1 <!doctype linuxdoc system>
4 $Id: zebra.sgml,v 1.24 1996-04-17 09:21:29 quinn Exp $
8 <title>Zebra Server - Administrators's Guide and Reference
9 <author><htmlurl url="http://www.indexdata.dk/" name="Index Data">, <tt><htmlurl url="mailto:info@index.ping.dk" name="info@index.ping.dk"></>
10 <date>$Revision: 1.24 $
12 The Zebra information server combines a versatile fielded/free-text
13 search engine with a Z39.50-1995 frontend to provide a powerful and flexible
14 information management system. This document explains the procedure for
15 installing and configuring the system, and outlines the possibilities
16 for managing data and providing Z39.50
17 services with the software.
27 The Zebra system is a fielded free-text indexing and retrieval engine with a
28 Z39.50 frontend. You can use any commercial or freeware Z39.50 client
29 to access data stored in Zebra.
31 The Zebra server is our first step towards the development of a fully
32 configurable, open information system. Eventually, it will be paired
33 off with a powerful Z39.50 client to support complex information
34 management tasks within almost any application domain. We're making
35 the server available now because it's no fun to be in the open
36 information retrieval business all by yourself. We want to allow
37 people with interesting data to make their things
38 available in interesting ways, without having to start out
39 by implementing yet another protocol stack from scratch.
41 This document is an introduction to the Zebra system. It will tell you
42 how to compile the software, and how to prepare your first database.
43 It also explains how the server can be configured to give you the
44 functionality that you need.
46 If you find the software interesting, you should join the support
47 mailing-list by sending Email to <tt/zebra-request@index.ping.dk/.
52 This is a listof some of the most important features of the
58 Supports updating - records can be added and deleted without
59 rebuilding the index from scratch.
60 The update procedure is tolerant to crashes or hard interrupts
61 during register updating - registers can be reconstructed following a crash.
62 Registers can be safely updated even while users are accessing the server.
65 Supports large databases - files for indices, etc. can be
66 automatically partitioned over multiple disks.
69 Supports arbitrarily complex records - base input format is an
70 SGML-like syntax which allows nested (structured) data elements, as
71 well as variant forms of data.
74 Supports boolean queries as well as relevance-ranking (free-text)
75 searching. Right truncation and masking in terms are supported, as
76 well as full regular expressions.
79 Supports multiple concrete syntaxes
80 for record exchange (depending on the configuration): GRS-1, SUTRS,
81 ISO2709 (*MARC). Records can be mapped between record syntaxes and
90 Protocol facilities: Init, Search, Retrieve, Browse.
93 Piggy-backed presents are honored in the search-request.
96 Named result sets are supported.
99 Easily configured to support different application profiles, with
100 tables for attribute sets, tag sets, and abstract syntaxes.
101 Additional tables control facilities such as element mappings to
102 different schema (eg., GILS-to-USMARC).
105 Complex composition specifications using Espec-1 are partially
106 supported (simple element requests only).
109 Element Set Names are defined using the Espec-1 capability of the
110 system, and are given in configuration files as simple element
111 requests (and possibly variant requests).
114 Some variant support (not fully implemented yet).
117 Using the YAZ toolkit for the protocol implementation, the
118 server can utilise a plug-in XTI/mOSI implementation (not included) to
119 provide SR services over an OSI stack, as well as Z39.50 over TCP/IP.
128 This is an alfa-release of the software, to allow you to look at
129 it - try it out, and assess whether it can be of use to you. We expect
130 this version to be followed by a succession of beta-releases until we
131 arrive at a stable first version.
133 These are some of the plans that we have for the software in the near
134 and far future, approximately ordered after their relative importance.
136 asterisk will be implemented before the
142 *Allow the system to handle other input formats. Specifically
143 MARC records and general, structured ASCII records (such as mail/news
144 files) parameterized by regular expressions.
147 *Complete the support for variants. Finalize support for the WAIS
148 retrieval methodology.
151 *Finalize the data element <it/include/ facility to support multimedia
152 data elements in records.
155 *Port the system to Windows NT.
158 Add index and data compression to save disk space.
161 Add more sophisticated relevance ranking mechanisms. Add support for soundex
162 and stemming. Add relevance feedback support.
168 Add support for very large records by implementing segmentation and/or
172 Support the Item Update extended service of the protocol.
175 The Zebra search engine supports approximate string matching in the
176 index. We'd like to find a way to support and control this from RPN.
179 We want to add a management system that allows you to
180 control your databases and configuration tables from a graphical
181 interface. We'll probably use Tcl/Tk to stay platform-independent.
185 Programmers thrive on user feedback. If you are interested in a facility that
186 you don't see mentioned here, or if there's something you think we
187 could do better, please drop us a mail. If you think it's all really
188 neat, you're welcome to drop us a line saying that, too. You'll find
189 contact info at the end of this file.
191 <sect>Compiling the software
194 An ANSI C compiler is required to compile the Zebra
195 server system — <tt/gcc/ works fine if your own system doesn't
196 provide an adequate compiler.
198 Unpack the distribution archive. In some cases, you may want to edit
199 the top-level <tt/Makefile/, eg. to select a different C compiler, or
200 to specify machine-specific libraries in the <bf/NETLIB/ variable.
202 When you are done editing the <tt>Makefile</tt> type:
207 If successful, two executables have been created in the sub-directory
210 <tag><tt>zebrasrv</tt></tag> The Z39.50 server and search engine.
211 <tag><tt>zebraidx</tt></tag> The administrative tool for the search index.
216 In this section, we will test the system by indexing a small set of sample
217 GILS records that are included with the software distribution. Go to the
218 <tt>test</tt> subdirectory of the distribution archive. There you will
220 file named <tt>zebra.cfg</tt> with the following contents:
222 # Where are the YAZ tables located.
223 profilePath: ../../yaz/tab ../tab
225 # Files that describe the attribute sets supported.
230 Now, edit the file and set <tt>profilePath</tt> to the path of the
231 YAZ profile tables (sub directory <tt>tab</tt> of the YAZ distribution
234 The 48 test records are located in the sub directory <tt>records</tt>.
235 To index these, type:
237 $ ../index/zebraidx -t grs update records
240 In the command above the option <tt>-t</tt> specified the record
241 type — in this case <tt>grs</tt>. The word <tt>update</tt> followed
242 by a directory root updates all files below that directory node.
244 If your indexing command was successful, you are now ready to
245 fire up a server. To start a server on port 2100, type:
247 $ ../index/zebrasrv tcp:@:2100
250 The Zebra index that you have just created has a single database
251 named <tt/Default/. The database contains records structured according to
252 the GILS profile, and the server will
253 return records in either either USMARC, GRS-1, or SUTRS depending
254 on what your client asks
257 To test the server, you can use any Z39.50 client (1992 or later). For
258 instance, you can use the demo client that comes with YAZ: Just cd to
259 the <tt/client/ subdirectory of the YAZ distribution and type:
262 $ client tcp:localhost:2100
265 When the client has connected, you can type:
272 The default retrieval syntax for the client is USMARC. To try other
273 formats for the same record, try:
284 <it>NOTE: You may notice that more fields are returned when your
285 client requests SUTRS or GRS-1 records. When retrieving GILS records,
286 this is normal - not all of the GILS data elements have mappings in
287 the USMARC record format.</it>
289 If you've made it this far, there's a good chance that
290 you've got through the compilation OK.
292 <sect>Administrating Zebra<label id="administrating">
295 Unlike many simpler retrieval systems, Zebra supports safe, incremental
296 updates to an existing index.
298 Normally, when Zebra modifies the index it reads a number of records
300 Depending on your specifications and on the contents of each record
301 one the following events take place for each record:
303 <tag>Insert</tag> The record is indexed as if it never occurred
304 before. Either the Zebra system doesn't know how to identify the record or
305 Zebra can identify the record but didn't find it to be already indexed.
306 <tag>Modify</tag> The record has already been indexed. In this case
307 either the contents of the record or the location (file) of the record
308 indicates that it has been indexed before.
