1 <chapter id="examples">
2 <!-- $Id: examples.xml,v 1.10 2002-10-17 08:10:08 mike 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>-t</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:../../../yaz/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>
129 <idzebra xmlns="http://www.indexdata.dk/zebra/">
130 <size>593</size>
131 <localnumber>891</localnumber>
132 <filename>records/genera.xml</filename>
138 Now wasn't that easy?
143 <sect1 id="example2">
144 <title>Example 2: Supporting Interoperable Searches</title>
147 The problem with the previous example is that you need to know the
148 structure of the documents in order to find them. For example,
149 when we wanted to know the genera for which Matt Wedel is an
150 author, we had to formulate a complex XPath
151 <literal>1=/GENUS/SPECIES/AUTHOR/@name</literal>
152 which embodies the knowledge that author names are specified in the
153 <literal>name</literal> attribute of the
154 <literal><AUTHOR></literal> element,
156 <literal><SPECIES></literal> element,
157 which in turn is inside the top-level
158 <literal><GENUS></literal> element.
161 This is bad not just because it requires a lot of typing, but more
162 significantly because it ties searching semantics to the physical
163 structure of the searched records. You can't use the same search
164 specification to search two databases if their internal
165 representations are different. Consider an alternative dinosaur
166 database in which the records have author names specified
167 inside an <literal><authorName></literal> element directly
168 inside a top-level <literal><taxon></literal> element: then
169 you'd need to search for them using
170 <literal>1=/taxon/authorName</literal>
173 How, then, can we build broadcasting Information Retrieval
174 applications that look for records in many different databases?
175 The Z39.50 protocol offers a powerful and general solution to this:
176 abstract ``access points''. In the Z39.50 model, an access point
177 is simply a point at which searches can be directed. Nothing is
178 said about implementation: in a given database, an access point
179 might be implemented as an index, a path into physical records, an
180 algorithm for interrogating relational tables or whatever works.
181 The key point is that the semantics of an access point are fixed
185 For convenience, access points are gathered into <firstterm>attribute
186 sets</firstterm>. For example, the BIB-1 attribute set is supposed to
187 contain bibliographic access points such as author, title, subject
188 and ISBN; the GEO attribute set contains access points pertaining
189 to geospatial information (bounding box, ###, etc.); the CIMI
190 attribute set contains access points to do with museum collections
191 (provenance, inscriptions, etc.)
194 In practice, the BIB-1 attribute set has tended to be a dumping
195 ground for all sorts of access points, so that, for example, it
196 includes some geospatial access points as well as strictly
197 bibliographic ones. Nevertheless, the key point is that this model
198 allows a layer of abstraction over the physical representation of
199 records in databases.
202 In the BIB-1 attribute set, an author search is represented by
203 access point 1003. (See
204 <ulink url="###bib1-semantics"/>)
205 So we need to configure our dinosaur database so that searches for
206 BIB-1 access point 1003 look the
207 <literal>name</literal> attribute of the
208 <literal><AUTHOR></literal> element,
210 <literal><SPECIES></literal> element,
212 <literal><GENUS></literal> element.
215 This is a two-step process. First, we need to tell Zebra that we
216 want to support the BIB-1 attribute set. Then we need to tell it
217 which elements of its record pertain to access point 1003.
236 You may have noticed as <literal>zebraidx</literal> was building
237 the database that it issued a warning, which we ignored at the
240 $ zebraidx update records
241 00:45:46-08/10: ../../index/zebraidx(5016) [warn] records/genera.xml:0 Couldn't open GENUS.abs [No such file or directory]
243 FIXME ### This needs more text
251 The master configuration file, <literal>zebra.cfg</literal>,
252 which is as short and simple as it can be:
254 # $Header: /home/cvsroot/idis/doc/examples.xml,v 1.10 2002-10-17 08:10:08 mike Exp $
255 # Bare-bones master configuration file for Zebra
256 profilePath: .:../../tab:../../../yaz/tab
258 Apart from the comments, which are ignored, all this specifies is
259 that the server should recognise the attribute set described in
261 <literal>bib1.att</literal>.
262 ### What is an attribute set?
268 The simplest hello-world example could go like this:
273 <title>The art of motorcycle maintenance</title>
274 <subject scheme="Dewey">zen</subject>
279 f @attr 1=/book/title motorcycle
281 f @attr 1=/book/subject[@scheme=Dewey] zen
283 If you suddenly decide you want broader interop, you can add
284 an abs file (more or less like this):
289 elm (2,1) title title
290 elm (2,21) subject subject
294 How to include images:
298 <imagedata fileref="system.eps" format="eps">
301 <imagedata fileref="system.gif" format="gif">
304 <phrase>The Multi-Lingual Search System Architecture</phrase>
308 <emphasis role="strong">
309 The Multi-Lingual Search System Architecture.
312 Network connections across local area networks are
313 represented by straight lines, and those over the
314 internet by jagged lines.
318 Whene the three <*object> thingies inside the top-level <mediaobject>
319 are decreasingly preferred version to include depending on what the
320 rendering engine can handle. I generated the EPS version of the image
321 by exporting a line-drawing done in TGIF, then converted that to the
322 GIF using a shell-script called "epstogif" which used an appallingly
323 baroque sequence of conversions, which I would prefer not to pollute
324 the Zebra build environment with:
328 # Yes, what follows is stupidly convoluted, but I can't find a
329 # more straightforward path from the EPS generated by tgif's
330 # "Print" command into a browser-friendly format.
332 file=`echo "$1" | sed 's/\.eps//'`
333 ps2pdf "$1" "$file".pdf
334 pdftopbm "$file".pdf "$file"
335 pnmscale 0.50 < "$file"-000001.pbm | pnmcrop | ppmtogif
336 rm -f "$file".pdf "$file"-000001.pbm
340 <!-- Keep this comment at the end of the file
345 sgml-minimize-attributes:nil
346 sgml-always-quote-attributes:t
349 sgml-parent-document: "zebra.xml"
350 sgml-local-catalogs: nil
351 sgml-namecase-general:t