1 <chapter id="record-model-domxml">
2 <!-- $Id: recordmodel-domxml.xml,v 1.9 2007-02-22 15:44:19 marc Exp $ -->
3 <title>&dom; &xml; Record Model and Filter Module</title>
6 The record model described in this chapter applies to the fundamental,
8 record type <literal>&dom;</literal>, introduced in
9 <xref linkend="componentmodulesdom"/>. The &dom; &xml; record model
10 is experimental, and it's inner workings might change in future
11 releases of the &zebra; Information Server.
16 <section id="record-model-domxml-filter">
17 <title>&dom; Record Filter Architecture</title>
20 The &dom; &xml; filter uses a standard &dom; &xml; structure as
21 internal data model, and can therefore parse, index, and display
22 any &xml; document type. It is well suited to work on
23 standardized &xml;-based formats such as Dublin Core, MODS, METS,
24 MARCXML, OAI-PMH, RSS, and performs equally well on any other
25 non-standard &xml; format.
28 A parser for binary &marc; records based on the ISO2709 library
29 standard is provided, it transforms these to the internal
30 &marcxml; &dom; representation. Other binary document parsers
31 are planned to follow.
35 The &dom; filter architecture consists of four
36 different pipelines, each being a chain of arbitrarily many successive
37 &xslt; transformations of the internal &dom; &xml;
38 representations of documents.
41 <figure id="record-model-domxml-architecture-fig">
42 <title>&dom; &xml; filter architecture</title>
45 <imagedata fileref="domfilter.pdf" format="PDF" scale="50"/>
48 <imagedata fileref="domfilter.png" format="PNG"/>
51 <!-- Fall back if none of the images can be used -->
53 [Here there should be a diagram showing the &dom; &xml;
54 filter architecture, but is seems that your
55 tool chain has not been able to include the diagram in this
63 <table id="record-model-domxml-architecture-table" frame="top">
64 <title>&dom; &xml; filter pipelines overview</title>
70 <entry>Description</entry>
78 <entry><literal>input</literal></entry>
80 <entry>input parsing and initial
81 transformations to common &xml; format</entry>
82 <entry>Input raw &xml; record buffers, &xml; streams and
83 binary &marc; buffers</entry>
84 <entry>Common &xml; &dom;</entry>
87 <entry><literal>extract</literal></entry>
89 <entry>indexing term extraction
90 transformations</entry>
91 <entry>Common &xml; &dom;</entry>
92 <entry>Indexing &xml; &dom;</entry>
95 <entry><literal>store</literal></entry>
97 <entry> transformations before internal document
99 <entry>Common &xml; &dom;</entry>
100 <entry>Storage &xml; &dom;</entry>
103 <entry><literal>retrieve</literal></entry>
105 <entry>multiple document retrieve transformations from
106 storage to different output
107 formats are possible</entry>
108 <entry>Storage &xml; &dom;</entry>
109 <entry>Output &xml; syntax in requested formats</entry>
116 The &dom; &xml; filter pipelines use &xslt; (and if supported on
117 your platform, even &exslt;), it brings thus full &xpath;
118 support to the indexing, storage and display rules of not only
119 &xml; documents, but also binary &marc; records.
124 <section id="record-model-domxml-pipeline">
125 <title>&dom; &xml; filter pipeline configuration</title>
128 The experimental, loadable &dom; &xml;/&xslt; filter module
129 <literal>mod-dom.so</literal>
130 is invoked by the <filename>zebra.cfg</filename> configuration statement
132 recordtype.xml: dom.db/filter_dom_conf.xml
134 In this example the &dom; &xml; filter is configured to work
135 on all data files with suffix
136 <filename>*.xml</filename>, where the configuration file is found in the
137 path <filename>db/filter_dom_conf.xml</filename>.
140 <para>The &dom; &xslt; filter configuration file must be
141 valid &xml;. It might look like this:
144 <?xml version="1.0" encoding="UTF8"?>
145 <dom xmlns="http://indexdata.com/zebra-2.0">
147 <xmlreader level="1"/>
148 <!-- <marc inputcharset="marc-8"/> -->
151 <xslt stylesheet="common2index.xsl"/>
154 <xslt stylesheet="common2store.xsl"/>
157 <xslt stylesheet="store2dc.xsl"/>
159 <retrieve name="mods">
160 <xslt stylesheet="store2mods.xsl"/>
167 The root &xml; element <literal><dom></literal> and all other &dom;
168 &xml; filter elements are residing in the namespace
169 <literal>xmlns="http://indexdata.dk/zebra-2.0"</literal>.