309 <tag>Delete</tag> The record is deleted from the index. As in the
310 update-case it must be able to identify the record.
313 Please note that in both the modify- and delete- case the Zebra
314 indexer must be able to generate a unique key that identifies the record in
315 question (more on this below).
317 To administrate the Zebra retrieval system, you run the
318 <tt>zebraidx</tt> program. This program supports a number of options
319 which are preceded by a minus, and a few commands (not preceded by
322 Both the Zebra administrative tool and the Z39.50 server share a
323 set of index files and a global configuration file. The
324 name of the configuration file defaults to <tt>zebra.cfg</tt>.
325 The configuration file includes specifications on how to index
326 various kinds of records and where the other configuration files
327 are located. <tt>zebrasrv</tt> and <tt>zebraidx</tt> <em>must</em>
328 be run in the directory where the configuration file lives unless you
329 indicate the location of the configuration file by option
332 <sect1>Record Types<label id="record-types">
334 Indexing is a per-record process, in which
335 either insert/modify/delete will occur. Before a record is indexed
336 search keys are extracted from whatever might be the layout the
337 original record (sgml,html,text, etc..). The Zebra system
338 currently only supports SGML-like, structured records and unstructured text
340 To specify a particular extraction process, use either the
341 command line option <tt>-t</tt> or specify a
342 <tt>recordType</tt> setting in the configuration file.
344 <sect1>The Zebra Configuration File<label id="configuration-file">
346 The Zebra configuration file, read by <tt>zebraidx</tt> and
347 <tt>zebrasrv</tt> defaults to <tt>zebra.cfg</tt> unless specified
348 by <tt>-c</tt> option.
350 You can edit the configuration file with a normal text editor.
351 Parameter names and values are seperated by colons in the file. Lines
352 starting with a hash sign (<tt/#/) are treated as comments.
354 If you manage different sets of records that share common
355 characteristics, you can organize the configuration settings for each
356 type into &dquot;groups&dquot;.
357 When <tt>zebraidx</tt> is run and you wish to address a given group
358 you specify the group name with the <tt>-g</tt> option. In this case
359 settings that have the group name as their prefix will be used
360 by <tt>zebraidx</tt>. If no <tt/-g/ option is specified, the settings
361 with no prefix are used.
363 In the configuration file, the group name is placed before the option
365 itself, separated by a dot (.). For instance, to set the record type
366 for group <tt/public/ to <tt/grs/ (the common format for structured
367 records) you would write:
370 public.recordType: grs
373 To set the default value of the record type to <tt/text/ write:
379 The available configuration settings are summarized below. They will be
380 explained further in the following sections.
383 <tag><it>group</it>.recordType[<it>.name</it>]</tag>
384 Specifies how records with the file extension <it>name</it> should
385 be handled by the indexer. This option may also be specified
386 as a command line option (<tt>-t</tt>). Note that if you do not
387 specify a <it/name/, the setting applies to all files.
388 <tag><it>group</it>.recordId</tag>
389 Specifies how the records are to be identified when updated. See
390 section <ref id="locating-records" name="Locating Records">.
391 <tag><it>group</it>.database</tag>
392 Specifies the Z39.50 database name.
393 <tag><it>group</it>.storeKeys</tag>
394 Specifies whether key information should be saved for a given
395 group of records. If you plan to update/delete this type of
396 records later this should be specified as 1; otherwise it
397 should be 0 (default), to save register space. See section
398 <ref id="file-ids" name="Indexing With File Record IDs">.
399 <tag><it>group</it>.storeData</tag>
400 Specifies whether the records should be stored internally
401 in the Zebra system files. If you want to maintain the raw records yourself,
402 this option should be false (0). If you want Zebra to take care of the records
403 for you, it should be true(1).
405 Specifies the location of the various register files that Zebra uses
406 to represent your databases. See section
407 <ref id="register-location" name="Register Location">.
409 Enables the <it/safe update/ facility of Zebra, and tells the system
410 where to place the required, temporary files. See section
411 <ref id="shadow-registers" name="Safe Updating - Using Shadow Registers">.
413 Directory in which various lock files are stored.
414 <tag>tempSetPath</tag>
415 Specifies the directory that the server uses for temporary result sets.
416 If not specified <tt>/tmp</tt> will be used.
417 <tag>profilePath</tag>
418 Specifies the location of profile specification files.
420 Specifies the filename(s) of attribute set files for use in
421 searching. At least the Bib-1 set should be loaded (<tt/bib1.att/).
422 The <tt/profilePath/ setting is used to look for the specified files.
423 See section <ref id="attset-files" name="The Attribute Set Files">
426 <sect1>Locating Records<label id="locating-records">
428 The default behaviour of the Zebra system is to reference the
429 records from their original location, i.e. where they were found when you
430 ran <tt/zebraidx/. That is, when a client wishes to retrieve a record
431 following a search operation, the files are accessed from the place
432 where you originally put them - if you remove the files (without
433 running <tt/zebraidx/ again, the client will receive a diagnostic
436 If your input files are not permanent - for example if you retrieve
437 your records from an outside source, or if they were temporarily
438 mounted on a CD-ROM drive,
439 you may want Zebra to make an internal copy of them. To do this,
440 you specify 1 (true) in the <tt>storeData</tt> setting. When
441 the Z39.50 server retrieves the records they will be read from the
442 internal file structures of the system.
444 <sect1>Indexing with no Record IDs (Simple Indexing)
447 If you have a set of records that is not expected to change over time
448 you may can build your database without record IDs.
449 This indexing method uses less space than the other methods and
452 To use this method, you simply don't provide the <tt>recordId</tt> entry
453 for the group of files that you index. To add a set of records you use
454 <tt>zebraidx</tt> with the <tt>update</tt> command. The
455 <tt>update</tt> command will always add all of the records that it
456 encounters to the index - whether they have already been indexed or
457 not. If the set of indexed files change, you should delete all of the
458 index files, and build a new index from scratch.
460 Consider a system in which you have a group of text files called
461 <tt>simple</tt>. That group of records should belong to a Z39.50 database
462 called <tt>textbase</tt>. The following <tt/zebra.cfg/ file will suffice:
465 profilePath: /usr/local/yaz
467 simple.recordType: text
468 simple.database: textbase
471 Since the existing records in an index can not be addressed by their
472 IDs, it is impossible to delete or modify records when using this method.
474 <sect1>Indexing with File Record IDs<label id="file-ids">
477 If you have a set of files that regularly change over time: Old files
478 are deleted, new ones are added, or existing files are modified, you
479 can benefit from using the <it/file ID/ indexing methodology. Examples
480 of this type of database might include an index of WWW resources, or a
481 USENET news spool area. Briefly speaking, the file key methodology
482 uses the directory paths of the individual records as a unique
483 identifier for each record. To perform indexing of a directory with
484 file keys, again, you specify the top-level directory after the
485 <tt>update</tt> command. The command will recursively traverse the
486 directories and compare each one with whatever have been indexed before in
487 that same directory. If a file is new (not in the previous version of
488 the directory) it is inserted into the registers; if a file was
489 already indexed and it has been modified since the last update,
490 the index is also modified; if a file has been removed since the last
491 visit, it is deleted from the index.
493 The resulting system is easy to administrate. To delete a record you
494 simply have to delete the corresponding file (say, with the <tt/rm/
495 command). And to add records you create new files (or directories with
496 files). For your changes to take effect in the register you must run
497 <tt>zebraidx update</tt> with the same directory root again. This mode
498 of operation requires more disk space than simpler indexing methods,
499 but it makes it easier for you to keep the index in sync with a
500 frequently changing set of data. If you combine this system with the
501 <it/safe update/ facility (see below), you never have to take your
502 server offline for maintenance or register updating purposes.
