1 <!doctype linuxdoc system>
4 $Id: zebra.sgml,v 1.14 1996-01-10 14:42:21 quinn Exp $
8 <title>Zebra Server - Administrators's Guide and Reference
9 <author><htmlurl url="http://130.225.252.168/" name="Index Data">, <tt><htmlurl url="mailto:info@index.ping.dk" name="info@index.ping.dk"></>
10 <date>$Revision: 1.14 $
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 Zebra uses the YAZ package to implement Z39.50, so you
195 have to compile YAZ before going further. Specifically, Zebra uses
196 the YAZ header files in <tt>yaz/include/..</tt> and its public library
197 <tt>yaz/lib/libyaz.a</tt>.
199 As with YAZ, an ANSI C compiler is required in order to compile the Zebra
200 server system — <tt/gcc/ works fine if your own system doesn't
201 provide an adequate compiler.
203 Unpack the Zebra software. You might put Zebra in the same directory level
204 as YAZ, for example if YAZ is placed in ..<tt>/src/yaz-xxx</tt>, then
205 Zebra is placed in ..<tt>/src/zebra-yyy</tt>.
207 Edit the top-level <tt>Makefile</tt> in the Zebra directory in which
208 you specify the location of YAZ by setting make variables.
209 The <tt>OSILIB</tt> should be empty if YAZ wasn't compiled with
210 MOSI support. Some systems, such as Solaris, have separate socket
211 libraries and for those systems you need to specify the
212 <tt>NETLIB</tt> variable.
214 When you are done editing the <tt>Makefile</tt> type:
219 If successful, two executables have been created in the sub-directory
222 <tag><tt>zebrasrv</tt></tag> The Z39.50 server and search engine.
223 <tag><tt>zebraidx</tt></tag> The administrative tool for the search index.
229 This section will get you started quickly! We will try to index a few sample
230 GILS records that are included with the Zebra distribution. Go to the
231 <tt>test</tt> subdirectory. There you will find a configuration
232 file named <tt>zebra.cfg</tt> with the following contents:
234 # Where are the YAZ tables located.
235 profilePath: /usr/local/yaz
237 # Files that describe the attribute sets supported.
242 Now, edit the file and set <tt>profilePath</tt> to the path of the
243 YAZ profile tables (sub directory <tt>tab</tt> of YAZ).
245 The 48 test records are located in the sub directory <tt>records</tt>.
246 To index these, type:
248 $ ../index/zebraidx -t grs update records
251 In the command above the option <tt>-t</tt> specified the record
252 type — in this case <tt>grs</tt>. The word <tt>update</tt> followed
253 by a directory root updates all files below that directory node.
255 If your indexing command was successful, you are now ready to
256 fire up a server. To start a server on port 2100, type:
258 $ ../index/zebrasrv tcp:@:2100
261 The Zebra index that you've just made has one database called Default. It will
262 return either USMARC, GRS-1, or SUTRS depending on what your client asks
265 To test the server, you can use any Z39.50 client (1992 or later). For
266 instance, you can use the demo client that comes with YAZ: Just cd to
267 the <tt/client/ subdirectory of the YAZ distribution and type:
270 $ client tcp:localhost:2100
273 When the client has connected, you can type:
280 The default retrieval syntax for the client is USMARC. To try other
281 formats for the same record, try:
290 If you've made it this far, there's a reasonably good chance that
291 you've got through the compilation OK.
293 <sect>Administrating Zebra<label id="administrating">
296 Unlike many simpler retrieval systems, Zebra supports safe, incremental
297 updates to an existing index.
299 Normally, when Zebra modifies the index it reads a number of records
301 Depending on your specifications and on the contents of each record
302 one the following events take place for each record:
304 <tag>Insert</tag> The record is indexed as if it never occurred
305 before. Either the Zebra system doesn't know how to identify the record or
306 Zebra can identify the record but didn't find it to be already indexed.
307 <tag>Modify</tag> The record has already been indexed. In this case
308 either the contents of the record or the location (file) of the record
309 indicates that it has been indexed before.
310 <tag>Delete</tag> The record is deleted from the index. As in the
311 update-case it must be able to identify the record.
314 Please note that in both the modify- and delete- case the Zebra
315 indexer must be able to generate a unique key that identifies the record in
316 question (more on this below).
318 To administrate the Zebra retrieval system, you run the
319 <tt>zebraidx</tt> program. This program supports a number of options
320 which are preceded by a minus, and a few commands (not preceded by
323 Both the Zebra administrative tool and the Z39.50 server share a
324 set of index files and a global configuration file. The
325 name of the configuration file defaults to <tt>zebra.cfg</tt>.
326 The configuration file includes specifications on how to index
327 various kinds of records and where the other configuration files
328 are located. <tt>zebrasrv</tt> and <tt>zebraidx</tt> <em>must</em>
329 be run in the same directory where the configuration file if you do
330 not indicate the location of the configuration file by option
333 <sect1>Record Types<label id="record-types">
335 Indexing is a per-record process, in which
336 either insert/modify/delete will occur. Before a record is indexed
337 search keys are extracted from whatever might be the layout the
338 original record (sgml,html,text, etc..). The Zebra system
339 currently only supports SGML-like, structured records and unstructured text
341 To specify a particular extraction process, use either the
342 command line option <tt>-t</tt> or specify a
343 <tt>recordType</tt> setting in the configuration file.
345 <sect1>The Zebra Configuration File<label id="configuration-file">
347 The Zebra configuration file, read by <tt>zebraidx</tt> and
348 <tt>zebrasrv</tt> defaults to <tt>zebra.cfg</tt> unless specified
349 by <tt>-c</tt> option.
351 You can edit the configuration file with a normal text editor.
352 Parameter names and values are seperated by colons in the file. Lines
353 starting with a hash sign (<tt/#/) are treated as comments.
355 If you manage different sets of records that each share common
356 caracteristics, you can organize the configuration settings for each
357 type into &dquot;groups&dquot;.
358 When <tt>zebraidx</tt> is run and you wish to address a given group
359 you specify that group with the <tt>-g</tt> option. In this case
360 settings that have the group name as their prefix will be used
361 by <tt>zebraidx</tt> and not default values. The default values have no prefix.
363 The group is written before the option itself, separated by a dot (.).
364 For instance, to set the record type for group <tt/public/ to <tt/grs/
365 (the common format for structured records)
369 public.recordType: grs
372 To set the default value of the record type to <tt/text/ write:
378 The configuration settings are summarized below. They will be
379 explained further in the following sections.
382 <tag><it>group</it>recordType<it>name</it></tag>
383 Specifies how records with the file extension <it>name</it> should
384 be handled by the indexer. This option may also be specified
385 as a command line option (<tt>-t</tt>). Note that if you do not
386 specify a <it/name/, the setting applies to all files.
