversion rules based on regular
expressions and possibly augmented by a flexible scripting language
<para>
Before transmitting records to the client, they are first
converted from the internal structure to a form suitable for exchange
- over the network - according to the Z39.50 standard.
+ over the network - according to the &acro.z3950; standard.
</para>
</listitem>
</itemizedlist>
</para>
- </sect1>
-
+ </section>
+ <section id="special-retrieval">
+ <title>Retrieval of &zebra; internal record data</title>
+ <para>
+ Starting with <literal>&zebra;</literal> version 2.0.5 or newer, it is
+ possible to use a special element set which has the prefix
+ <literal>zebra::</literal>.
+ </para>
+ <para>
+ Using this element will, regardless of record type, return
+ &zebra;'s internal index structure/data for a record.
+ In particular, the regular record filters are not invoked when
+ these are in use.
+ This can in some cases make the retrieval faster than regular
+ retrieval operations (for &acro.marc;, &acro.xml; etc).
+ </para>
+ <table id="special-retrieval-types">
+ <title>Special Retrieval Elements</title>
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Element Set</entry>
+ <entry>Description</entry>
+ <entry>Syntax</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>zebra::meta::sysno</literal></entry>
+ <entry>Get &zebra; record system ID</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry><literal>zebra::data</literal></entry>
+ <entry>Get raw record</entry>
+ <entry>all</entry>
+ </row>
+ <row>
+ <entry><literal>zebra::meta</literal></entry>
+ <entry>Get &zebra; record internal metadata</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry><literal>zebra::index</literal></entry>
+ <entry>Get all indexed keys for record</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry>
+ <literal>zebra::index::</literal><replaceable>f</replaceable>
+ </entry>
+ <entry>
+ Get indexed keys for field <replaceable>f</replaceable> for record
+ </entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry>
+ <literal>zebra::index::</literal><replaceable>f</replaceable>:<replaceable>t</replaceable>
+ </entry>
+ <entry>
+ Get indexed keys for field <replaceable>f</replaceable>
+ and type <replaceable>t</replaceable> for record
+ </entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry>
+ <literal>zebra::snippet</literal>
+ </entry>
+ <entry>
+ Get snippet for record for one or more indexes (f1,f2,..).
+ This includes a phrase from the original
+ record at the point where a match occurs (for a query). By default
+ give terms before - and after are included in the snippet. The
+ matching terms are enclosed within element
+ <literal><s></literal>. The snippet facility requires
+ Zebra 2.0.16 or later.
+ </entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
+ </row>
+ <row>
+ <entry>
+ <literal>zebra::facet::</literal><replaceable>f1</replaceable>:<replaceable>t1</replaceable>,<replaceable>f2</replaceable>:<replaceable>t2</replaceable>,..
+ </entry>
+ <entry>
+ Get facet of a result set. The facet result is returned
+ as if it was a normal record, while in reality is a
+ recap of most "important" terms in a result set for the fields
+ given.
+ The facet facility first appeared in Zebra 2.0.20.
+ </entry>
+ <entry>&acro.xml;</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ <para>
+ For example, to fetch the raw binary record data stored in the
+ zebra internal storage, or on the filesystem, the following
+ commands can be issued:
+ <screen>
+ Z> f @attr 1=title my
+ Z> format xml
+ Z> elements zebra::data
+ Z> s 1+1
+ Z> format sutrs
+ Z> s 1+1
+ Z> format usmarc
+ Z> s 1+1
+ </screen>
+ </para>
+ <para>
+ The special
+ <literal>zebra::data</literal> element set name is
+ defined for any record syntax, but will always fetch
+ the raw record data in exactly the original form. No record syntax
+ specific transformations will be applied to the raw record data.
+ </para>
+ <para>
+ Also, &zebra; internal metadata about the record can be accessed:
+ <screen>
+ Z> f @attr 1=title my
+ Z> format xml
+ Z> elements zebra::meta::sysno
+ Z> s 1+1
+ </screen>
+ displays in <literal>&acro.xml;</literal> record syntax only internal
+ record system number, whereas
+ <screen>
+ Z> f @attr 1=title my
+ Z> format xml
+ Z> elements zebra::meta
+ Z> s 1+1
+ </screen>
+ displays all available metadata on the record. These include system
+ number, database name, indexed filename, filter used for indexing,
+ score and static ranking information and finally bytesize of record.
+ </para>
+ <para>
+ Sometimes, it is very hard to figure out what exactly has been
+ indexed how and in which indexes. Using the indexing stylesheet of
+ the Alvis filter, one can at least see which portion of the record
+ went into which index, but a similar aid does not exist for all
+ other indexing filters.
+ </para>
+ <para>
+ The special
+ <literal>zebra::index</literal> element set names are provided to
+ access information on per record indexed fields. For example, the
+ queries
+ <screen>
+ Z> f @attr 1=title my
+ Z> format sutrs
+ Z> elements zebra::index
+ Z> s 1+1
+ </screen>
+ will display all indexed tokens from all indexed fields of the
+ first record, and it will display in <literal>&acro.sutrs;</literal>
+ record syntax, whereas
+ <screen>
+ Z> f @attr 1=title my
+ Z> format xml
+ Z> elements zebra::index::title
+ Z> s 1+1
+ Z> elements zebra::index::title:p
+ Z> s 1+1
+ </screen>
+ displays in <literal>&acro.xml;</literal> record syntax only the content
+ of the zebra string index <literal>title</literal>, or
+ even only the type <literal>p</literal> phrase indexed part of it.
+ </para>
+ <note>
+ <para>
+ Trying to access numeric <literal>&acro.bib1;</literal> use
+ attributes or trying to access non-existent zebra intern string
+ access points will result in a Diagnostic 25: Specified element set
+ 'name not valid for specified database.
+ </para>
+ </note>
+ </section>
</chapter>
projects / idzebra-moved-to-github.git / blobdiff