504 To enable indexing with pathname IDs, you must specify <tt>file</tt> as
505 the value of <tt>recordId</tt> in the configuration file. In addition,
506 you should set <tt>storeKeys</tt> to <tt>1</tt>, since the Zebra
507 indexer must save additional information about the contents of each record
508 in order to modify the indices correctly at a later time.
510 For example, to update records of group <tt>esdd</tt> located below
511 <tt>/data1/records/</tt> you should type:
513 $ zebraidx -g esdd update /data1/records
516 The corresponding configuration file includes:
523 <em>Important note: You cannot start out with a group of records with simple
524 indexing (no record IDs as in the previous section) and then later
525 enable file record Ids. Zebra must know from the first time that you
527 the files should be indexed with file record IDs.
530 You cannot explicitly delete records when using this method (using the
531 <bf/delete/ command to <tt/zebraidx/. Instead
532 you have to delete the files from the file system (or move them to a
534 and then run <tt>zebraidx</tt> with the <bf/update/ command.
536 <sect1>Indexing with General Record IDs
538 When using this method you construct an (almost) arbritrary, internal
539 record key based on the contents of the record itself and other system
540 information. If you have a group of records that explicitly associates
541 an ID with each record, this method is convenient. For example, the
542 record format may contain a title or a ID-number - unique within the group.
543 In either case you specify the Z39.50 attribute set and use-attribute
544 location in which this information is stored, and the system looks at
545 that field to determine the identity of the record.
547 As before, the record ID is defined by the <tt>recordId</tt> setting
548 in the configuration file. The value of the record ID specification
549 consists of one or more tokens separated by whitespace. The resulting
551 represented in the index by concatenating the tokens and separating them by
554 There are three kinds of tokens:
556 <tag>Internal record info</tag> The token refers to a key that is
557 extracted from the record. The syntax of this token is
558 <tt/(/ <em/set/ <tt/,/ <em/use/ <tt/)/, where <em/set/ is the
559 attribute set ordinal number and <em/use/ is the use value of the attribute.
560 <tag>System variable</tag> The system variables are preceded by
561 <verb>$</verb> and immediately followed by the system variable name, which
564 <tag>group</tag> Group name.
565 <tag>database</tag> Current database specified.
566 <tag>type</tag> Record type.
568 <tag>Constant string</tag> A string used as part of the ID — surrounded
569 by single- or double quotes.
572 For instance, the sample GILS records that come with the Zebra
573 distribution contain a
575 in the Control-Identifier field. This field is mapped to the Bib-1
576 use attribute 1007. To use this field as a record id, specify
577 <tt>(1,1007)</tt> as the value of the <tt>recordId</tt> in the
578 configuration file. If you have other record types that uses
579 the same field for a different purpose, you might add the record type (or group or database name)
580 to the record id of the gils records as well, to prevent matches
581 with other types of records. In this case the recordId might be
584 gils.recordId: $type (1,1007)
587 (see section <ref id="data-model" name="Configuring Your Data Model">
588 for details of how the mapping between elements of your records and
589 searchable attributes is established).
591 As for the file record ID case described in the previous section,
592 updating your system is simply a matter of running <tt>zebraidx</tt>
593 with the <tt>update</tt> command. However, the update with general
594 keys is considerably slower than with file record IDs, since all files
595 visited must be (re)read to discover their IDs.
597 As you might expect, when using the general record IDs
598 method, you can only add or modify existing records with the <tt>update</tt>
599 command. If you wish to delete records, you must use the,
600 <tt>delete</tt> command, with a directory as a parameter.
601 This will remove all records that match the files below that root
604 <sect1>Register Location<label id="register-location">
607 Normally, the index files that form dictionaries, inverted
608 files, record info, etc., are stored in the directory where you run
609 <tt>zebraidx</tt>. If you wish to store these, possibly large, files
610 somewhere else, you must add the <tt>register</tt> entry to the
611 <tt/zebra.cfg/ file. Furthermore, the Zebra system allows its file
613 span multiple file systems, which is useful for managing very large
616 The value of the <tt>register</tt> setting is a sequence of tokens.
617 Each token takes the form:
619 <em>dir</em><tt>:</tt><em>size</em>.
621 The <em>dir</em> specifies a directory in which index files will be
622 stored and the <em>size</em> specifies the maximum size of all
623 files in that directory. The Zebra indexer system fills each directory
624 in the order specified and use the next specified directories as needed.
625 The <em>size</em> is an integer followed by a qualifier
626 code, <tt>M</tt> for megabytes, <tt>k</tt> for kilobytes.
628 For instance, if you have allocated two disks for your register, and
629 the first disk is mounted
630 on <tt>/d1</tt> and has 200 Mb of free space and the
631 second, mounted on <tt>/d2</tt> has 300 Mb, you could
632 put this entry in your configuration file:
634 register: /d1:200M /d2:300M
637 Note that Zebra does not verify that the amount of space specified is
638 actually available on the directory (file system) specified - it is
639 your responsibility to ensure that enough space is available, and that
640 other applications do not attempt to use the free space. In a large production system,
641 it is recommended that you allocate one or more filesystem exclusively
642 to the Zebra register files.
644 <sect1>Safe Updating - Using Shadow Registers<label id="shadow-registers">
649 The Zebra server supports <it/updating/ of the index structures. That is,
650 you can add, modify, or remove records from databases managed by Zebra
651 without rebuilding the entire index. Since this process involves
652 modifying structured files with various references between blocks of
653 data in the files, the update process is inherently sensitive to
654 system crashes, or to process interruptions: Anything but a
655 successfully completed update process will leave the register files in
656 an unknown state, and you will essentially have no recourse but to
657 re-index everything, or to restore the register files from a backup
658 medium. Further, while the update process is active, users cannot be
659 allowed to access the system, as the contents of the register files
660 may change unpredictably.
662 You can solve these problems by enabling the shadow register system in
663 Zebra. During the updating procedure, <tt/zebraidx/ will temporarily
664 write changes to the involved files in a set of &dquot;shadow
665 files&dquot;, without modifying the files that are accessed by the
666 active server processes. If the update procedure is interrupted by a
667 system crash or a signal, you simply repeat the procedure - the
668 register files have not been changed or damaged, and the partially
669 written shadow files are automatically deleted before the new updating
672 At the end of the updating procedure (or in a separate operation, if
673 you so desire), the system enters a &dquot;commit mode&dquot;. First,
674 any active server processes are forced to access those blocks that
675 have been changed from the shadow files rather than from the main
676 register files; the unmodified blocks are still accessed at their
677 normal location (the shadow files are not a complete copy of the
678 register files - they only contain those parts that have actually been
679 modified). If the commit process is interrupted at any point during the
680 commit process, the server processes will continue to access the
681 shadow files until you can repeat the commit procedure and complete
682 the writing of data to the main register files. You can perform
683 multiple update operations to the registers before you commit the
684 changes to the system files, or you can execute the commit operation
685 at the end of each update operation. When the commit phase has
686 completed successfully, any running server processes are instructed to
687 switch their operations to the new, operational register, and the
688 temporary shadow files are deleted.
690 <sect2>How to Use Shadow Register Files
693 The first step is to allocate space on your system for the shadow
694 files. You do this by adding a <tt/shadow/ entry to the <tt/zebra.cfg/
695 file. The syntax of the <tt/shadow/ entry is exactly the same as for
696 the <tt/register/ entry (see section <ref name="Register Location"
697 id="register-location">). The location of the shadow area should be
698 <it/different/ from the location of the main register area (if you
699 have specified one - remember that if you provide no <tt/register/
700 setting, the default register area is the
701 working directory of the server and indexing processes).
703 The following excerpt from a <tt/zebra.cfg/ file shows one example of
704 a setup that configures both the main register location and the shadow
705 file area. Note that two directories or partitions have been set aside
706 for the shadow file area. You can specify any number of directories
707 for each of the file areas, but remember that there should be no
708 overlaps between the directories used for the main registers and the
709 shadow files, respectively.