172 All pipeline definition elements - i.e. the
173 <literal><input></literal>,
174 <literal><extract></literal>,
175 <literal><store></literal>, and
176 <literal><retrieve></literal> elements - are optional.
177 Missing pipeline definitions are just interpreted
178 do-nothing identity pipelines.
181 All pipeline definition elements may contain zero or more
182 <literal><![CDATA[<xslt stylesheet="path/file.xsl"/>]]></literal>
183 &xslt; transformation instructions, which are performed
184 sequentially from top to bottom.
185 The paths in the <literal>stylesheet</literal> attributes
186 are relative to zebras working directory, or absolute to the file
191 <section id="record-model-domxml-pipeline-input">
192 <title>Input pipeline</title>
194 The <literal><input></literal> pipeline definition element
195 may contain either one &xml; Reader definition
196 <literal><![CDATA[<xmlreader level="1"/>]]></literal>, used to split
197 an &xml; collection input stream into individual &xml; &dom;
198 documents at the prescribed element level,
201 <literal><![CDATA[<marc inputcharset="marc-8"/>]]></literal>, which defines
202 a conversion to &marcxml; format &dom; trees. The allowed values
203 of the <literal>inputcharset</literal> attribute depend on your
204 local <productname>iconv</productname> set-up.
207 Both input parsers deliver individual &dom; &xml; documents to the
208 following chain of zero or more
209 <literal><![CDATA[<xslt stylesheet="path/file.xsl"/>]]></literal>
210 &xslt; transformations. At the end of this pipeline, the documents
211 are in the common format, used to feed both the
212 <literal><extract></literal> and
213 <literal><store></literal> pipelines.
217 <section id="record-model-domxml-pipeline-extract">
218 <title>Extract pipeline</title>
220 The <literal><extract></literal> pipeline takes documents
221 from any common &dom; &xml; format to the &zebra; specific
222 indexing &dom; &xml; format.
223 It may consist of zero ore more
224 <literal><![CDATA[<xslt stylesheet="path/file.xsl"/>]]></literal>
225 &xslt; transformations, and the outcome is handled to the
226 &zebra; core to drive the process of building the inverted
228 <xref linkend="record-model-domxml-canonical-index"/> for
233 <section id="record-model-domxml-pipeline-store">
234 <title>Store pipeline</title>
235 The <literal><store></literal> pipeline takes documents
236 from any common &dom; &xml; format to the &zebra; specific
237 storage &dom; &xml; format.
238 It may consist of zero ore more
239 <literal><![CDATA[<xslt stylesheet="path/file.xsl"/>]]></literal>
240 &xslt; transformations, and the outcome is handled to the
241 &zebra; core for deposition into the internal storage system.
244 <section id="record-model-domxml-pipeline-retrieve">
245 <title>Retrieve pipeline</title>
247 Finally, there may be one or more
248 <literal><retrieve></literal> pipeline definitions, each
249 of them again consisting of zero or more
250 <literal><![CDATA[<xslt stylesheet="path/file.xsl"/>]]></literal>
251 &xslt; transformations. These are used for document
252 presentation after search, and take the internal storage &dom;
253 &xml; to the requested output formats during record present
257 The possible multiple
258 <literal><retrieve></literal> pipeline definitions
259 are distinguished by their unique <literal>name</literal>
260 attributes, these are the literal <literal>schema</literal> or
261 <literal>element set</literal> names used in
262 <ulink url="http://www.loc.gov/standards/sru/srw/">&srw;</ulink>,
263 <ulink url="&url.sru;">&sru;</ulink> and
264 &z3950; protocol queries.
269 <section id="record-model-domxml-canonical-index">
270 <title>Canonical Indexing Format</title>
273 &dom; &xml; indexing comes in two flavors: pure
274 processing-instruction governed plain &xml; documents, and - very
275 similar to the Alvis filter indexing format - &xml; documents
276 containing &xml; <literal><record></literal> and
277 <literal><index></literal> instructions from the magic
278 namespace <literal>xmlns:z="http://indexdata.dk/zebra-2.0"</literal>.
281 <section id="record-model-domxml-canonical-index-pi">
282 <title>Processing-instruction governed indexing format</title>
284 <para>The output of the processing instruction driven
285 indexing &xslt; stylesheets must contain
286 processing instructions named
287 <literal>zebra-2.0</literal>.