387 <tag><it>group</it>recordId</tag>
388 Specifies how the record is to be identified when updated.
389 <tag><it>group</it>database</tag>
390 Specifies the Z39.50 database name.
391 <tag><it>group</it>storeKeys</tag>
392 Specifies whether key information should be saved for a given
393 group of records. If you plan to update/delete this type of
394 records later this should be specified as 1; otherwise it
395 should be 0 (default).
396 <tag><it>group</it>storeData</tag>
397 Specifies whether the records should be stored internally
398 in the Zebra system files. If you want to maintain the raw records yourself,
399 this option should be false (0). If you want Zebra to take care of the records
400 for you, it should be true(1).
402 Specifies the location of the various files that Zebra uses to represent
404 <tag>tempSetPath</tag>
405 Specifies the directory that the server uses for temporary result sets.
406 If not specified <tt>/tmp</tt> will be used.
407 <tag>profilePath</tag>
408 Specifies the location of profile specification paths.
410 Specifies the filename(s) of attribute set files for use in
411 searching. At least the Bib-1 set should be loaded (<tt/bib1.att/).
412 The <tt/profilePath/ setting is used to search for attribute set
416 <sect1>Locating Records
418 The default behaviour of the Zebra system is to reference the
419 records from their original location, i.e. where they were found when you
422 If your input files are temporary - for example if you retrieve
423 your records from an outside source, or if they where temporarily mounted on a CD-ROM,
424 you may want Zebra to make an internal copy of them. To do this,
425 you specify 1 (true) in the <tt>storedata</tt> setting. When
426 the Z39.50 server retrieves the records they will be read from the
427 internal file structures of the system.
429 <sect1>Indexing with no Record IDs (Simple Indexing)
432 If you have a set of records that you <em/never/ wish to delete
433 or modify you may find &dquot;indexing without records IDs&dquot; convenient.
434 This indexing method uses less space than the other methods and
437 To use this method, you simply don't provide the <tt>recordId</tt> entry
438 for the group of files that you index. To add a set of records you use
439 <tt>zebraidx</tt> with the <tt>update</tt> command. The
440 <tt>update</tt> command will always add all of the records to the index
441 because Zebra doesn't know how to match the new set of records with
444 Consider a system in which you have a group of text files called
445 <tt>simple</tt>. That group of records should belong to a Z39.50 database
446 called <tt>textbase</tt>. The following <tt/zebra.cfg/ file will suffice:
449 profilePath: /usr/local/yaz
451 simple.recordType: text
452 simple.database: textbase
455 Since the existing records in an index can not be addressed by their
456 IDs, it is impossible to delete or modify records when using this method.
458 <sect1>Indexing with File Record IDs
461 If you have a set of external records that you wish to index you may
462 use the file key feature of the Zebra system. In short, the file key
463 methodology uses the paths of the files containing records as their
464 unique identifiers. To perform indexing of a directory with file keys,
465 again, you specify the top-level directory after the <tt>update</tt>
466 command. The command will recursively traverse the directories and
467 compare each with whatever have been indexed before in the same
468 directory. If a file is new (not in the previous version of the
469 directory) it is inserted into the registers; if a file was already
470 indexed and it has been modified since the last insertionm, the index
471 is also modified; if a file has been removed since the last visit, it
472 is deleted from the index.
474 The resulting system is easy to administer. To delete a record
475 you simply have to delete the corresponding file (say, with the
477 To force update of a given file, you may use the <tt>touch</tt>
478 command. And to add files create new files (or directories with files).
479 For your changes to take effect in the register you must run <tt>zebraidx</tt> with
480 the same directory root again.
482 To use this method, you must specify <tt>file</tt> as the value
483 of <tt>recordId</tt> in the configuration file. In addition, you
484 should set <tt>storeKeys</tt> to <tt>1</tt>, since the Zebra
485 indexer must save additional information about the keys to each record in order to
486 modify the indices correctly at a later time.
488 For example, to update group <tt>esdd</tt> records below
489 <tt>/home/grs</tt> you could type:
491 $ zebraidx -g esdd update /home/grs
494 The corresponding configuration file includes:
501 <em>Important note: You cannot start out with a group of records with simple
502 indexing (no record IDs as in the previous section) and then later
503 enable file record Ids. Zebra must know from the first time that you
505 the files should be indexed with file record IDs.
508 You cannot explicitly delete records when using this method (using the
509 <bf/delete/ command to <tt/zebraidx/. Instead
510 you have to delete the files from the file system (or remove them)
511 and then run <tt>zebraidx</tt> with the <bf/update/ command again.
513 <sect1>Indexing with General Record IDs
515 When using this method you construct an (almost) arbritrary, internal
516 record key based on the contents of the record itself and other system
517 information. If you have a group of records that associates an ID with
518 each record, this method is convenient. For example, the record may
519 contain a title or a ID-number - unique within the group. In either
520 case you specify the Z39.50 attribute set and use-attribute location
521 in which this information is stored, and the system looks at this
522 field to determine the identity of the record.
524 As before, the record ID is defined by the <tt>recordId</tt> setting
525 in the configuration file. The value of the record ID specification
526 consists of one or more tokens separated by whitespace. The resulting
528 represented in the index by concatenating the tokens and separating them by
531 There are three kinds of tokens:
533 <tag>Internal record info</tag> The token refers to a key that is
534 extracted from the record. The syntax of this token is
535 <tt/(/ <em/set/ <tt/,/ <em/use/ <tt/)/, where <em/set/ is the
536 attribute set ordinal number and <em/use/ is the use value of the attribute.
537 <tag>System variable</tag> The system variables are preceded by
538 <verb>$</verb> and immediately followed by the system variable name, which
541 <tag>group</tag> Group name.
542 <tag>database</tag> Current database specified.
543 <tag>type</tag> Record type.
545 <tag>Constant string</tag> A string used as part of the ID — surrounded
546 by single- or double quotes.
549 The sample GILS records that come with the Zebra distribution contain a
551 in the Control-Identifier field. This field is mapped to the Bib-1
552 use attribute 1007. To use this field as a record id, specify
553 <tt>(1,1007)</tt> as the value of the <tt>recordId</tt> in the
554 configuration file. If you have other record types that uses
555 the same field for a different purpose, you might add the record type (or group or database name)
556 to the record id of the gils records as well, to prevent matches
557 with other types of records. In this case the recordId might be
560 gils.recordId: $type (1,1007)
563 As for the file record id case described in the previous section
564 updating your system is simply a matter of running <tt>zebraidx</tt>
565 with the <tt>update</tt> command. However, the update with general
566 keys is considerably slower than with file record IDs, since all files
567 visited must be (re)read to find their IDs.
569 You may have noticed that when using the general record IDs
570 method, you can only add or modify existing records with the <tt>update</tt>
571 command. If you wish to delete records, you must use the,
572 <tt>delete</tt> command, with a directory as a parameter.