714 shadow: /scratch1:100M /scratch2:200M
717 When shadow files are enabled, an extra command is available at the
718 <tt/zebraidx/ command line. In order to make changes to the system
719 take effect for the users, you'll have to submit a
720 &dquot;commit&dquot; command after a (sequence of) update
721 operation(s). You can ask the indexer to commit the changes
722 immediately after the update operation:
725 $ zebraidx update /d1/records update /d2/more-records commit
728 Or you can execute multiple updates before committing the changes:
731 $ zebraidx -g books update /d1/records update /d2/more-records
732 $ zebraidx -g fun update /d3/fun-records
736 If one of the update operations above had been interrupted, the commit
737 operation on the last line would fail: <tt/zebraidx/ will not let you
738 commit changes that would destroy the running register. You'll have to
739 rerun all of the update operations since your last commit operation,
740 before you can commit the new changes.
742 Similarly, if the commit operation fails, <tt/zebraidx/ will not let
743 you start a new update operation before you have successfully repeated
744 the commit operation. The server processes will keep accessing the
745 shadow files rather than the (possibly damaged) blocks of the main
746 register files until the commit operation has successfully completed.
748 You should be aware that update operations may take slightly longer
749 when the shadow register system is enabled, since more file access
750 operations are involved. Further, while the disk space required for
751 the shadow register data is modest for a small update operation, you
752 may prefer to disable the system if you are adding a very large number
753 of records to an already very large database (we use the terms
754 <it/large/ and <it/modest/ very loosely here, since every
755 application will have a different perception of size). To update the system
756 without the use of the the shadow files, simply run <tt/zebraidx/ with
757 the <tt/-n/ option (note that you do not have to execute the
758 <bf/commit/ command of <tt/zebraidx/ when you temporarily disable the
759 use of the shadow registers in this fashion. Note also that, just as
760 when the shadow registers are not enabled, server processes will be
761 barred from accessing the main register while the update procedure
764 <sect>Running the Maintenance Interface (zebraidx)
767 The following is a complete reference to the command line interface to
768 the <tt/zebraidx/ application.
772 $ zebraidx [options] command [directory] ...
776 <tag>-t <it/type/</tag>Update all files as <it/type/. Currently, the
777 types supported are <tt/text/ and <tt/grs/<it/.filter/. If no
778 <it/filter/ is provided for the GRS (General Record Structure) type,
779 the canonical input format is assumed (see section <ref
780 id="local-representation" name="Local Representation">). Generally, it
781 is probably advisable to specify the record types in the
782 <tt/zebra.cfg/ file (see section <ref id="record-types" name="Record Types">).
784 <tag>-c <it/config-file/</tag>Read the configuration file
785 <it/config-file/ instead of <tt/zebra.cfg/.
787 <tag>-g <it/group/</tag>Update the files according to the group
788 settings for <it/group/ (see section <ref id="configuration-file"
789 name="The Zebra Configuration File">).
791 <tag>-d <it/database/</tag>The records located should be associated
792 with the database name <it/database/ for access through the Z39.50
795 <tag>-d <it/mbytes/</tag>Use <it/mbytes/ of megabytes before flushing
796 keys to background storage. This setting affects performance when
797 updating large databases.
799 <tag>-n</tag>Disable the use of shadow registers for this operation
800 (see section <ref id="shadow-registers" name="Robust Updating - Using
803 <tag>-v <it/level/</tag>Set the log level to <it/level/. <it/level/
804 should be one of <tt/none/, <tt/debug/, and <tt/all/.
810 <tag>Update <it/directory/</tag>Update the register with the files
811 contained in <it/directory/. If no directory is provided, a list of
812 files is read from <tt/stdin/. See section <ref
813 id="administrating" name="Administrating Zebra">.
815 <tag>Delete <it/directory/</tag>Remove the records corresponding to
816 the files found under <it/directory/ from the register.
818 <tag/Commit/Write the changes resulting from the last <bf/update/
819 commands to the register. This command is only available if the use of
820 shadow register files is enabled (see section <ref
821 id="shadow-registers" name="Robust Updating - Using Shadow
826 <sect>Running the Z39.50 Server (zebrasrv)
831 zebrasrv [options] [listener-address ...]
836 <tag>-a <it/APDU file/</tag> Specify a file for dumping PDUs (for diagnostic purposes).
837 The special name &dquot;-&dquot; sends output to <tt/stderr/.
839 <tag>-c <it/config-file/</tag> Read configuration information from <it/config-file/. The default configuration is <tt>./zebra.cfg</tt>.
841 <tag/-S/Don't fork on connection requests. This can be useful for
842 symbolic-level debugging. The server can only accept a single
843 connection in this mode.
845 <tag/-s/Use the SR protocol.
847 <tag/-z/Use the Z39.50 protocol (default). These two options complement
848 eachother. You can use both multiple times on the same command
849 line, between listener-specifications (see below). This way, you
850 can set up the server to listen for connections in both protocols
851 concurrently, on different local ports.
853 <tag>-l <it/logfile/</tag>Specify an output file for the diagnostic
854 messages. The default is to write this information to <tt/stderr/.
856 <tag>-v <it/log-level/</tag>The log level. Use a comma-separated list of members of the set
857 {fatal,debug,warn,log,all,none}.
859 <tag>-u <it/username/</tag>Set user ID. Sets the real UID of the server process to that of the
860 given <it/username/. It's useful if you aren't comfortable with having the
861 server run as root, but you need to start it as such to bind a
864 <tag>-w <it/working-directory/</tag>Change working directory.
866 <tag/-i/Run under the Internet superserver, <tt/inetd/.
869 A <it/listener-address/ consists of a transport mode followed by a
870 colon (:) followed by a listener address. The transport mode is
871 either <tt/osi/ or <tt/tcp/.
873 For TCP, an address has the form
876 hostname | IP-number [: portnumber]
879 The port number defaults to 210 (standard Z39.50 port).
881 For OSI (only available if the server is compiled with XTI/mOSI
882 support enabled), the address form is
885 [t-selector /] hostname | IP-number [: portnumber]
888 The transport selector is given as a string of hex digits (with an even
889 number of digits). The default port number is 102 (RFC1006 port).
897 osi:0402/dbserver.osiworld.com:3000
901 In both cases, the special hostname &dquot;@&dquot; is mapped to
902 the address INADDR_ANY, which causes the server to listen on any local
903 interface. To start the server listening on the registered ports for
904 Z39.50 and SR over OSI/RFC1006, and to drop root privileges once the
905 ports are bound, execute the server like this (from a root shell):
908 zebrasrv -u daemon tcp:@ -s osi:@
911 You can replace <tt/daemon/ with another user, eg. your own account, or
912 a dedicated IR server account.
914 The default behavior for <tt/zebrasrv/ is to establish a single TCP/IP
915 listener, for the Z39.50 protocol, on port 9999.
917 <sect>The Record Model
920 The Zebra system is designed to support a wide range of data management
921 applications. The system can be configured to handle virtually any
922 kind of structured data. Each record in the system is associated with
923 a <it/record schema/ which lends context to the data elements of the
924 record. Any number of record schema can coexist in the system.
925 Although it may be wise to use only a single schema within
926 one database, the system poses no such restrictions.
928 Records pass through three different states during processing in the
932 <item>When records are accessed by the system, they are represented
933 in their local, or native format. This might be SGML or HTML files,
934 News or Mail archives, MARC records. If the system doesn't already
935 know how to read the type of data you need to store, you can set up an
936 input filter by preparing conversion rules based on regular
937 expressions and a flexible scripting language (Tcl). The input filter
938 produces as output an internal representation:
940 <item>When records are processed by the system, they are represented
941 in a tree-structure, constructed by tagged data elements hanging off a
942 root node. The tagged elements may contain data or yet more tagged
943 elements in a recursive structure. The system performs various
944 actions on this tree structure (indexing, element selection, schema
947 <item>Before transmitting records to the client, they are first
948 converted from the internal structure to a form suitable for exchange
949 over the network - according to the Z39.50 standard.