288 The output of the &xslt; indexing transformation is then
289 parsed using &dom; methods, and the contained instructions are
290 performed on the <emphasis>elements and their
291 subtrees directly following the processing instructions</emphasis>.
294 For example, the output of the command
296 xsltproc dom-index-pi.xsl marc-one.xml
298 might look like this:
301 <?xml version="1.0" encoding="UTF-8"?>
302 <?zebra-2.0 record id=11224466 rank=42?>
304 <?zebra-2.0 index control:0?>
305 <control>11224466</control>
306 <?zebra-2.0 index any:w title:w title:p title:s?>
307 <title>How to program a computer</title>
314 <section id="record-model-domxml-canonical-index-element">
315 <title>Magic element governed indexing format</title>
317 <para>The output of the indexing &xslt; stylesheets must contain
318 certain elements in the magic
319 <literal>xmlns:z="http://indexdata.dk/zebra-2.0"</literal>
320 namespace. The output of the &xslt; indexing transformation is then
321 parsed using &dom; methods, and the contained instructions are
322 performed on the <emphasis>magic elements and their
326 For example, the output of the command
328 xsltproc dom-index-element.xsl marc-one.xml
330 might look like this:
333 <?xml version="1.0" encoding="UTF-8"?>
334 <z:record xmlns:z="http://indexdata.com/zebra-2.0"
335 z:id="11224466" z:rank="42">
336 <z:index name="control:0">11224466</z:index>
337 <z:index name="any:w title:w title:p title:s">
338 How to program a computer</z:index>
346 <section id="record-model-domxml-canonical-index-semantics">
347 <title>Semantics of the indexing formats</title>
350 Both indexing formats are defined with equal semantics and
354 <para>&zebra; specific instructions are either
355 processing instructions named
356 <literal>zebra-2.0</literal> or
357 elements contained in the namespace
358 <literal>xmlns:z="http://indexdata.dk/zebra-2.0"</literal>.
362 <para>There must be exactly one <literal>record</literal>
363 instruction, which sets the scope for the following,
364 possibly nested <literal>index</literal> instructions.
368 <para>The unique <literal>record</literal> instruction
369 may have additional attributes <literal>id</literal> and
370 <literal>rank</literal>, where the value of the opaque ID
371 may be any string not containing the whitespace character
372 <literal>' '</literal>, and the rank value must be a
373 non-negative integer. See
374 <xref linkend="administration-ranking"/>
378 <para> Multiple and possible nested <literal>index</literal>
379 instructions must contain at least one
380 <literal>indexname:indextype</literal>
381 pair, and may contain multiple such pairs separated by the
382 whitespace character <literal>' '</literal>. In each index
383 pair, the name and the type of the index is separated by a
384 colon character <literal>':'</literal>.
389 Any index name consisting of ASCII letters, and following the
390 standard &zebra; rules will do, see
391 <xref linkend="querymodel-pqf-apt-mapping-accesspoint"/>.
396 Index types are restricted to the values defined in
397 the standard configuration
398 file <filename>default.idx</filename>, see
399 <xref linkend="querymodel-bib1"/> and
400 <xref linkend="fields-and-charsets"/> for details.
407 <para>The examples work as follows:
408 From the original &xml; file
409 <literal>marc-one.xml</literal> (or from the &xml; record &dom; of the
410 same form coming from an <literal><input></literal>
413 pipeline <literal><extract></literal>
414 produces an indexing &xml; record, which is defined by
415 the <literal>record</literal> instruction
416 &zebra; uses the content of
417 <literal>z:id="11224466"</literal>
419 <literal>id=11224466</literal>
421 record ID, and - in case static ranking is set - the content of
422 <literal>rank=42</literal>
424 <literal>z:rank="42"</literal>
429 <para>In these examples, the following literal indexes are constructed:
437 where the indexing type is defined after the
438 literal <literal>':'</literal> character.
439 Any value from the standard configuration
440 file <filename>default.idx</filename> will do.
442 <literal>text()</literal> node content recursively contained
443 inside the <literal><z:index></literal> element, or any
444 element following a <literal>index</literal> processing instruction,
445 will be filtered through the
446 appropriate char map for character normalization, and will be
447 inserted in the named indexes.