573 This will remove all records that match the files below that root
576 <sect1>Register Location<label id="register-location">
579 Normally, the index files that form dictionaries, inverted
580 files, record info, etc., are stored in the directory where you run
581 <tt>zebraidx</tt>. If you wish to store these, possibly large, files
582 somewhere else, you must add the <tt>register</tt> entry to the
583 configuration file. Furthermore, the Zebra system allows its file
585 span multiple file systems, which is useful if a very large number of
588 The value <tt>register</tt> of register is a sequence of tokens.
589 Each token takes the form:
591 <em>dir</em><tt>:</tt><em>size</em>.
593 The <em>dir</em> specifies a directory in which index files will be
594 stored and the <em>size</em> specifies the maximum size of all
595 files in that directory. The Zebra indexer system fills each directory
596 in the order specified and use the next specified directories as needed.
597 The <em>size</em> is an integer followed by a qualifier
598 code, <tt>M</tt> for megabytes, <tt>k</tt> for kilobytes.
600 For instance, if you have two spare disks :) and the first disk is mounted
601 on <tt>/d1</tt> and has 200 Mb of free space and the
602 second, mounted on <tt>/d2</tt> has 300 Mb, you could
603 put this entry in your configuration file:
605 register: /d1:200M /d2:300M
608 Note that Zebra does not verify that the amount of space specified is
609 actually available on the directory (file system) specified - it is
610 your responsibility to ensure that enough space is available, and that
611 other applications do not use the free space. In a large production system,
612 it is recommended that you allocate one or more filesystem exclusively
613 to the Zebra register files.
615 <sect1>Safe Updating - Using Shadow Registers<label id="shadow-registers">
620 The Zebra server supports updating of the index structures. That is,
621 you can add records to databases managed by Zebra without rebuilding
622 the entire index. Since this process involves modifying structured
623 files with various references between blocks of data in the files, the
624 update process is inherently sensitive to system crashes, or to
625 process interruptions: Anything but a successfully completed update
626 process will leave the register files in an unknown state, and you
627 will essentially have no recourse but to re-index everything, or to
628 restore the register files from a backup medium. Further, while the
629 update process is active, users cannot be allowed to access the
630 system, as the contents of the register files may change unpredictably.
632 You can solve these problems by enabling the shadow register system in
633 Zebra. During the updating procedure, <tt/zebraidx/ will temporarily
634 write changes to the involved files in a set of &dquot;shadow
635 files&dquot;, without modifying the files that are accessed by the
636 active server processes. If the update procedure is interrupted by a
637 system crash or a signal, you simply repeat the procedure - the
638 register files have not been changed or damaged, and the partially
639 written shadow files are automatically deleted before the new updating
642 At the end of the updating procedure (or in a separate operation, if
643 you so desire), the system enters a &dquot;commit mode&dquot;. First,
644 any active server processes are forced to access those blocks that
645 have been changed from the shadow files rather than from the main
646 register files; the unmodified blocks are still accessed at their
647 normal location (the shadow files are not a complete copy of the
648 register files - they only contain those parts that have actually been
649 modified). If the process is interrupted at any point during the
650 commit process, the server processes will continue to access the
651 shadow files until you can repeat the commit procedure and complete
652 the writing of data to the main register files. You can perform
653 multiple update operations to the registers before you commit the
654 changes to the system files, or you can execute the commit operation
655 at the end of each update operation. When the commit phase has
656 completed successfully, any running server processes are instructed to
657 switch their operations to the new, operational register, and the
658 temporary shadow files are deleted.
660 <sect2>How to Use Shadow Register Files
663 The first step is to allocate space on your system for the shadow
664 files. You do this by adding a <tt/shadow/ entry to the <tt/zebra.cfg/
665 file. The syntax of the <tt/shadow/ entry is exactly the same as for
666 the <tt/register/ entry (see section <ref name="Register Location"
667 id="register-location">). The location of the shadow area should be
668 <it/different/ from the location of the main register area (if you
669 have specified one - remember that the default register area is the
670 working directory of the server and indexing processes).
672 The following excerpt from a <tt/zebra.cfg/ file shows one example of
673 a setup that configures both the main register location and the shadow
674 file area. Note that two directories or partitions have been set aside
675 for the shadow file area. You can specify any number of directories
676 for each of the file areas.
681 shadow: /scratch1:100M /scratch2:200M
684 When shadow files are enabled, an extra command is available at the
685 <tt/zebraidx/ command line. In order to make changes to the system
686 take effect for the users, you'll have to submit a
687 &dquot;commit&dquot; command after a (sequence of) update
688 operation(s). You can ask the indexer to commit the changes
689 immediately after the update operation:
692 $ zebraidx update /d1/records update /d2/more-records commit
695 Or you can execute multiple updates before committing the changes:
698 $ zebraidx -g books update /d1/records update /d2/more-records
699 $ zebraidx -g fun update /d3/fun-records
703 If one of the update operations above had been interrupted, the commit
704 operation on the last line would fail: <tt/zebraidx/ will not let you
705 commit changes that would destroy the running register. You'll have to
706 rerun all of the update operations since your last commit operation,
707 before you can commit the new changes.
709 Similarly, if the commit operation fails, <tt/zebraidx/ will not let
710 you start a new update operation before you have successfully repeated
711 the commit operation. The server processes will keep accessing the
712 shadow files rather than the (possibly damaged) blocks of the main
713 register files until the commit operation has successfully completed.
715 You should be aware that update operations may take slightly longer
716 when the shadow register system is enabled, since more file access
717 operations are involved. Further, while the disk space required for
718 the shadow register data is modest for a small update operation, you
719 may prefer to disable the system if you are adding a very large number
720 of records to an already very large database (we use the terms
721 <it/large/ and <it/modest/ very loosely here, since every
722 application's perception of size is different). To update the system
723 without the use of the the shadow files, simply run <tt/zebraidx/ with
724 the <tt/-n/ option (note that you do not have to execute the
725 <bf/commit/ command of <tt/zebraidx/ when you temporarily disable the
726 use of the shadow registers in this fashion. Note also that, just as
727 when the shadow registers are not enabled, server processes will be
728 barred from accessing the main register while the update procedure
731 <sect>Running the Maintenance Interface (zebraidx)
734 The following is a complete reference to the command line interface to
735 the <tt/zebraidx/ application.
739 $ zebraidx [options] command [directory] ...
743 <tag>-t <it/type/</tag>Update all files as <it/type/. Currently, the
744 types supported are <tt/text/ and <tt/grs/<it/.filter/. If no
745 <it/filter/ is provided for the GRS (General Record Structure) type,
746 the canonical input format is assumed (see section <ref
747 id="local-representation" name="Local Representation">). Generally, it
748 is probably advisable to specify the record types in the
749 <tt/zebra.cfg/ file (see section <ref id="record-types" name="Record Types">).
751 <tag>-c <it/config-file/</tag>Read the configuration file
752 <it/config-file/ instead of <tt/zebra.cfg/.