952 <sect1>Local Representation<label id="local-representation">
955 As mentioned earlier, Zebra places few restrictions on the type of
956 data that you can index and manage. Generally, whatever the form of
957 the data, it is parsed by an input filter specific to that format, and
958 turned into an internal structure that Zebra knows how to handle. This
959 process takes place whenever the record is accessed - for indexing and
962 <sect2>Canonical Input Format
965 Although input data can take any form, it is sometimes useful to
966 describe the record processing capabilities of the system in terms of
967 a single, canonical input format that gives access to the full
968 spectrum of structure and flexibility in the system. In Zebra, this
969 canonical format is an &dquot;SGML-like&dquot; syntax.
971 Consider a record describing an information resource (such a record is
972 sometimes known as a <it/locator record/). It might contain a field
973 describing the distributor of the information resource, which might in
974 turn be partitioned into various fields providing details about the
975 distributor, like this:
979 <Name> USGS/WRD &etago;Name>
980 <Organization> USGS/WRD &etago;Organization>
982 U.S. GEOLOGICAL SURVEY, 505 MARQUETTE, NW
983 &etago;Street-Address>
984 <City> ALBUQUERQUE &etago;City>
985 <State> NM &etago;State>
986 <Zip-Code> 87102 &etago;Zip-Code>
987 <Country> USA &etago;Country>
988 <Telephone> (505) 766-5560 &etago;Telephone>
992 <it>NOTE: The indentation used above is used to illustrate how Zebra
993 interprets the markup. The indentation, in itself, has no
994 significance to the parser for the canonical input format, which
995 discards superfluous whitespace.</it>
997 The keywords surrounded by <...> are <it/tags/, while the
998 sections of text in between are the <it/data elements/. A data element
999 is characterized by its location in the tree that is made up by the
1000 nested elements. Each element is terminated by a closing tag -
1001 beginning with &etago;, and containing the same symbolic tag-name as
1002 the corresponding opening tag. The general closing tag - &etago;> -
1003 terminates the element started by the last opening tag. The
1004 structuring of elements is significant. The element <bf/Telephone/,
1005 for instance, may be indexed and presented to the client differently,
1006 depending on whether it appears inside the <bf/Distributor/ element,
1007 or some other, structured data element such a <bf/Supplier/ element.
1012 The first tag in a record describes the root node of the tree that
1013 makes up the total record. In the canonical input format, the root tag
1014 should contain the name of the schema that lends context to the
1015 elements of the record (see section <ref id="internal-representation"
1016 name="Internal Representation">). The following is a GILS record that
1017 contains only a single element (strictly speaking, that makes it an
1018 illegal GILS record, since the GILS profile includes several mandatory
1019 elements - Zebra does not validate the contents of a record against
1020 the Z39.50 profile, however - it merely attempts to match up elements
1021 of a local representation with the given schema):
1025 <title>Zen and the Art of Motorcycle Maintenance&etago;title>
1032 Zebra allows you to provide individual data elements in a number of
1033 <it/variant forms/. Examples of variant forms are textual data
1034 elements which might appear in different languages, and images which
1035 may appear in different formats or layouts. The variant system in
1037 essentially a representation of the variant mechanism of
1040 The following is an example of a title element which occurs in two
1041 different languages.
1045 <var lang lang "eng">
1046 Zen and the Art of Motorcycle Maintenance&etago;>
1047 <var lang lang "dan">
1048 Zen og Kunsten at Vedligeholde en Motorcykel&etago;>
1052 The syntax of the <it/variant element/ is <tt><<bf/var/ <it/class
1053 type value/></tt>. The available values for the <it/class/ and
1054 <it/type/ fields are given by the variant set that is associated with the
1055 current schema (see section <ref id="variant-set" name="Variant Set
1058 Variant elements are terminated by the general end-tag &etago;>, by
1059 the variant end-tag &etago;var>, by the appearance of another variant
1060 tag with the same <it/class/ and <it/value/ settings, or by the
1061 appearance of another, normal tag. In other words, the end-tags for
1062 the variants used in the example above could have been saved.
1064 Variant elements can be nested. The element
1068 <var lang lang "eng"><var body iana "text/plain">
1069 Zen and the Art of Motorcycle Maintenance
1073 Associates two variant components to the variant list for the title
1076 Given the nesting rules described above, we could write
1080 <var body iana "text/plain>
1081 <var lang lang "eng">
1082 Zen and the Art of Motorcycle Maintenance
1083 <var lang lang "dan">
1084 Zen og Kunsten at Vedligeholde en Motorcykel
1088 The title element above comes in two variants. Both have the IANA body
1089 type &dquot;text/plain&dquot;, but one is in English, and the other in
1090 Danish. The client, using the element selection mechanism of Z39.50,
1091 can retrieve information about the available variant forms of data
1092 elements, or it can select specific variants based on the requirements
1095 <sect2>Input Filters
1098 In order to handle general input formats, Zebra allows the
1099 operator to define filters which read individual records in their native format
1100 and produce an internal representation that the system can
1103 Input filters are ASCII files, generally with the suffix <tt/.flt/.
1104 The system looks for the files in the directories given in the
1105 <bf/profilePath/ setting in the <tt/zebra.cfg/ file.
1107 Generally, an input filter consists of a sequence of rules, where each
1108 rule consists of a sequence of expressions, followed by an action. The
1109 expressions are evaluated against the contents of the input record,
1110 and the actions normally contribute to the generation of an internal
1111 representation of the record.
1113 An expression can be either of the following:
1116 <tag/INIT/The action associated with this expression is evaluated
1117 exactly once in the lifetime of the application, before any records
1118 are read. It can be used in conjunction with an action that
1119 initializes tables or other resources that are used in the processing
1122 <tag/BEGIN/Matches the beginning of the record. It can be used to
1123 initialize variables, etc. Typically, the <bf/BEGIN/ rule is also used
1124 to establish the root node of the record.
1126 <tag/END/Matches the end of the record - when all of the contents
1127 of the record has been processed.
1129 <tag>/pattern/</tag>Matches a string of characters from the input
1132 <tag/BODY/This keyword may only be used between two patterns. It
1133 matches everything between (not including) those patterns.
1135 <tag/FINISH/THe expression asssociated with this pattern is evaluated
1136 once, before the application terminates. It can be used to release
1137 system resources - typically ones allocated in the <bf/INIT/ step.
1141 An action is surrounded by curly braces ({...}), and consists of a
1142 sequence of statements. Statements may be separated by newlines or
1143 semicolons (;). Within actions, the strings that matched the
1144 expressions immediately preceding the action can be referred to as
1145 $0, $1, $2, etc.
1147 The available statements are:
1151 <tag>begin <it/type [parameter ... ]/</tag>Begin a new
1152 data element. The type is one of the following:
1154 <tag/record/Begin a new record. The followingparameter should be the
1155 name of the schema that describes the structure of the record, eg.
1156 <tt/gils/ or <tt/wais/ (see below). The <tt/begin record/ call should
1158 any other use of the <bf/begin/ statement.
1160 <tag/element/Begin a new tagged element. The parameter is the
1161 name of the tag. If the tag is not matched anywhere in the tagsets
1162 referenced by the current schema, it is treated as a local string
1165 <tag/variant/Begin a new node in a variant tree. The parameters are
1166 <it/class type value/.
1170 <tag/data/Create a data element. The concatenated arguments make
1171 up the value of the data element. The option <tt/-text/ signals that
1172 the layout (whitespace) of the data should be retained for
1173 transmission. The option <tt/-element/ <it/tag/ wraps the data up in
1174 the <it/tag/. The use of the <tt/-element/ option is equivalent to
1175 preceding the command with a <bf/begin element/ command, and following
1176 it with the <bf/end/ command.
