<chapter id="architecture">
- <!-- $Id: architecture.xml,v 1.19 2007-02-02 09:58:39 marc Exp $ -->
<title>Overview of &zebra; Architecture</title>
<section id="architecture-representation">
<title>Local Representation</title>
-
+
<para>
As mentioned earlier, &zebra; places few restrictions on the type of
data that you can index and manage. Generally, whatever the form of
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>
+ </para>
+ <para>
The virtual Debian package <literal>idzebra-2.0</literal>
installs all the necessary packages to start
working with &zebra; - including utility programs, development libraries,
- documentation and modules.
- </para>
-
+ documentation and modules.
+ </para>
+
<section id="componentcore">
<title>Core &zebra; Libraries Containing Common Functionality</title>
<para>
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
+ libraries are responsible for
<variablelist>
<varlistentry>
<term>Dynamic Loading</term>
<listitem>
<para>of external filter modules, in case the application is
not compiled statically. These filter modules define indexing,
- search and retrieval capabilities of the various input formats.
+ search and retrieval capabilities of the various input formats.
</para>
</listitem>
</varlistentry>
<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
- lists in correct order.
+ lists in correct order.
</para>
</listitem>
</varlistentry>
components call resorting/re-ranking algorithms on the hit
sets. These might also be pre-sorted not only using the
assigned document ID's, but also using assigned static rank
- information.
+ information.
</para>
</listitem>
</varlistentry>
<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>
</varlistentry>
</variablelist>
</para>
- <para>
- The Debian package <literal>libidzebra-2.0</literal>
- contains all run-time libraries for &zebra;, the
- documentation in PDF and HTML is found in
+ <para>
+ 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>idzebra-2.0-doc</literal>, and
<literal>idzebra-2.0-common</literal>
includes common essential &zebra; configuration files.
</para>
</section>
-
+
<section id="componentindexer">
<title>&zebra; Indexer</title>
<para>
The <command>zebraidx</command>
- indexing maintenance utility
+ indexing maintenance utility
loads external filter modules used for indexing data records of
different type, and creates, updates and drops databases and
indexes according to the rules defined in the filter modules.
- </para>
- <para>
+ </para>
+ <para>
The Debian package <literal>idzebra-2.0-utils</literal> contains
the <command>zebraidx</command> utility.
</para>
<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>
+ great Information Retrieval server application.
+ </para>
+ <para>
The Debian package <literal>idzebra-2.0-utils</literal> contains
the <command>zebrasrv</command> utility.
</para>
</section>
<section id="componentyazserver">
- <title>YAZ Server Frontend</title>
+ <title>&yaz; Server Frontend</title>
<para>
- The YAZ server frontend is
- a full fledged stateful Z39.50 server taking client
- connections, and forwarding search and scan requests to the
+ 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.
</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="&url.srw;">SRU SOAP</ulink>
- requests, and
- <ulink url="&url.sru;">SRU REST</ulink>
+ <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>
+ translate incoming
+ <ulink url="&url.cql;">&acro.cql;</ulink>
queries to
- <ulink url="&url.yaz.pqf;">PQF</ulink>
+ <ulink url="&url.yaz.pqf;">&acro.pqf;</ulink>
queries, if
- correctly configured.
+ correctly configured.
</para>
<para>
- <ulink url="&url.yaz;">YAZ</ulink>
- is an Open Source
+ <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.
- It is packaged in the Debian packages
+ &acro.ansi; &acro.z3950;/ISO23950 standard for information retrieval.
+ It is packaged in the Debian packages
<literal>yaz</literal> and <literal>libyaz</literal>.
</para>
</section>
-
+
<section id="componentmodules">
<title>Record Models and Filter Modules</title>
<para>
- The hard work of knowing <emphasis>what</emphasis> to index,
+ The hard work of knowing <emphasis>what</emphasis> to index,
<emphasis>how</emphasis> to do it, and <emphasis>which</emphasis>
part of the records to send in a search/retrieve response is
- implemented in
+ implemented in
various filter modules. It is their responsibility to define the
exact indexing and record display filtering rules.