754 <tag>-g <it/group/</tag>Update the files according to the group
755 settings for <it/group/ (see section <ref id="configuration-file"
756 name="The Zebra Configuration File">).
758 <tag>-d <it/database/</tag>The records located should be associated
759 with the database name <it/database/ for access through the Z39.50
762 <tag>-d <it/mbytes/</tag>Use <it/mbytes/ of megabytes before flushing
763 keys to background storage. This setting affects performance when
764 updating large databases.
766 <tag>-n</tag>Disable the use of shadow registers for this operation
767 (see section <ref id="shadow-registers" name="Robust Updating - Using
770 <tag>-v <it/level/</tag>Set the log level to <it/level/. <it/level/
771 should be one of <tt/none/, <tt/debug/, and <tt/all/.
777 <tag>Update <it/directory/</tag>Update the register with the files
778 contained in <it/directory/. If no directory is provided, a list of
779 files is read from <tt/stdin/. See section <ref
780 id="administrating" name="Administrating Zebra">.
782 <tag>Delete <it/directory/</tag>Remove the records corresponding to
783 the files found under <it/directory/ from the register.
785 <tag/Commit/Write the changes resulting from the last <bf/update/
786 commands to the register. This command is only available if the use of
787 shadow register files is enabled (see section <ref
788 id="shadow-registers" name="Robust Updating - Using Shadow
793 <sect>Running the Z39.50 Server (zebrasrv)
798 zebrasrv [options] [listener-address ...]
802 <tag>-a <it/APDU file/</tag> Specify a file for dumping PDUs (for diagnostic purposes).
803 The special name &dquot;-&dquot; sends output to <tt/stderr/.
805 <tag>-c <it/config-file/</tag> Read configuration information from <it/config-file/. The default configuration is <tt/./zebra.cfg/.
807 <tag/-S/Don't fork on connection requests. This can be useful for
808 symbolic-level debugging. The server can only accept a single
809 connection in this mode.
811 <tag/-s/Use the SR protocol.
813 <tag/-z/Use the Z39.50 protocol (default). These two options complement
814 eachother. You can use both multiple times on the same command
815 line, between listener-specifications (see below). This way, you
816 can set up the server to listen for connections in both protocols
817 concurrently, on different local ports.
819 <tag>-l <it/logfile/</tag>Specify an output file for the diagnostic
820 messages. The default is to write this information to <tt/stderr/.
822 <tag>-v <it/log-level/</tag>The log level. Use a comma-separated list of members of the set
823 {fatal,debug,warn,log,all,none}.
825 <tag>-u <it/username/</tag>Set user ID. Sets the real UID of the server process to that of the
826 given <it/username/. It's useful if you aren't comfortable with having the
827 server run as root, but you need to start it as such to bind a
831 A <it/listener-address/ consists of a transport mode followed by a
832 colon (:) followed by a listener address. The transport mode is
833 either <tt/osi/ or <tt/tcp/.
835 For TCP, an address has the form
838 hostname | IP-number [: portnumber]
841 The port number defaults to 210 (standard Z39.50 port).
843 For OSI (only available if the server is compiled with XTI/mOSI
844 support enabled), the address form is
847 [t-selector /] hostname | IP-number [: portnumber]
850 The transport selector is given as a string of hex digits (with an even
851 number of digits). The default port number is 102 (RFC1006 port).
859 osi:0402/dbserver.osiworld.com:3000
863 In both cases, the special hostname &dquot;@&dquot; is mapped to
864 the address INADDR_ANY, which causes the server to listen on any local
865 interface. To start the server listening on the registered ports for
866 Z39.50 and SR over OSI/RFC1006, and to drop root privileges once the
867 ports are bound, execute the server like this (from a root shell):
870 zebrasrv -u daemon tcp:@ -s osi:@
873 You can replace <tt/daemon/ with another user, eg. your own account, or
874 a dedicated IR server account.
876 The default behavior for <tt/zebrasrv/ is to establish a single TCP/IP
877 listener, for the Z39.50 protocol, on port 9999.
879 <sect>The Record Model
882 The Zebra system is designed to span a wide range of data management
883 applications. The system can be configured to handle virtually any
884 kind of structured data. Each record in the system is associated with
885 a <it/record schema/ which lends context to the data elements of the
886 record. Any number of record schema can coexist in the system.
887 Although it may be wise to use only a single schema within
888 one database, the system poses no such restrictions.
890 Records pass through three different states during processing in the
894 <item>When records are first entered into the system, they are represented
895 in their local, or native format. This might be SGML or HTML files,
896 News or Mail archives, MARC records. If the system doesn't already
897 know how to read the type of data you need to store, you can set up an
898 input filter by preparing conversion rules based on regular
899 expressions and a flexible scripting language (Tcl). The input filter
900 produces as output an internal representation:
902 <item>When records are processed by the system, they are represented
903 in a tree-structure, constructed by tagged data elements hanging off a
904 root node. The tagged elements may contain data or yet more tagged
905 elements in a recursive structure. The system performs various
906 actions on this tree structure (indexing, element selection, schema
909 <item>Before transmitting records to the client, they are first
910 converted from the internal structure to a form suitable for exchange
911 over the network - according to the Z39.50 standard.
914 <sect1>Local Representation<label id="local-representation">
917 As mentioned earlier, Zebra places few restrictions on the type of
918 data that you can index and manage. Generally, whatever the form of
919 the data, it is parsed by an input filter specific to that format, and
920 turned into an internal structure that Zebra knows how to handle. This
921 process takes place whenever the record is accessed - for indexing and
924 <sect2>Canonical Input Format
927 Although input data can take any form, it is sometimes useful to
928 describe the record processing capabilities of the system in terms of
929 a single, canonical input format that gives access to the full
930 spectrum of structure and flexibility in the system. In Zebra, this
931 canonical format is an &dquot;SGML-like&dquot; syntax.
933 Consider a record describing an information resource (such a record is
934 sometimes known as a <it/locator record/). It might contain a field
935 describing the distributor of the information resource, which might in
936 turn be partitioned into various fields providing details about the
937 distributor, like this:
941 <Name> USGS/WRD &etago;Name>
942 <Organization> USGS/WRD &etago;Organization>
944 U.S. GEOLOGICAL SURVEY, 505 MARQUETTE, NW
945 &etago;Street-Address>
946 <City> ALBUQUERQUE &etago;City>
947 <State> NM &etago;State>
948 <Zip-Code> 87102 &etago;Zip-Code>
949 <Country> USA &etago;Country>
950 <Telephone> (505) 766-5560 &etago;Telephone>
954 <it>NOTE: The indentation used above is used to illustrate how Zebra
955 interprets the expression. The indentation, in itself, has no
956 significance to the parser for the canonical input format, which
957 ignores all whitespace.</it>
959 The keywords surrounded by <...> are <it/tags/, while the
960 sections of text in between are the <it/data elements/. A data element
961 is characterized by its location in the tree that is made up by the
962 nested elements. Each element is terminated by a closing tag -
963 beginning with &etago;, and containing the same symbolic tag-name as
964 the corresponding opening tag. The general closing tag - &etago;> -
965 terminates the element started by the last opening tag. The
966 structuring of elements is significant. The element <bf/Telephone/,
967 for instance, may be indexed and presented to the client differently,
968 depending on whether it appears inside the <bf/Distributor/ element,
969 or some other data element.
