1 <chapter id="examples">
2 <!-- $Id: examples.xml,v 1.15 2002-10-30 14:45:42 adam Exp $ -->
3 <title>Example Configurations</title>
6 <title>Overview</title>
9 <literal>zebraidx</literal> and <literal>zebrasrv</literal> are both
10 driven by a master configuration file, which may refer to other
11 subsidiary configuration files. By default, they try to use
12 <filename>zebra.cfg</filename> in the working directory as the
13 master file; but this can be changed using the <literal>-c</literal>
14 option to specify an alternative master configuration file.
17 The master configuration file tells Zebra:
22 Where to find subsidiary configuration files, including
23 <literal>default.idx</literal>
24 which specifies the default indexing rules.
30 What attribute sets to recognise in searches.
36 Policy details such as what record type to expect, what
37 low-level indexing algorithm to use, how to identify potential
38 duplicate records, etc.
45 Now let's see what goes in the <literal>zebra.cfg</literal> file
46 for some example configurations.
51 <title>Example 1: XML Indexing And Searching</title>
54 This example shows how Zebra can be used with absolutely minimal
55 configuration to index a body of
56 <ulink url="http://www.w3.org/xml/###">XML</ulink>
57 documents, and search them using
58 <ulink url="http://www.w3.org/xpath/###">XPath</ulink>
59 expressions to specify access points.
62 Go to the <literal>examples/dinosauricon</literal> subdirectory
63 of the distribution archive.
64 There you will find a <literal>records</literal> subdirectory,
65 which contains some raw XML data to be added to the database: in
66 this case, as single file, <literal>genera.xml</literal>,
67 which contain information about all the known dinosaur genera as of
71 Now we need to create the Zebra database, which we do with the
72 Zebra indexer, <literal>zebraidx</literal>, which is
73 driven by the <literal>zebra.cfg</literal> configuration file.
74 For our purposes, we don't need any
75 special behaviour - we can use the defaults - so we start with a
76 minimal file that just tells <literal>zebraidx</literal> where to
77 find the default indexing rules, and how to parse the records:
79 profilePath: .:../../tab
84 That's all you need for a minimal Zebra configuration. Now you can
85 roll the XML records into the database and build the indexes:
87 zebraidx update records
91 Now start the server. Like the indexer, its behaviour is
93 <literal>zebra.cfg</literal> file; and like the indexer, it works
94 just fine with this minimal configuration.
98 By default, the server listens on IP port number 9999, although
99 this can easily be changed - see
100 <xref linkend="zebrasrv"/>.
103 Now you can use the Z39.50 client program of your choice to execute
104 XPath-based boolean queries and fetch the XML records that satisfy
107 $ yaz-client tcp:@:9999
109 Z> find @attr 1=/GENUS/SPECIES/AUTHOR/@name Wedel
113 <GENUS name="Sauroposeidon" type="with">
114 <MEANING>lizard Poseidon <LOW>(Greek god of, among other things, earthquakes)</LOW></MEANING>
115 <SPECIES name="proteles">
116 <AUTHOR type="vide" name="Franklin" year="2000"></AUTHOR>
117 <AUTHOR name="Wedel, Cifelli, Sanders"></AUTHOR>
119 <PLACE name="Oklahoma"></PLACE>
120 <TIME value="Albian"></TIME>
121 <LENGTH value="30" q="1"></LENGTH>
122 <REMAINS content="rib, cervical vertebrae"></REMAINS>
124 <P> This new <NOMEN name="Brachiosaurus"></NOMEN>-like <LINK content="dinosaur"></LINK>
125 was perhaps the tallest. With its head raised, it stood 60 feet (nearly
126 20 m) tall. </P>
128 <idzebra xmlns="http://www.indexdata.dk/zebra/">
129 <size>593</size>
130 <localnumber>891</localnumber>
131 <filename>records/genera.xml</filename>
137 Now wasn't that easy?
142 <sect1 id="example2">
143 <title>Example 2: Supporting Interoperable Searches</title>
146 The problem with the previous example is that you need to know the
147 structure of the documents in order to find them. For example,
148 when we wanted to know the genera for which Matt Wedel is an
150 (<foreignphrase role="taxon">Sauroposeidon proteles</foreignphrase>),
151 we had to formulate a complex XPath
152 <literal>1=/GENUS/SPECIES/AUTHOR/@name</literal>
153 which embodies the knowledge that author names are specified in the
154 <literal>name</literal> attribute of the
155 <literal><AUTHOR></literal> element,
157 <literal><SPECIES></literal> element,
158 which in turn is inside the top-level
159 <literal><GENUS></literal> element.