</para>
<para>
The virtual Debian package
<literal>libidzebra-2.0-modules</literal> installs all base filter
- modules.
+ modules.
</para>
+ <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>
+ <para>
+ 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 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 &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>
+ 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>
+ 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 XML Record Model and Filter Module</title>
+ <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>
+
<para>
- The Alvis filter for XML files is an 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
+ The Alvis filter for &acro.xml; files is an &acro.xslt; based input
+ filter.
+ 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 Alvis filter
+ uses &acro.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
+ 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>
Finally, the Alvis filter allows for static ranking at index
time, and to to sort hit lists according to predefined
static ranks. This imposes no overhead at all, both
- search and indexing perform still
+ 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>
</section>
<section id="componentmodulesgrs">
- <title>GRS Record Model and Filter Modules</title>
+ <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 GRS filter modules described in
+ The &acro.grs1; filter modules described in
<xref linkend="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
+ 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.
- GRS filters of various kind have also been called ABS filters due
+ &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
+ 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
+ index binary and &acro.xml; versions of traditional library &acro.marc; records
based on the ISO2709 standard. The Debian package for both
- filters is
+ filters is
<literal>libidzebra-2.0-mod-grs-marc</literal>.
</para>
<para>
- GRS TCL scriptable filters for extensive user configuration come
- in two flavors: a regular expression filter
+ &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
+ 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 SGML filter is called
+ A general purpose &acro.sgml; filter is called
<emphasis>grs.sgml</emphasis>. This filter is not yet packaged,
- but planned to be in the
+ 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
+ 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 XML and turn them into ID&zebra;'s internal GRS node
- trees. Have also a look at the Alvis XML/XSLT filter described in
+ 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>
<itemizedlist>
<listitem>
-
+
<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>
&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 retrival faster than regular
- retrieval operations (for MARC, XML etc).
+ 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>
<row>
<entry><literal>zebra::meta::sysno</literal></entry>
<entry>Get &zebra; record system ID</entry>
- <entry>XML and SUTRS</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
</row>
<row>
<entry><literal>zebra::data</literal></entry>
<row>
<entry><literal>zebra::meta</literal></entry>
<entry>Get &zebra; record internal metadata</entry>
- <entry>XML and SUTRS</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>XML and SUTRS</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
</row>
<row>
<entry>
<entry>
Get indexed keys for field <replaceable>f</replaceable> for record
</entry>
- <entry>XML and SUTRS</entry>
+ <entry>&acro.xml; and &acro.sutrs;</entry>
</row>
<row>
<entry>
Get indexed keys for field <replaceable>f</replaceable>
and type <replaceable>t</replaceable> for record
</entry>
- <entry>XML and SUTRS</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>
</screen>
</para>
<para>
- The special
- <literal>zebra::data</literal> element set name is
- defined for any record syntax, but will always fetch
+ 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.
+ specific transformations will be applied to the raw record data.
</para>
<para>
- Also, &zebra; internal metadata about the record can be accessed:
+ 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>XML</literal> record syntax only internal
- record system number, whereas
+ </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 sytem
+ </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>
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.
+ 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
+ queries
<screen>
Z> f @attr 1=title my
Z> format sutrs
Z> s 1+1
</screen>
will display all indexed tokens from all indexed fields of the
- first record, and it will display in <literal>SUTRS</literal>
- record syntax, whereas
+ 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> s 1+1
Z> elements zebra::index::title:p
Z> s 1+1
- </screen>
- displays in <literal>XML</literal> record syntax only the content
+ </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>Bib-1</literal> use
+ 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.
</note>
</section>
- </chapter>
+ </chapter>
<!-- Keep this comment at the end of the file
Local variables:
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
- sgml-parent-document: "zebra.xml"
+ sgml-parent-document: "idzebra.xml"
sgml-local-catalogs: nil
sgml-namecase-general:t
End:
projects / idzebra-moved-to-github.git / blobdiff