974 The first tag in a record describes the root node of the tree that
975 makes up the total record. In the canonical input format, the root tag
976 should contain the name of the schema that lends context to the
977 elements of the record (see section <ref id="internal-representation"
978 name="Internal Representation">). The following is a GILS record that
979 contains only a single element (strictly speaking, that makes it an
980 illegal GILS record, since the GILS profile includes several mandatory
981 elements - Zebra does not validate the contents of a record against
982 the Z39.50 profile, however):
986 <title>Zen and the Art of Motorcycle Maintenance&etago;title>
993 Zebra allows you to provide individual data elements in a number of
994 <it/variant forms/. Examples of variant forms are textual data
995 elements which might appear in different languages, and images which
996 may appear in different formats or layouts. The variant system is
997 essentially a clean representation of the variant mechanism of
1000 The following is an example of a title element which occurs in two
1001 different languages.
1005 <var lang lang "eng">
1006 Zen and the Art of Motorcycle Maintenance&etago;>
1007 <var lang lang "dan">
1008 Zen og Kunsten at Vedligeholde en Motorcykel&etago;>
1012 The syntax of the <it/variant element/ is <tt><<bf/var/ <it/class
1013 type value/></tt>. The available values for the <it/class/ and
1014 <it/type/ fields are given by the variant set that is associated with the
1015 current schema (see section <ref id="variant-set" name="Variant Set
1018 Variant elements are terminated by the general end-tag &etago;>, by
1019 the variant end-tag &etago;var>, by the appearance of another variant
1020 tag with the same <it/class/ and <it/value/ settings, or by the
1021 appearance of another, normal tag. In other words, the end-tags for
1022 the variants used in the example above could have been saved.
1024 Variant elements can be nested. The element
1028 <var lang lang "eng"><var body iana "text/plain">
1029 Zen and the Art of Motorcycle Maintenance
1033 Associates two variant components to the variant list for the title
1034 element. Given the nesting rules described above, we could write
1038 <var body iana "text/plain>
1039 <var lang lang "eng">
1040 Zen and the Art of Motorcycle Maintenance
1041 <var lang lang "dan">
1042 Zen og Kunsten at Vedligeholde en Motorcykel
1046 The title element above comes in two variants. Both have the IANA body
1047 type &dquot;text/plain&dquot;, but one is in English, and the other in
1050 <sect2>Input Filters
1053 In order to handle general, text-based input formats, Zebra allows the
1054 operator to specify filters which read individual records in their native format
1055 and produce an internal representation that the system can
1058 Input filters are ASCII files, generally with the suffix <tt/.flt/.
1059 The system looks for the files in the directories given in the
1060 <bf/profilePath/ setting in the <tt/zebra.cfg/ file.
1062 Generally, an input filter consists of a sequence of rules, where each
1063 rule consists of a sequence of expressions, followed by an action. The
1064 expressions are evaluated against the contents of the input record,
1065 and the actions normally contribute to the generation of an internal
1066 representation of the record.
1068 An expression can be either of the following:
1071 <tag/INIT/The action associated with this expression is evaluated
1072 exactly once in the lifetime of the application, before any records
1073 are read. It can be used in conjunction with an action that
1074 initializes tables or other resources that are used in the processing
1077 <tag/BEGIN/Matches the beginning of the record. It can be used to
1078 initialize variables, etc. Typically, the <bf/BEGIN/ rule is also used
1079 to establish the root node of the record.
1081 <tag/END/Matches the end of the record - when all of the contents
1082 of the record has been processed.
1084 <tag>/pattern/</tag>Matches a string of characters from the input
1087 <tag/BODY/This keyword may only be used between two patterns. It
1088 matches everything between (not including) those patterns.
1090 <tag/FINISH/THe expression asssociated with this pattern is evaluated
1091 once, before the application terminates. It can be used to release
1092 system resources - typically ones allocated in the <bf/INIT/ step.
1096 An action is surrounded by curly braces ({...}), and consists of a
1097 sequence of statements. Statements may be separated by newlines or
1098 semicolons (;). Within actions, the strings that matched the
1099 expressions immediately preceding the action can be referred to as
1100 $0, $1, $2, etc.
1102 The available statements are:
1106 <tag>begin <it/type [parameter ... ]/</tag>Begin a new
1107 data element. The type is one of the following:
1109 <tag/record/Begin a new record. The parameter should be the
1110 name of the schema that describes the structure of the record, eg.
1111 <tt/gils/ or <tt/wais/. The <tt/begin record/ call should come before
1112 any other call to <bf/begin/.
1114 <tag/element/Begin a new tagged element. The parameter is the
1115 name of the tag. If the tag is not matched anywhere in the tagsets
1116 referenced by the current schema, it is treated as a local string
1119 <tag/variant/Begin a new node in a variant tree. The parameters are
1120 <it/class type value/.
1124 <tag/data/Create a data element under. The concatenated arguments make
1125 up the value of the data element. The option <tt/-text/ signals that
1126 the layout (whitespace) of the data should be retained for
1127 transmission. The option <tt/-element/ <it/tag/ wraps the data up in
1128 the <it/tag/. The use of the <tt/-element/ option is equivalent to
1129 preceding the command with a <bf/begin element/ command, and following
1130 it with the <bf/end/ command.
1132 <tag>end <it/[type]/</tag>Close a data element. If no parameter is given,
1133 the last element on the stack is terminated. The first parameter, if
1134 any, is a type name, similar to the <bf/begin/ statement. For the
1135 <bf/element/ type, a tag name can be provided to terminate a specific tag.
1139 The following input filter reads a Usenet news file, producing a
1140 record in the WAIS schema.