1178 <tag>end <it/[type]/</tag>Close a tagged element. If no parameter is given,
1179 the last element on the stack is terminated. The first parameter, if
1180 any, is a type name, similar to the <bf/begin/ statement. For the
1181 <bf/element/ type, a tag name can be provided to terminate a specific tag.
1185 The following input filter reads a Usenet news file, producing a
1186 record in the WAIS schema. Note that the body of a news posting is
1187 separated from the list of headers by a blank line (or rather a
1188 sequence of two newline characters.
1191 BEGIN { begin record wais }
1193 /^From:/ BODY /$/ { data -element name $1 }
1194 /^Subject:/ BODY /$/ { data -element title $1 }
1195 /^Date:/ BODY /$/ { data -element lastModified $1 }
1197 begin element bodyOfDisplay
1198 begin variant body iana "text/plain"
1204 If Zebra is compiled with support for Tcl (Tool Command Language)
1205 enabled, the statements described above are supplemented with a complete
1206 scripting environment, including control structures (conditional
1207 expressions and loop constructs), and powerful string manipulation
1208 mechanisms for modifying the elements of a record. Tcl is a popular
1209 scripting environment, with several tutorials available both online
1212 <it>NOTE: Tcl support is not currently available, but will be
1213 included with one of the next alpha or beta releases.</it>
1215 <it>NOTE: Variant support is not currently available in the input
1216 filter, but will be included with one of the next alpha or beta
1219 <sect1>Internal Representation<label id="internal-representation">
1222 When records are manipulated by the system, they're represented in a
1223 tree-structure, with data elements at the leaf nodes, and tags or
1224 variant components at the non-leaf nodes. The root-node identifies the
1225 schema that lends context to the tagging and structuring of the
1226 record. Imagine a simple record, consisting of a 'title' element and
1227 an 'author' element:
1230 TITLE "Zen and the Art of Motorcycle Maintenance"
1232 AUTHOR "Robert Pirsig"
1235 A slightly more complex record would have the author element consist
1236 of two elements, a surname and a first name:
1239 TITLE "Zen and the Art of Motorcycle Maintenance"
1246 The root of the record will refer to the record schema that describes
1247 the structuring of this particular record. The schema defines the
1248 element tags (TITLE, FIRST-NAME, etc.) that may occur in the record, as
1249 well as the structuring (SURNAME should appear below AUTHOR, etc.). In
1250 addition, the schema establishes element set names that are used by
1251 the client to request a subset of the elements of a given record. The
1252 schema may also establish rules for converting the record to a
1253 different schema, by stating, for each element, a mapping to a
1256 <sect2>Tagged Elements
1259 A data element is characterized by its tag, and its position in the
1260 structure of the record. For instance, while the tag &dquot;telephone
1261 number&dquot; may be used different places in a record, we may need to
1262 distinguish between these occurrences, both for searching and
1263 presentation purposes. For instance, while the phone numbers for the
1264 &dquot;customer&dquot; and the &dquot;service provider&dquot; are both
1265 representatives for the same type of resource (a telephone number), it
1266 is essential that they be kept separate. The record schema provides
1267 the structure of the record, and names each data element (defined by
1268 the sequence of tags - the tag path - by which the element can be
1269 reached from the root of the record).
1274 The children of a tag node may be either more tag nodes, a data node
1275 (possibly accompanied by tag nodes),
1276 or a tree of variant nodes. The children of variant nodes are either
1277 more variant nodes or a data node (possibly accompanied by more
1278 variant nodes). Each leaf node, which is normally a
1279 data node, corresponds to a <it/variant form/ of the tagged element
1280 identified by the tag which parents the variant tree. The following
1281 title element occurs in two different languages:
1284 VARIANT LANG=ENG "War and Peace"
1286 VARIANT LANG=DAN "Krig og Fred"
1289 Which of the two elements are transmitted to the client by the server
1290 depends on the specifications provided by the client, if any.
1292 In practice, each variant node is associated with a triple of class,
1293 type, value, corresponding to the variant mechanism of Z39.50.
1295 <sect2>Data Elements
1298 Data nodes have no children (they are always leaf nodes in the record
1301 <it>NOTE: Documentation needs extension here about types of nodes - numerical,
1302 textual, etc., plus the various types of inclusion notes.</it>
1304 <sect1>Configuring Your Data Model<label id="data-model">
1307 The following sections describe the configuration files that govern
1308 the internal management of data records. The system searches for the files
1309 in the directories specified by the <bf/profilePath/ setting in the
1310 <tt/zebra.cfg/ file.
1312 <sect2>The Abstract Syntax
1315 The abstract syntax definition (also known as an Abstract Record
1316 Structure, or ARS) is the focal point of the
1317 record schema description. For a given schema, the ABS file may state any
1318 or all of the following:
1321 <item>The object identifier of the Z39.50 schema associated
1322 with the ARS, so that it can be referred to by the client.
1324 <item>The attribute set (which can possibly be a compound of multiple
1325 sets) which applies in the profile. This is used when indexing and
1326 searching the records belonging to the given profile.
1328 <item>The Tag set (again, this can consist of several different sets).
1329 This is used when reading the records from a file, to recognize the
1330 different tags, and when transmitting the record to the client -
1331 mapping the tags to their numerical representation, if they are
1334 <item>The variant set which is used in the profile. This provides a
1335 vocabulary for specifying the <it/forms/ of data that appear inside
1338 <item>Element set names, which are a shorthand way for the client to
1339 ask for a subset of the data elements contained in a record. Element
1340 set names, in the retrieval module, are mapped to <it/element
1341 specifications/, which contain information equivalent to the
1342 <it/Espec-1/ syntax of Z39.50.
1344 <item>Map tables, which may specify mappings to <it/other/ database
1345 profiles, if desired.
1347 <item>Possibly, a set of rules describing the mapping of elements to a
1348 MARC representation.
1350 <item>A list of element descriptions (this is the actual ARS of the
1351 schema, in Z39.50 terms), which lists the ways in which the various
1352 tags can be used and organized hierarchically.
1355 Several of the entries above simply refer to other files, which
1356 describe the given objects.
1358 <sect2>The Configuration Files
1361 This section describes the syntax and use of the various tables which
1362 are used by the retrieval module.
1364 The number of different file types may appear daunting at first, but
1365 each type corresponds fairly clearly to a single aspect of the Z39.50
1366 retrieval facilities. Further, the average database administrator,
1367 who is simply reusing an existing profile for which tables already
1368 exist, shouldn't have to worry too much about the contents of these tables.
1370 Generally, the files are simple ASCII files, which can be maintained
1371 using any text editor. Blank lines, and lines beginning with a (#) are
1372 ignored. Any characters on a line followed by a (#) are also ignored.
1374 lines contain <it/directives/, which provide some setting or value
1375 to the system. Generally, settings are characterized by a single
1376 keyword, identifying the setting, followed by a number of parameters.
1377 Some settings are repeatable (r), while others may occur only once in a
1378 file. Some settings are optional (o), whicle others again are
1381 <sect2>The Abstract Syntax (.abs) Files
1384 The name of this file type is slightly misleading in Z39.50 terms,
1385 since, apart from the actual abstract syntax of the profile, it also
1386 includes most of the other definitions that go into a database
1389 When a record in the canonical, SGML-like format is read from a file
1390 or from the database, the first tag of the file should reference the
1391 profile that governs the layout of the record. If the first tag of the
1392 record is, say, <tt><gils></tt>, the system will look for the profile
1393 definition in the file <tt/gils.abs/. Profile definitions are cached,
1394 so they only have to be read once during the lifespan of the current
1397 When writing your own input filters, the <bf/record-begin/ command
1398 introduces the profile, and should always be called first thing when
1399 introducing a new record.
1401 The file may contain the following directives:
1404 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1405 description for the profile. Mostly useful for diagnostic purposes.