162 This is bad not just because it requires a lot of typing, but more
163 significantly because it ties searching semantics to the physical
164 structure of the searched records. You can't use the same search
165 specification to search two databases if their internal
166 representations are different. Consider an alternative dinosaur
167 database in which the records have author names specified
168 inside an <literal><authorName></literal> element directly
169 inside a top-level <literal><taxon></literal> element: then
170 you'd need to search for them using
171 <literal>1=/taxon/authorName</literal>
174 How, then, can we build broadcasting Information Retrieval
175 applications that look for records in many different databases?
176 The Z39.50 protocol offers a powerful and general solution to this:
177 abstract ``access points''. In the Z39.50 model, an access point
178 is simply a point at which searches can be directed. Nothing is
179 said about implementation: in a given database, an access point
180 might be implemented as an index, a path into physical records, an
181 algorithm for interrogating relational tables or whatever works.
182 The key point is that the semantics of an access point are fixed
186 For convenience, access points are gathered into <firstterm>attribute
187 sets</firstterm>. For example, the BIB-1 attribute set is supposed to
188 contain bibliographic access points such as author, title, subject
189 and ISBN; the GEO attribute set contains access points pertaining
190 to geospatial information (bounding box, ###, etc.); the CIMI
191 attribute set contains access points to do with museum collections
192 (provenance, inscriptions, etc.)
195 In practice, the BIB-1 attribute set has tended to be a dumping
196 ground for all sorts of access points, so that, for example, it
197 includes some geospatial access points as well as strictly
198 bibliographic ones. Nevertheless, the key point is that this model
199 allows a layer of abstraction over the physical representation of
200 records in databases.
203 In the BIB-1 attribute set, an author search is represented by
204 access point 1003. (See
205 <ulink url="###bib1-semantics"/>)
206 So we need to configure our dinosaur database so that searches for
207 BIB-1 access point 1003 look the
208 <literal>name</literal> attribute of the
209 <literal><AUTHOR></literal> element,
211 <literal><SPECIES></literal> element,
213 <literal><GENUS></literal> element.
216 This is a two-step process. First, we need to tell Zebra that we
217 want to support the BIB-1 attribute set. Then we need to tell it
218 which elements of its record pertain to access point 1003.
221 We need to create an <link linkend="abs-file">Abstract Syntax
222 file</link> named after the document element of the records we're
223 working with, plus a <literal>.abs</literal> suffix - in this case,
224 <literal>GENUS.abs</literal> - as follows:
242 The simplest hello-world example could go like this:
247 <title>The art of motorcycle maintenance</title>
248 <subject scheme="Dewey">zen</subject>
253 f @attr 1=/book/title motorcycle
255 f @attr 1=/book/subject[@scheme=Dewey] zen
257 If you suddenly decide you want broader interop, you can add
258 an abs file (more or less like this):
263 elm (2,1) title title
264 elm (2,21) subject subject
268 How to include images:
272 <imagedata fileref="system.eps" format="eps">
275 <imagedata fileref="system.gif" format="gif">
278 <phrase>The Multi-Lingual Search System Architecture</phrase>
282 <emphasis role="strong">
283 The Multi-Lingual Search System Architecture.
286 Network connections across local area networks are
287 represented by straight lines, and those over the
288 internet by jagged lines.
292 Where the three <*object> thingies inside the top-level <mediaobject>
293 are decreasingly preferred version to include depending on what the
294 rendering engine can handle. I generated the EPS version of the image
295 by exporting a line-drawing done in TGIF, then converted that to the
296 GIF using a shell-script called "epstogif" which used an appallingly
297 baroque sequence of conversions, which I would prefer not to pollute
298 the Zebra build environment with:
302 # Yes, what follows is stupidly convoluted, but I can't find a
303 # more straightforward path from the EPS generated by tgif's
304 # "Print" command into a browser-friendly format.
306 file=`echo "$1" | sed 's/\.eps//'`
307 ps2pdf "$1" "$file".pdf
308 pdftopbm "$file".pdf "$file"
309 pnmscale 0.50 < "$file"-000001.pbm | pnmcrop | ppmtogif
310 rm -f "$file".pdf "$file"-000001.pbm
314 <!-- Keep this comment at the end of the file
319 sgml-minimize-attributes:nil
320 sgml-always-quote-attributes:t
323 sgml-parent-document: "zebra.xml"
324 sgml-local-catalogs: nil
325 sgml-namecase-general:t