1143 BEGIN { begin record wais }
1145 /^From:/ BODY /$/ { data -element name $1 }
1146 /^Subject:/ BODY /$/ { data -element title $1 }
1147 /^Date:/ BODY /$/ { data -element lastModified $1 }
1149 begin element bodyOfDisplay
1150 begin variant body iana "text/plain"
1156 If Zebra is compiled with support for Tcl (Tool Command Language)
1157 enabled, the statements described above are supplemented with a complete
1158 scripting environment, including control structures (conditional
1159 expressions and loop constructs), and powerful string manipulation
1160 mechanisms for modifying the elements of a record. Tcl is a popular
1161 scripting environment, with several tutorials available both online
1164 <it>NOTE: Tcl support is not currently available, but will be
1165 included with the next release.</it>
1167 <sect1>Internal Representation<label id="internal-representation">
1170 When records are manipulated by the system, they're represented in a
1171 tree-structure, with data elements at the leaf nodes, and tags or
1172 variant components at the non-leaf nodes. The root-node identifies the
1173 schema that lends context to the tagging and structuring of the
1174 record. Imagine a simple record, consisting of a 'title' element and
1175 an 'author' element:
1178 TITLE "Zen and the Art of Motorcycle Maintenance"
1180 AUTHOR "Robert Pirsig"
1183 A slightly more complex record would have the author element consist
1184 of two elements, a surname and a first name:
1187 TITLE "Zen and the Art of Motorcycle Maintenance"
1194 The root of the record will refer to the record schema that describes
1195 the structuring of this particular record. The schema defines the
1196 element tags (TITLE, FIRST-NAME, etc.) that occur in the record, as
1197 well as the structuring (SURNAME should appear below AUTHOR, etc.). In
1198 addition, the schema establishes element set names that are used by
1199 the client to request a subset of the elements of a given record. The
1200 schema may also establish rules for converting the record to a
1201 different schema, by stating, for each element, a mapping to a
1204 The following sections describe the configuration files that govern
1205 the internal management of records. The system searches for the files
1206 in the directories specified by the <bf/profilePath/ setting in the
1207 <tt/zebra.cfg/ file.
1209 <sect2>The Abstract Syntax
1212 The abstract syntax definition (ARS) is the focal point of the
1213 record schema description. For a given schema, it may state any
1214 or all of the following:
1217 <item>The object identifier of the Z39.50 schema associated
1218 with the ARS, so that it can be referred to by the client.
1220 <item>The attribute set (which can possibly be a compound of multiple
1221 sets) which applies in the profile. This is used when indexing and
1222 searching the records belonging to the given profile.
1224 <item>The Tag set (again, this can consist of several different sets).
1225 This is used when reading the records from a file, to recognize the
1226 different tags, and when transmitting the record to the client -
1227 mapping the tags to their numerical representation, if they are
1230 <item>The variant set which is used in the profile. This provides a
1231 vocabulary for specifying the <it/forms/ of data that appear inside
1234 <item>Element set names, which are a shorthand way for the client to
1235 ask for a subset of the data elements contained in a record. Element
1236 set names, in the retrieval module, are mapped to <it/element
1237 specifications/, which contain information equivalent to the
1238 <it/Espec-1/ syntax of Z39.50.
1240 <item>Map tables, which may specify mappings to <it/other/ database
1241 profiles, if desired.
1243 <item>Possibly, a set of rules describing the mapping of elements to a
1244 MARC representation.
1246 <item>A list of element descriptions (this is the actual ARS of the
1247 schema, in Z39.50 terms), which lists the ways in which the various
1248 tags can be used and organized hierarchically.
1251 Several of the entries above simply refer to other files, which
1252 describe the given objects.
1254 <sect2>The Configuration Files
1257 This section describes the syntax and use of the various tables which
1258 are used by the retrieval module.
1260 The number of different file types may appear daunting at first, but
1261 each type corresponds fairly clearly to a single aspect of the Z39.50
1262 retrieval facilities. Further, the average database administrator
1263 who is simply reusing an existing profile for which tables already
1264 exist, shouldn't have to worry too much about the contents of these tables.
1266 Generally, the files are simple ASCII files, which can be maintained
1267 using any text editor. Blank lines, and lines beginning with a (#) are
1268 ignored. Any characters followed by a (#) are also ignored. All other
1269 lines contain <it/directives/, which establish some setting or value
1270 to the system. Generally, settings are characterized by a single
1271 keyword, identifying the setting, followed by a number of parameters.
1272 Some settings are repeatable (r), while others may occur only once in a
1273 file. Some settings are optional (o), whicle others again are
1276 <sect2>The Abstract Syntax (.abs) Files
1279 The name of this file type is slightly misleading in Z39.50 terms,
1280 since, apart from the actual abstract syntax of the profile, it also
1281 includes most of the other definitions that go into a database
1284 When a record in the canonical, SGML-like format is read from a file
1285 or from the database, the first tag of the file should reference the
1286 profile that governs the layout of the record. If the first tag of the
1287 record is, say, <tt><gils></tt>, the system will look for the profile
1288 definition in the file <tt/gils.abs/. Profile definitions are cached,
1289 so they only have to be read once during the lifespan of the current
1292 When writing your own input filters, the <bf/record-begin/ command
1293 introduces the profile, and should always be called first thing when
1294 introducing a new record.
1296 The file may contain the following directives:
1299 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1300 description for the profile. Mostly useful for diagnostic purposes.
1302 <tag>reference <it/OID-name/</tag> (m) The reference name of the OID for
1303 the profile. The reference names can be found in the <bf/util/
1306 <tag>attset <it/filename/</tag> (m) The attribute set that is used for
1307 indexing and searching records belonging to this profile.
1309 <tag>tagset <it/filename/</tag> (o) The tag set (if any) that describe
1310 that fields of the records.
1312 <tag>varset <it/filename/</tag> (o) The variant set used in the profile.
1314 <tag>maptab <it/filename/</tag> (o,r) This points to a
1315 conversion table that might be used if the client asks for the record
1316 in a different schema from the native one.
1318 <tag>marc <it/filename/</tag> (o) Points to a file containing parameters
1319 for representing the record contents in the ISO2709 syntax. Read the
1320 description of the MARC representation facility below.
1322 <tag>esetname <it/name filename/</tag> (o,r) Associates the
1323 given element set name with an element selection file. If an (@) is
1324 given in place of the filename, this corresponds to a null mapping for
1325 the given element set name.
1327 <tag>elm <it/path name attribute/</tag> (o,r) Adds an element
1328 to the abstract record syntax of the schema. The <it/path/ follows the
1329 syntax which is suggested by the Z39.50 document - that is, a sequence
1330 of tags separated by slashes (/). Each tag is given as a
1331 comma-separated pair of tag type and -value surrounded by parenthesis.
1332 The <it/name/ is the name of the element, and the <it/attribute/
1333 specifies what attribute to use when indexing the element. A ! in
1334 place of the attribute name is equivalent to specifying an attribute
1335 name identical to the element name. A - in place of the attribute name
1336 specifies that no indexing is to take place for the given element.
1340 NOTE: The mechanism for controlling indexing is not adequate for
1341 complex databases, and will probably be moved into a separate
1342 configuration table eventually.
1345 The following is an excerpt from the abstract syntax file for the GILS
1350 reference GILS-schema
1355 maptab gils-usmarc.map
1359 esetname VARIANT gils-variant.est # for WAIS-compliance
1360 esetname B gils-b.est
1361 esetname G gils-g.est
1366 elm (1,14) localControlNumber Local-number
1367 elm (1,16) dateOfLastModification Date/time-last-modified
1369 elm (4,1) controlIdentifier Identifier-standard
1370 elm (2,6) abstract Abstract
1371 elm (4,51) purpose !