450 Finally, this example configuration can be queried using &pqf;
451 queries, either transported by &z3950;, (here using a yaz-client)
454 Z> open localhost:9999
458 Z> find @attr 1=control @attr 4=3 11224466
459 Z> scan @attr 1=control @attr 4=3 ""
461 Z> find @attr 1=title program
462 Z> scan @attr 1=title ""
464 Z> find @attr 1=title @attr 4=2 "How to program a computer"
465 Z> scan @attr 1=title @attr 4=2 ""
469 extensions <literal>x-pquery</literal> and
470 <literal>x-pScanClause</literal> to
474 http://localhost:9999/?version=1.1&operation=searchRetrieve&x-pquery=@attr 1=title program
475 http://localhost:9999/?version=1.1&operation=scan&x-pScanClause=@attr 1=title ""
478 See <xref linkend="zebrasrv-sru"/> for more information on &sru;/&srw;
479 configuration, and <xref linkend="gfs-config"/> or the &yaz;
480 <ulink url="&url.yaz.cql;">&cql; section</ulink>
481 for the details or the &yaz; frontend server.
484 Notice that there are no <filename>*.abs</filename>,
485 <filename>*.est</filename>, <filename>*.map</filename>, or other &grs1;
486 filter configuration files involves in this process, and that the
487 literal index names are used during search and retrieval.
490 In case that we want to support the usual
491 <literal>bib-1</literal> &z3950; numeric access points, it is a
492 good idea to choose string index names defined in the default
493 configuration file <filename>tab/bib1.att</filename>, see
494 <xref linkend="attset-files"/>
503 <section id="record-model-domxml-conf">
504 <title>&dom; Record Model Configuration</title>
507 <section id="record-model-domxml-index">
508 <title>&dom; Indexing Configuration</title>
510 As mentioned above, there can be only one indexing pipeline,
511 and configuration of the indexing process is a synonym
512 of writing an &xslt; stylesheet which produces &xml; output containing the
513 magic processing instructions or elements discussed in
514 <xref linkend="record-model-domxml-canonical-index"/>.
515 Obviously, there are million of different ways to accomplish this
516 task, and some comments and code snippets are in order to
520 Stylesheets can be written in the <emphasis>pull</emphasis> or
521 the <emphasis>push</emphasis> style: <emphasis>pull</emphasis>
522 means that the output &xml; structure is taken as starting point of
523 the internal structure of the &xslt; stylesheet, and portions of
524 the input &xml; are <emphasis>pulled</emphasis> out and inserted
525 into the right spots of the output &xml; structure.
527 side, <emphasis>push</emphasis> &xslt; stylesheets are recursively
528 calling their template definitions, a process which is commanded
529 by the input &xml; structure, and is triggered to produce
531 whenever some special conditions in the input stylesheets are
532 met. The <emphasis>pull</emphasis> type is well-suited for input
533 &xml; with strong and well-defined structure and semantics, like the
534 following &oai; indexing example, whereas the
535 <emphasis>push</emphasis> type might be the only possible way to
536 sort out deeply recursive input &xml; formats.
539 A <emphasis>pull</emphasis> stylesheet example used to index
540 &oai; harvested records could use some of the following template
544 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
545 xmlns:z="http://indexdata.dk/zebra-2.0"
546 xmlns:oai="http://www.openarchives.org/&oai;/2.0/"
547 xmlns:oai_dc="http://www.openarchives.org/&oai;/2.0/oai_dc/"
548 xmlns:dc="http://purl.org/dc/elements/1.1/"
551 <!-- Example pull and magic element style Zebra indexing -->
552 <xsl:output indent="yes" method="xml" version="1.0" encoding="UTF-8"/>
554 <!-- disable all default text node output -->
555 <xsl:template match="text()"/>
557 <!-- disable all default recursive element node transversal -->
558 <xsl:template match="node()"/>
560 <!-- match only on oai xml record root -->
561 <xsl:template match="/">
562 <z:record z:id="{normalize-space(oai:record/oai:header/oai:identifier)}">
563 <!-- you may use z:rank="{some XSLT; function here}" -->
565 <!-- explicetly calling defined templates -->
566 <xsl:apply-templates/>
570 <!-- OAI indexing templates -->
571 <xsl:template match="oai:record/oai:header/oai:identifier">
572 <z:index name="oai_identifier;0">
573 <xsl:value-of select="."/>
579 <!-- DC specific indexing templates -->
580 <xsl:template match="oai:record/oai:metadata/oai_dc:dc/dc:title">
581 <z:index name="dc_any:w dc_title:w dc_title:p dc_title:s ">
582 <xsl:value-of select="."/>
594 that the names and types of the indexes can be defined in the
595 indexing &xslt; stylesheet <emphasis>dynamically according to
596 content in the original &xml; records</emphasis>, which has
597 opportunities for great power and wizardry as well as grande
601 The following excerpt of a <emphasis>push</emphasis> stylesheet
602 <emphasis>might</emphasis>
603 be a good idea according to your strict control of the &xml;
604 input format (due to rigorous checking against well-defined and
605 tight RelaxNG or &xml; Schema's, for example):
608 <xsl:template name="element-name-indexes">
609 <z:index name="{name()}:w">
610 <xsl:value-of select="'1'"/>
615 This template creates indexes which have the name of the working
616 node of any input &xml; file, and assigns a '1' to the index.