1407 <tag>reference <it/OID-name/</tag> (m) The reference name of the OID for
1408 the profile. The reference names can be found in the <bf/util/
1411 <tag>attset <it/filename/</tag> (m) The attribute set that is used for
1412 indexing and searching records belonging to this profile.
1414 <tag>tagset <it/filename/</tag> (o) The tag set (if any) that describe
1415 that fields of the records.
1417 <tag>varset <it/filename/</tag> (o) The variant set used in the profile.
1419 <tag>maptab <it/filename/</tag> (o,r) This points to a
1420 conversion table that might be used if the client asks for the record
1421 in a different schema from the native one.
1423 <tag>marc <it/filename/</tag> (o) Points to a file containing parameters
1424 for representing the record contents in the ISO2709 syntax. Read the
1425 description of the MARC representation facility below.
1427 <tag>esetname <it/name filename/</tag> (o,r) Associates the
1428 given element set name with an element selection file. If an (@) is
1429 given in place of the filename, this corresponds to a null mapping for
1430 the given element set name.
1432 <tag>elm <it/path name attribute/</tag> (o,r) Adds an element
1433 to the abstract record syntax of the schema. The <it/path/ follows the
1434 syntax which is suggested by the Z39.50 document - that is, a sequence
1435 of tags separated by slashes (/). Each tag is given as a
1436 comma-separated pair of tag type and -value surrounded by parenthesis.
1437 The <it/name/ is the name of the element, and the <it/attribute/
1438 specifies what attribute to use when indexing the element. A ! in
1439 place of the attribute name is equivalent to specifying an attribute
1440 name identical to the element name. A - in place of the attribute name
1441 specifies that no indexing is to take place for the given element.
1445 NOTE: The mechanism for controlling indexing is not adequate for
1446 complex databases, and will probably be moved into a separate
1447 configuration table eventually.
1450 The following is an excerpt from the abstract syntax file for the GILS
1455 reference GILS-schema
1460 maptab gils-usmarc.map
1464 esetname VARIANT gils-variant.est # for WAIS-compliance
1465 esetname B gils-b.est
1466 esetname G gils-g.est
1471 elm (1,14) localControlNumber Local-number
1472 elm (1,16) dateOfLastModification Date/time-last-modified
1474 elm (4,1) controlIdentifier Identifier-standard
1475 elm (2,6) abstract Abstract
1476 elm (4,51) purpose !
1477 elm (4,52) originator -
1478 elm (4,53) accessConstraints !
1479 elm (4,54) useConstraints !
1480 elm (4,70) availability -
1481 elm (4,70)/(4,90) distributor -
1482 elm (4,70)/(4,90)/(2,7) distributorName !
1483 elm (4,70)/(4,90)/(2,10 distributorOrganization !
1484 elm (4,70)/(4,90)/(4,2) distributorStreetAddress !
1485 elm (4,70)/(4,90)/(4,3) distributorCity !
1488 <sect2>The Attribute Set (.att) Files<label id="attset-files">
1491 This file type describes the <bf/Use/ elements of an attribute set.
1492 It contains the following directives.
1496 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1497 description for the attribute set. Mostly useful for diagnostic purposes.
1499 <tag>reference <it/OID-name/</tag> (m) The reference name of the OID for
1500 the attribute set. The reference names can be found in the <bf/util/
1503 <tag>ordinal <it/integer/</tag> (m) This value will be used to represent the
1504 attribute set in the index. Care should be taken that each attribute
1505 set has a unique ordinal value.
1507 <tag>include <it/filename/</tag> (o,r) This directive is used to
1508 include another attribute set as a part of the current one. This is
1509 used when a new attribute set is defined as an extension to another
1510 set. For instance, many new attribute sets are defined as extensions
1511 to the <bf/bib-1/ set. This is an important feature of the retrieval
1512 system of Z39.50, as it ensures the highest possible level of
1513 interoperability, as those access points of your database which are
1514 derived from the external set (say, bib-1) can be used even by clients
1515 who are unaware of the new set.
1517 <tag>att <it/att-value att-name [local-value]/</tag> (o,r) This
1518 repeatable directive introduces a new attribute to the set. The
1519 attribute value is stored in the index (unless a <it/local-value/ is
1520 given, in which case this is stored). The name is used to refer to the
1521 attribute from the <it/abstract syntax/. </descrip>
1523 This is an excerpt from the GILS attribute set definition. Notice how
1524 the file describing the <it/bib-1/ attribute set is referenced.
1528 reference GILS-attset
1532 att 2001 distributorName
1533 att 2002 indexTermsControlled
1535 att 2004 accessConstraints
1536 att 2005 useConstraints
1539 <sect2>The Tag Set (.tag) Files
1542 This file type defines the tagset of the profile, possibly by
1543 referencing other tag sets (most tag sets, for instance, will include
1544 tagsetG and tagsetM from the Z39.50 specification. The file may
1545 contain the following directives.
1548 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1549 description for the tag set. Mostly useful for diagnostic purposes.
1551 <tag>reference <it/OID-name/</tag> (o) The reference name of the OID for
1552 the tag set. The reference names can be found in the <bf/util/
1553 module of <bf/YAZ/. The directive is optional, since not all tag sets
1554 are registered outside of their schema.
1556 <tag>type <it/integer/</tag> (m) The type number of the tag within the schema
1559 <tag>include <it/filename/</tag> (o,r) This directive is used
1560 to include the definitions of other tag sets into the current one.
1562 <tag>tag <it/number names type/</tag> (o,r) Introduces a new
1563 tag to the set. The <it/number/ is the tag number as used in the protocol
1564 (there is currently no mechanism for specifying string tags at this
1565 point, but this would be quick work to add). The <it/names/ parameter
1566 is a list of names by which the tag should be recognized in the input
1567 file format. The names should be separated by slashes (/). The
1568 <it/type/ is th recommended datatype of the tag. It should be one of
1576 <item>generalizedtime
1584 The following is an excerpt from the TagsetG definition file.
1593 tag 3 publicationPlace string
1594 tag 4 publicationDate string
1595 tag 5 documentId string
1596 tag 6 abstract string
1598 tag 8 date generalizedtime
1599 tag 9 bodyOfDisplay string
1600 tag 10 organization string
1603 <sect2>The Variant Set (.var) Files<label id="variant-set">
1606 The variant set file is a straightforward representation of the
1607 variant set definitions associated with the protocol. At present, only
1608 the <it/Variant-1/ set is known.
1610 These are the directives allowed in the file.
1613 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1614 description for the variant set. Mostly useful for diagnostic purposes.
1616 <tag>reference <it/OID-name/</tag> (o) The reference name of the OID for
1617 the variant set, if one is required. The reference names can be found
1618 in the <bf/util/ module of <bf/YAZ/.
1620 <tag>class <it/integer class-name/</tag> (m,r) Introduces a new
1621 class to the variant set.
1623 <tag>type <it/integer type-name datatype/</tag> (m,r) Addes a
1624 new type to the current class (the one introduced by the most recent
1625 <bf/class/ directive). The type names belong to the same name space as
1626 the one used in the tag set definition file.
1629 The following is an excerpt from the file describing the variant set
1638 type 1 variantId octetstring
1643 type 2 z39.50 string
1647 <sect2>The Element Set (.est) Files
1650 The element set specification files describe a selection of a subset
1651 of the elements of a database record. The element selection mechanism
1652 is equivalent to the one supplied by the <it/Espec-1/ syntax of the
1653 Z39.50 specification. In fact, the internal representation of an
1654 element set specification is identical to the <it/Espec-1/ structure,
1655 and we'll refer you to the description of that structure for most of
1656 the detailed semantics of the directives below.