1372 elm (4,52) originator -
1373 elm (4,53) accessConstraints !
1374 elm (4,54) useConstraints !
1375 elm (4,70) availability -
1376 elm (4,70)/(4,90) distributor -
1377 elm (4,70)/(4,90)/(2,7) distributorName !
1378 elm (4,70)/(4,90)/(2,10 distributorOrganization !
1379 elm (4,70)/(4,90)/(4,2) distributorStreetAddress !
1380 elm (4,70)/(4,90)/(4,3) distributorCity !
1383 <sect2>The Attribute Set (.att) Files
1386 This file type describes the <bf/Use/ elements of an attribute set.
1387 It contains the following directives.
1391 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1392 description for the attribute set. Mostly useful for diagnostic purposes.
1394 <tag>reference <it/OID-name/</tag> (m) The reference name of the OID for
1395 the attribute set. The reference names can be found in the <bf/util/
1398 <tag>ordinal <it/integer/</tag> (m) This value will be used to represent the
1399 attribute set in the index. Care should be taken that each attribute
1400 set has a unique ordinal value.
1402 <tag>include <it/filename/</tag> (o,r) This directive is used to
1403 include another attribute set as a part of the current one. This is
1404 used when a new attribute set is defined as an extension to another
1405 set. For instance, many new attribute sets are defined as extensions
1406 to the <bf/bib-1/ set. This is an important feature of the retrieval
1407 system of Z39.50, as it ensures the highest possible level of
1408 interoperability, as those access points of your database which are
1409 derived from the external set (say, bib-1) can be used even by clients
1410 who are unaware of the new set.
1412 <tag>att <it/att-value att-name [local-value]/</tag> (o,r) This
1413 repeatable directive introduces a new attribute to the set. The
1414 attribute value is stored in the index (unless a <it/local-value/ is
1415 given, in which case this is stored). The name is used to refer to the
1416 attribute from the <it/abstract syntax/. </descrip>
1418 This is an excerpt from the GILS attribute set definition. Notice how
1419 the file describing the <it/bib-1/ attribute set is referenced.
1423 reference GILS-attset
1427 att 2001 distributorName
1428 att 2002 indexTermsControlled
1430 att 2004 accessConstraints
1431 att 2005 useConstraints
1434 <sect2>The Tag Set (.tag) Files
1437 This file type defines the tagset of the profile, possibly by
1438 referencing other tag sets (most tag sets, for instance, will include
1439 tagsetG and tagsetM from the Z39.50 specification. The file may
1440 contain the following directives.
1443 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1444 description for the tag set. Mostly useful for diagnostic purposes.
1446 <tag>reference <it/OID-name/</tag> (o) The reference name of the OID for
1447 the tag set. The reference names can be found in the <bf/util/
1448 module of <bf/YAZ/. The directive is optional, since not all tag sets
1449 are registered outside of their schema.
1451 <tag>type <it/integer/</tag> (m) The type number of the tag within the schema
1454 <tag>include <it/filename/</tag> (o,r) This directive is used
1455 to include the definitions of other tag sets into the current one.
1457 <tag>tag <it/number names type/</tag> (o,r) Introduces a new
1458 tag to the set. The <it/number/ is the tag number as used in the protocol
1459 (there is currently no mechanism for specifying string tags at this
1460 point, but this would be quick work to add). The <it/names/ parameter
1461 is a list of names by which the tag should be recognized in the input
1462 file format. The names should be separated by slashes (/). The
1463 <it/type/ is th recommended datatype of the tag. It should be one of
1471 <item>generalizedtime
1479 The following is an excerpt from the TagsetG definition file.
1488 tag 3 publicationPlace string
1489 tag 4 publicationDate string
1490 tag 5 documentId string
1491 tag 6 abstract string
1493 tag 8 date generalizedtime
1494 tag 9 bodyOfDisplay string
1495 tag 10 organization string
1498 <sect2>The Variant Set (.var) Files<label id="variant-set">
1501 The variant set file is a straightforward representation of the
1502 variant set definitions associated with the protocol. At present, only
1503 the <it/Variant-1/ set is known.
1505 These are the directives allowed in the file.
1508 <tag>name <it/symbolic-name/</tag> (m) This provides a shorthand name or
1509 description for the variant set. Mostly useful for diagnostic purposes.
1511 <tag>reference <it/OID-name/</tag> (o) The reference name of the OID for
1512 the variant set, if one is required. The reference names can be found
1513 in the <bf/util/ module of <bf/YAZ/.
1515 <tag>class <it/integer class-name/</tag> (m,r) Introduces a new
1516 class to the variant set.
1518 <tag>type <it/integer type-name datatype/</tag> (m,r) Addes a
1519 new type to the current class (the one introduced by the most recent
1520 <bf/class/ directive). The type names belong to the same name space as
1521 the one used in the tag set definition file.
1524 The following is an excerpt from the file describing the variant set
1533 type 1 variantId octetstring
1538 type 2 z39.50 string
1542 <sect2>The Element Set (.est) Files
1545 The element set specification files describe a selection of a subset
1546 of the elements of a database record. The element selection mechanism
1547 is equivalent to the one supplied by the <it/Espec-1/ syntax of the
1548 Z39.50 specification. In fact, the internal representation of an
1549 element set specification is identical to the <it/Espec-1/ structure,
1550 and we'll refer you to the description of that structure for most of
1551 the detailed semantics of the directives below.
1554 NOTE: Not all of the Espec-1 functionality has been implemented yet.
1555 The fields that are mentioned below all work as expected, unless
1559 The directives available in the element set file are as follows:
1562 <tag>defaultVariantSetId <it/OID-name/</tag> (o) If variants are used in
1563 the following, this should provide the name of the variantset used
1564 (it's not currently possible to specify a different set in the
1565 individual variant request). In almost all cases (certainly all
1566 profiles known to us), the name <tt/Variant-1/ should be given here.
1568 <tag>defaultVariantRequest <it/variant-request/</tag> (o) This directive
1569 provides a default variant request for
1570 use when the individual element requests (see below) do not contain a
1571 variant request. Variant requests consist of a blank-separated list of
1572 variant components. A variant compont is a comma-separated,
1573 parenthesized triple of variant class, type, and value (the two former
1574 values being represented as integers). The value can currently only be
1575 entered as a string (this will change to depend on the definition of
1576 the variant in question). The special value (@) is interpreted as a
1577 null value, however.