618 <literal>find @attr 1=xyz 1</literal>
619 finds all files which contain at least one
620 <literal>xyz</literal> &xml; element. In case you can not control
621 which element names the input files contain, you might ask for
622 disaster and bad karma using this technique.
625 One variation over the theme <emphasis>dynamically created
626 indexes</emphasis> will definitely be unwise:
629 <!-- match on oai xml record root -->
630 <xsl:template match="/">
633 <!-- create dynamic index name from input content -->
634 <xsl:variable name="dynamic_content">
635 <xsl:value-of select="oai:record/oai:header/oai:identifier"/>
638 <!-- create zillions of indexes with unknown names -->
639 <z:index name="{$dynamic_content}:w">
640 <xsl:value-of select="oai:record/oai:metadata/oai_dc:dc"/>
647 Don't be tempted to play too smart tricks with the power of
648 &xslt;, the above example will create zillions of
649 indexes with unpredictable names, resulting in severe &zebra;
654 <section id="record-model-domxml-elementset">
655 <title>&dom; Exchange Formats</title>
657 An exchange format can be anything which can be the outcome of an
658 &xslt; transformation, as far as the stylesheet is registered in
659 the main &dom; &xslt; filter configuration file, see
660 <xref linkend="record-model-domxml-filter"/>.
661 In principle anything that can be expressed in &xml;, HTML, and
662 TEXT can be the output of a <literal>schema</literal> or
663 <literal>element set</literal> directive during search, as long as
664 the information comes from the
665 <emphasis>original input record &xml; &dom; tree</emphasis>
666 (and not the transformed and <emphasis>indexed</emphasis> &xml;!!).
669 In addition, internal administrative information from the &zebra;
670 indexer can be accessed during record retrieval. The following
671 example is a summary of the possibilities:
674 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
675 xmlns:z="http://indexdata.dk/zebra/xslt/1"
678 <!-- register internal zebra parameters -->
679 <xsl:param name="id" select="''"/>
680 <xsl:param name="filename" select="''"/>
681 <xsl:param name="score" select="''"/>
682 <xsl:param name="schema" select="''"/>
684 <xsl:output indent="yes" method="xml" version="1.0" encoding="UTF-8"/>
686 <!-- use then for display of internal information -->
687 <xsl:template match="/">
689 <id><xsl:value-of select="$id"/></id>
690 <filename><xsl:value-of select="$filename"/></filename>
691 <score><xsl:value-of select="$score"/></score>
692 <schema><xsl:value-of select="$schema"/></schema>
704 <section id="record-model-domxml-example">
705 <title>&dom; Filter &oai; Indexing Example</title>
707 The source code tarball contains a working &dom; filter example in
708 the directory <filename>examples/dom-oai/</filename>, which
709 should get you started.
712 More example data can be harvested from any &oai; compliant server,
713 see details at the &oai;
714 <ulink url="http://www.openarchives.org/">
715 http://www.openarchives.org/</ulink> web site, and the community
717 <ulink url="http://www.openarchives.org/community/index.html">
718 http://www.openarchives.org/community/index.html</ulink>.
721 <ulink url="http://www.oaforum.org/tutorial/">
722 http://www.oaforum.org/tutorial/</ulink>.
734 <!-- Keep this comment at the end of the file
739 sgml-minimize-attributes:nil
740 sgml-always-quote-attributes:t
743 sgml-parent-document: "zebra.xml"
744 sgml-local-catalogs: nil
745 sgml-namecase-general:t