1659 NOTE: Not all of the Espec-1 functionality has been implemented yet.
1660 The fields that are mentioned below all work as expected, unless
1664 The directives available in the element set file are as follows:
1667 <tag>defaultVariantSetId <it/OID-name/</tag> (o) If variants are used in
1668 the following, this should provide the name of the variantset used
1669 (it's not currently possible to specify a different set in the
1670 individual variant request). In almost all cases (certainly all
1671 profiles known to us), the name <tt/Variant-1/ should be given here.
1673 <tag>defaultVariantRequest <it/variant-request/</tag> (o) This directive
1674 provides a default variant request for
1675 use when the individual element requests (see below) do not contain a
1676 variant request. Variant requests consist of a blank-separated list of
1677 variant components. A variant compont is a comma-separated,
1678 parenthesized triple of variant class, type, and value (the two former
1679 values being represented as integers). The value can currently only be
1680 entered as a string (this will change to depend on the definition of
1681 the variant in question). The special value (@) is interpreted as a
1682 null value, however.
1684 <tag>simpleElement <it/path ['variant' variant-request]/</tag>
1685 (o,r) This corresponds to a simple element request in <it/Espec-1/. The
1686 path consists of a sequence of tag-selectors, where each of these can
1690 <item>A simple tag, consisting of a comma-separated type-value pair in
1691 parenthesis, possibly followed by a colon (:) followed by an
1692 occurrences-specification (see below). The tag-value can be a number
1693 or a string. If the first character is an apostrophe ('), this forces
1694 the value to be interpreted as a string, even if it appears to be numerical.
1696 <item>A WildThing, represented as a question mark (?), possibly
1697 followed by a colon (:) followed by an occurrences specification (see
1700 <item>A WildPath, represented as an asterisk (*). Note that the last
1701 element of the path should not be a wildPath (wildpaths don't work in
1705 The occurrences-specification can be either the string <tt/all/, the
1706 string <tt/last/, or an explicit value-range. The value-range is
1707 represented as an integer (the starting point), possibly followed by a
1708 plus (+) and a second integer (the number of elements, default being
1711 The variant-request has the same syntax as the defaultVariantRequest
1712 above. Note that it may sometimes be useful to give an empty variant
1713 request, simply to disable the default for a specific set of fields
1714 (we aren't certain if this is proper <it/Espec-1/, but it works in
1715 this implementation).
1718 The following is an example of an element specification belonging to
1722 simpleelement (1,10)
1723 simpleelement (1,12)
1725 simpleelement (1,14)
1727 simpleelement (4,52)
1730 <sect2>The Schema Mapping (.map) Files<label id="schema-mapping">
1733 Sometimes, the client might want to receive a database record in
1734 a schema that differs from the native schema of the record. For
1735 instance, a client might only know how to process WAIS records, while
1736 the database record is represented in a more specific schema, such as
1737 GILS. In this module, a mapping of data to one of the MARC formats is
1738 also thought of as a schema mapping (mapping the elements of the
1739 record into fields consistent with the given MARC specification, prior
1740 to actually converting the data to the ISO2709). This use of the
1741 object identifier for USMARC as a schema identifier represents an
1742 overloading of the OID which might not be entirely proper. However,
1743 it represents the dual role of schema and record syntax which
1744 is assumed by the MARC family in Z39.50.
1747 NOTE: The schema-mapping functions are so far limited to a
1748 straightforward mapping of elements. This should be extended with
1749 mechanisms for conversions of the element contents, and conditional
1750 mappings of elements based on the record contents.
1753 These are the directives of the schema mapping file format:
1756 <tag>targetName <it/name/</tag> (m) A symbolic name for the target schema
1757 of the table. Useful mostly for diagnostic purposes.
1759 <tag>targetRef <it/OID-name/</tag> (m) An OID name for the target schema.
1760 This is used, for instance, by a server receiving a request to present
1761 a record in a different schema from the native one. The name, again,
1762 is found in the <bf/oid/ module of <bf/YAZ/.
1764 <tag>map <it/element-name target-path/</tag> (o,r) Adds
1765 an element mapping rule to the table.
1768 <sect2>The MARC (ISO2709) Representation (.mar) Files
1771 This file provides rules for representing a record in the ISO2709
1772 format. The rules pertain mostly to the values of the constant-length
1773 header of the record.
1775 <it>NOTE: This will be described better. We're in the process of
1776 re-evaluating and most likely changing the way that MARC records are
1777 handled by the system.</it>
1779 <sect1>Exchange Formats
1782 Converting records from the internal structure to en exchange format
1783 is largely an automatic process. Currently, the following exchange
1784 formats are supported:
1787 <item>GRS-1. The internal representation is based on GRS-1, so the
1788 conversion here is straightforward. The system will create
1789 applied variant and supported variant lists as required, if a record
1790 contains variant information.
1792 <item>SUTRS. Again, the mapping is fairly straighforward. Indentation
1793 is used to show the hierarchical structure of the record.
1795 <item>ISO2709-based formats (USMARC, etc.). Only records with a
1796 two-level structure (corresponding to fields and subfields) can be
1797 directly mapped to ISO2709. For records with a different structuring
1798 (eg., GILS), the representation in a structure like USMARC involves a
1799 schema-mapping (see section <ref id="schema-mapping" name="Schema
1800 Mapping">), to an &dquot;implied&dquot; USMARC schema (implied,
1801 because there is no formal schema which specifies the use of the
1802 USMARC fields outside of ISO2709). The resultant, two-level record is
1803 then mapped directly from the internal representation to ISO2709. See
1804 the GILS schema definition files for a detailed example of this
1807 <item>Explain. This representation is only available for records
1808 belonging to the Explain schema.
1815 Copyright © 1995, Index Data.
1817 All rights reserved.
1819 Use and redistribution in source or binary form, with or without
1820 modification, of any or all of this software and documentation is
1821 permitted, provided that the following conditions are met:
1823 1. This copyright and permission notice appear with all copies of the
1824 software and its documentation. Notices of copyright or attribution
1825 which appear at the beginning of any file must remain unchanged.
1827 2. The names of Index Data or the individual authors may not be used to
1828 endorse or promote products derived from this software without specific
1829 prior written permission.
1831 3. Source code or binary versions of this software and its
1832 documentation may be used freely in not-for-profit applications. For
1833 profit applications - such as providing for-pay database services,
1834 marketing a product based in whole or in part on this software or its
1835 documentation, or generally distributing this software or its
1836 documentation under a different license - requires a commercial
1837 license from Index Data. The software may be installed and used for
1838 evaluation purposes in conjunction with a commercial application for a
1839 trial period of no more than 60 days.
1841 THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
1842 EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
1843 WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
1844 IN NO EVENT SHALL INDEX DATA BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
1845 INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES
1846 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR
1847 NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
1848 LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
1851 <sect>About Index Data and the Zebra Server
1854 Index Data is a consulting and software-development enterprise that
1855 specialises in library and information management systems. Our
1856 interests and expertise span a broad range of related fields, and one
1857 of our primary, long-term objectives is the development of a powerful
1858 information management
1859 system with open network interfaces and hypermedia capabilities.
1861 We make this software available free of charge for not-for-profit
1862 purposes, as a service to the networking community, and to further
1863 the development and use of quality software for open network
1866 If you like this software, and would like to use all or part of it in
1867 a commercial product, or to provide a commercial database service,
1868 please contact us to discuss the details. We'll be happy to answer
1869 questions about the software, and about our services in general. If
1870 you have specific requirements to the software, we'll be glad to offer
1871 our advice - and if you need to adapt the software to a special
1872 purpose, our consulting services and expert knowledge of the software
1873 is available to you at favorable rates.
1878 DK-2200 København N&nl
1883 Phone: +45 3536 3672
1885 Email: info@index.ping.dk
1888 The <it>Random House College Dictionary</it>, 1975 edition
1889 offers this definition of the
1890 word &dquot;Zebra&dquot;:
1893 Zebra, n., any of several horselike, African mammals of the genus Equus,
1894 having a characteristic pattern of black or dark-brown stripes on
1895 a whitish background.