1579 <tag>simpleElement <it/path ['variant' variant-request]/</tag>
1580 (o,r) This corresponds to a simple element request in <it/Espec-1/. The
1581 path consists of a sequence of tag-selectors, where each of these can
1585 <item>A simple tag, consisting of a comma-separated type-value pair in
1586 parenthesis, possibly followed by a colon (:) followed by an
1587 occurrences-specification (see below). The tag-value can be a number
1588 or a string. If the first character is an apostrophe ('), this forces
1589 the value to be interpreted as a string, even if it appears to be numerical.
1591 <item>A WildThing, represented as a question mark (?), possibly
1592 followed by a colon (:) followed by an occurrences specification (see
1595 <item>A WildPath, represented as an asterisk (*). Note that the last
1596 element of the path should not be a wildPath (wildpaths don't work in
1600 The occurrences-specification can be either the string <tt/all/, the
1601 string <tt/last/, or an explicit value-range. The value-range is
1602 represented as an integer (the starting point), possibly followed by a
1603 plus (+) and a second integer (the number of elements, default being
1606 The variant-request has the same syntax as the defaultVariantRequest
1607 above. Note that it may sometimes be useful to give an empty variant
1608 request, simply to disable the default for a specific set of fields
1609 (we aren't certain if this is proper <it/Espec-1/, but it works in
1610 this implementation).
1613 The following is an example of an element specification belonging to
1617 simpleelement (1,10)
1618 simpleelement (1,12)
1620 simpleelement (1,14)
1622 simpleelement (4,52)
1625 <sect2>The Schema Mapping (.map) Files<label id="schema-mapping">
1628 Sometimes, the client might want to receive a database record in
1629 a schema that differs from the native schema of the record. For
1630 instance, a client might only know how to process WAIS records, while
1631 the database record is represented in a more specific schema, such as
1632 GILS. In this module, a mapping of data to one of the MARC formats is
1633 also thought of as a schema mapping (mapping the elements of the
1634 record into fields consistent with the given MARC specification, prior
1635 to actually converting the data to the ISO2709). This use of the
1636 object identifier for USMARC as a schema identifier represents an
1637 overloading of the OID which might not be entirely proper. However,
1638 it represents the dual role of schema and record syntax which
1639 is assumed by the MARC family in Z39.50.
1642 NOTE: The schema-mapping functions are so far limited to a
1643 straightforward mapping of elements. This should be extended with
1644 mechanisms for conversions of the element contents, and conditional
1645 mappings of elements based on the record contents.
1648 These are the directives of the schema mapping file format:
1651 <tag>targetName <it/name/</tag> (m) A symbolic name for the target schema
1652 of the table. Useful mostly for diagnostic purposes.
1654 <tag>targetRef <it/OID-name/</tag> (m) An OID name for the target schema.
1655 This is used, for instance, by a server receiving a request to present
1656 a record in a different schema from the native one. The name, again,
1657 is found in the <bf/oid/ module of <bf/YAZ/.
1659 <tag>map <it/element-name target-path/</tag> (o,r) Adds
1660 an element mapping rule to the table.
1663 <sect2>The MARC (ISO2709) Representation (.mar) Files
1666 This file provides rules for representing a record in the ISO2709
1667 format. The rules pertain mostly to the values of the constant-length
1668 header of the record.
1670 <it>NOTE: This will be described better. We're in the process of
1671 re-evaluating and most likely changing the way that MARC records are
1672 handled by the system.</it>
1674 <sect1>Exchange Formats
1677 Converting records from the internal structure to en exchange format
1678 is largely an automatic process. Currently, the following exchange
1679 formats are supported:
1682 <item>GRS-1. The internal representation is based on GRS-1, so the
1683 conversion here is straightforward. The system will create
1684 applied variant and supported variant lists as required, if a record
1685 contains variant information.
1687 <item>SUTRS. Again, the mapping is fairly straighforward. Indentation
1688 is used to show the hierarchical structure of the record.
1690 <item>ISO2709-based formats (USMARC, etc.). Only records with a
1691 two-level structure (corresponding to fields and subfields) can be
1692 directly mapped to ISO2709. For records with a different structuring
1693 (eg., GILS), the representation in a structure like USMARC involves a
1694 schema-mapping (see section <ref id="schema-mapping" name="Schema
1695 Mapping">), to an &dquot;implied&dquot; USMARC schema (implied,
1696 because there is no formal schema which specifies the use of the
1697 USMARC fields outside of ISO2709). The resultant, two-level record is
1698 then mapped directly from the internal representation to ISO2709. See
1699 the GILS schema definition files for a detailed example of this
1702 <item>Explain. This representation is only available for records
1703 belonging to the Explain schema.
1710 Copyright © 1995, Index Data.
1712 All rights reserved.
1714 Use and redistribution in source or binary form, with or without
1715 modification, of any or all of this software and documentation is
1716 permitted, provided that the following conditions are met:
1718 1. This copyright and permission notice appear with all copies of the
1719 software and its documentation. Notices of copyright or attribution
1720 which appear at the beginning of any file must remain unchanged.
1722 2. The names of Index Data or the individual authors may not be used to
1723 endorse or promote products derived from this software without specific
1724 prior written permission.
1726 3. Source code or binary versions of this software and its
1727 documentation may be used freely in not-for-profit applications. For
1728 profit applications - such as providing for-pay database services,
1729 marketing a product based in whole or in part on this software or its
1730 documentation, or generally distributing this software or its
1731 documentation under a different license - requires a commercial
1732 license from Index Data. The software may be installed and used for
1733 evaluation purposes in conjunction with a commercial application for a
1734 trial period of no more than 60 days.
1736 THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
1737 EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
1738 WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
1739 IN NO EVENT SHALL INDEX DATA BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
1740 INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES
1741 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR
1742 NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
1743 LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
1746 <sect>About Index Data and the Zebra Server
1749 Index Data is a consulting and software-development enterprise that
1750 specialises in library and information management systems. Our
1751 interests and expertise span a broad range of related fields, and one
1752 of our primary, long-term objectives is the development of a powerful
1753 information management
1754 system with open network interfaces and hypermedia capabilities.
1756 We make this software available free of charge for not-for-profit
1757 purposes, as a service to the networking community, and to further
1758 the development and use of quality software for open network
1761 If you like this software, and would like to use all or part of it in
1762 a commercial product, or to provide a commercial database service,
1763 please contact us to discuss the details. We'll be happy to answer
1764 questions about the software, and about our services in general. If
1765 you have specific requirements to the software, we'll be glad to offer
1766 our advice - and if you need to adapt the software to a special
1767 purpose, our consulting services and expert knowledge of the software
1768 is available to you at favorable rates.
1773 DK-2200 København N&nl
1778 Phone: +45 3536 3672
1780 Email: info@index.ping.dk
1783 The <it>Random House College Dictionary</it>, 1975 edition
1784 offers this definition of the
1785 word &dquot;Zebra&dquot;:
1788 Zebra, n., any of several horselike, African mammals of the genus Equus,
1789 having a characteristic pattern of black or dark-brown stripes on
1790 a whitish background.