X-Git-Url: http://git.indexdata.com/?p=idzebra-moved-to-github.git;a=blobdiff_plain;f=doc%2Fintroduction.xml;h=68fcc928028c6450da7ca0c973cb0fabda8bee07;hp=0f39ec994c376445b1fc9eb8c4648bf0145a672c;hb=7c3a0352f0492609a3b6b26b63a72b0b2d207aab;hpb=dd8372e3f27c68a0410f13044dd184ccde8ca243 diff --git a/doc/introduction.xml b/doc/introduction.xml index 0f39ec9..68fcc92 100644 --- a/doc/introduction.xml +++ b/doc/introduction.xml @@ -1,116 +1,120 @@ + Introduction Overview - The Zebra system is a fielded free-text indexing and retrieval engine with a - Z39.50 frontend. You can use any commercial or freeware Z39.50 client - to access data stored in Zebra. + Zebra + is a high-performance, general-purpose structured text + indexing and retrieval engine. It reads records in a + variety of input formats (eg. email, XML, MARC) and provides access + to them through a powerful combination of boolean search + expressions and relevance-ranked free-text queries. - + - The Zebra server is our first step towards the development of a fully - configurable, open information system. Eventually, it will be paired - off with a powerful Z39.50 client to support complex information - management tasks within almost any application domain. We're making - the server available now because it's no fun to be in the open - information retrieval business all by yourself. We want to allow - people with interesting data to make their things - available in interesting ways, without having to start out - by implementing yet another protocol stack from scratch. + Zebra supports large databases (tens of millions of records, + tens of gigabytes of data). It allows safe, incremental + database updates on live systems. Because Zebra supports + the industry-standard information retrieval protocol, Z39.50, + you can search Zebra databases using an enormous variety of + programs and toolkits, both commercial and free, which understand + this protocol. Application libraries are available to allow + bespoke clients to be written in Perl, C, C++, Java, Tcl, Visual + Basic, Python, PHP and more - see + the ZOOM web site + for more information on some of these client toolkits. - + - This document is an introduction to the Zebra system. It will tell you - how to compile the software, and how to prepare your first database. - It also explains how the server can be configured to give you the + This document is an introduction to the Zebra system. It explains + how to compile the software, how to prepare your first database, + and how to configure the server to give you the functionality that you need. - - - If you find the software interesting, you should join the support - mailing-list by sending email to - zebra-request@indexdata.dk. - - Features - This is a list of some of the most important features of the - system. + This is an overview of some of Zebra's most important features: - + - - Supports updating - records can be added and deleted without - rebuilding the index from scratch. - The update procedure is tolerant to crashes or hard interrupts - during register updating - registers can be reconstructed following - a crash. - Registers can be safely updated even while users are accessing - the server. + Very large databases: logical files can be + automatically partitioned over multiple disks. + - - Supports large databases - files for indices, etc. can be - automatically partitioned over multiple disks. - + Arbitrarily complex records. The internal data format + is a structured format conceptually similar to XML or GRS-1, + which allows lists, nested structured data elements and + variant forms of data. + - - Supports arbitrarily complex records - base input format is an - SGML-like syntax which allows nested (structured) data elements, as - well as variant forms of data. - + Robust updating - records can be added and deleted ``on the fly'' + without rebuilding the index from scratch. + Records can be safely updated even while users are accessing + the server. + The update procedure is tolerant to crashes or hard interrupts + during database updating - data can be reconstructed following + a crash. + - - Supports random storage formats. A system of input filters driven by - regular expressions allows you to easily process most ASCII-based - data formats. SGML, ISO2709 (MARC), and raw text are also supported. - + Configurable to understand many input formats. + A system of input filters driven by + regular expressions allows most ASCII-based + data formats to be easily processed. + SGML, XML, ISO2709 (MARC), and raw text are also + supported. - - + + - Supports boolean queries as well as relevance-ranking (free-text) - searching. Right truncation and masking in terms are supported, as - well as full regular expressions. - + Searching supports a powerful combination of boolean queries as + well as relevance-ranking (free-text) queries. Truncation, + masking, full regular expression matching and "approximate + matching" (eg. spelling mistakes) are all handled. + - - - Supports multiple concrete syntaxes - for record exchange (depending on the configuration): GRS-1, SUTRS, - ISO2709 (*MARC). Records can be mapped between record syntaxes and - schema on the fly. - - + + Index-only databases: data can be, and usually is, imported + into Zebra's own storage, but Zebra can also refer to + external files, building and maintaining indexes of "live" + collections. + + - - Supports approximate matching in registers (ie. spelling mistakes, - etc). - + Zebra is written in portable C, so it runs on most Unix-like systems + as well as Windows NT. A binary distribution for Windows NT is + available at + , + and pre-built packages are available for some Linux + distributions: + Red Hat 7.x RPMs at + + and Debian packages at + @@ -119,161 +123,337 @@ - Protocol support: + Z39.50 protocol support: - - + - - Protocol facilities: Init, Search, Retrieve, Browse and Sort. - + Protocol facilities: Init, Search, Present (retrieval), + Segmentation (support for very large records), Delete, Scan + (index browsing), Sort, Close and support for the ``update'' + Extended Service to add or replace an existing XML record. + + - - Piggy-backed presents are honored in the search-request. - + Piggy-backed presents are honored in the search request - that + is, a subset of the found records can be returned directly with + a search response, enabling search and retrieval to happen in a + single round-trip. + - Named result sets are supported. - + - Easily configured to support different application profiles, with tables for attribute sets, tag sets, and abstract syntaxes. Additional tables control facilities such as element mappings to different schema (eg., GILS-to-USMARC). - + - - Complex composition specifications using Espec-1 are partially - supported (simple element requests only). - + Complex composition specifications using Espec-1 (partial support). + Element sets are defined using the Espec-1 capability, + and are specified in configuration files as simple element + requests (and, optionally, variant requests). + - - Element Set Names are defined using the Espec-1 capability of the - system, and are given in configuration files as simple element - requests (and possibly variant requests). - + Multiple record syntaxes + for data retrieval: GRS-1, SUTRS, + XML, ISO2709 (MARC), etc. Records can be mapped between record syntaxes + and schemas on the fly. - - + + + + + + + + + Applications + + Zebra has been deployed in numerous applications, in both the + academic and commercial worlds, in application domains as diverse + as bibliographic catalogues, geospatial information, structured + vocabulary browsing, government information locators, civic + information systems, environmental observations, museum information + and web indexes. + + + Notable applications include the following: + + + + DADS - the DTV Article Database Service + + DADS is a huge database of more than ten million records, totalling + over ten gigabytes of data. The records are metadata about academic + journal articles, primarily scientific; about 10% of these + metadata records link to the full text of the articles they + describe, a body of about a terabyte of information (although the + full text is not indexed.) + + + It allows students and researchers at DTU (Danmarks Tekniske + Universitet, the Technical College of Denmark) to find and order + articles from multiple databases in a single query. The database + contains literature on all engineering subjects. It's available + on-line through a web gateway, though currently only to registered + users. + + + More information can be found at + + + + + + NLI-Z39.50 - a Natural Language Interface for Libraries + + Fernuniversität Hagen in Germany have developed a natural + language interface for access to library databases. + + In order to evaluate this interface for recall and precision, they + chose Zebra as the basis for retrieval effectiveness. The Zebra + server contains a copy of the GIRT database, consisting of more + than 76000 records in SGML format (bibliographic records from + social science), which are mapped to MARC for presentation. + + + (GIRT is the German Indexing and Retrieval Testdatabase. It is a + standard German-language test database for intelligent indexing + and retrieval systems. See + ) + + + Evaluation will take place as part of the TREC/CLEF campaign 2003 + + + + For more information, contact Johannes Leveling + Johannes.Leveling@FernUni-Hagen.De + + + + + ULS (Union List of Serials) + + The M25 Systems Team + has created a union catalogue for the periodicals of the + twenty-one constituent libraries of the University of London and + the University of Westminster + (). + They have achieved this using an + unusual architecture, which they describe as a + ``non-distributed virtual union catalogue''. + + + The member libraries send in data files representing their + periodicals, including both brief bibliographic data and summary + holdings. Then 21 individual Z39.50 targets are created, each + using Zebra, and all mounted on the single hardware server. + The live service provides a web gateway allowing Z39.50 searching + of all of the targets or a selection of them. Zebra's small + footprint allows a relatively modest system to comfortably host + the 21 servers. + + + More information can be found at + + + + + + Various web indexes + + Zebra has been used by a variety of institutions to construct + indexes of large web sites, typically in the region of tens of + millions of pages. In this role, it functions somewhat similarly + to the engine of google or altavista, but for a selected intranet + or a subset of the whole Web. + + + For example, Liverpool University's web-search facility (see on + the home page at + + and many sub-pages) works by relevance-searching a Zebra database + which is populated by the Harvest-NG web-crawling software. + + + For more information on Liverpool university's intranet search + architecture, contact John Gilbertson + jgilbert@liverpool.ac.uk + + + Kang-Jin Lee + lee@arco.de, + has recently modified the Harvest web indexer to use Zebra as + its native repository engine. His comments on the switch over + from the old engine are revealing: +
- Some variant support (not fully implemented yet). - + The first results after some testing with Zebra are very + promising. The tests were done with around 220,000 SOIF files, + which occupies 1.6GB of disk space. - - - - Using the YAZ toolkit for the protocol implementation, the - server can utilise a plug-in XTI/mOSI implementation (not included) to - provide SR services over an OSI stack, as well as Z39.50 over TCP/IP. - + Building the index from scratch takes around one hour with Zebra + where [old-engine] needs around five hours. While [old-engine] + blocks search requests when updating its index, Zebra can still + answer search requests. + [...] + Zebra supports incremental indexing which will speed up indexing + even further. - - - - Zebra runs on most Unix-like systems as well as Windows NT - a binary - distribution for Windows NT is forthcoming - so far, the installation - requires MSVC++ to compile the system (we use version 5.0). - + While the search time of [old-engine] varies from some seconds + to some minutes depending how expensive the query is, Zebra + usually takes around one to three seconds, even for expensive + queries. + [...] + Zebra can search more than 100 times faster than [old-engine] + and can process multiple search requests simultaneously - - - - - - + + I am very happy to see such nice software available under GPL. + +
+ + - + + + + Support + + You can get support for Zebra from at least three sources. + + + First, there's the Zebra web site at + , + which always has the most recent version available for download. + If you have a problem with Zebra, the first thing to do is see + whether it's fixed in the current release. + + + Second, there's the Zebra mailing list. Its home page at + + includes a complete archive of all messages that have ever been + posted on the list. The Zebra mailing list is used both for + announcements from the authors (new + releases, bug fixes, etc.) and general discussion. You are welcome + to seek support there. Join by sending email to + zebra-request@indexdata.dk with the word + subscribe in the body of the message. + + + Third, it's possible to buy a commercial support contract, with + well defined service levels and response times, from Index Data. + See + + for details. + + + + - Future Work + Future Directions These are some of the plans that we have for the software in the near - and far future, approximately ordered after their relative importance. - Items marked with an - asterisk will be implemented before the - last beta release. + and far future, ordered approximately as we expect to work on them. - - - *Complete the support for variants. - - - *Finalize the data element include facility - to support multimedia data elements in records. + Improved support for XML in search and retrieval. Eventually, + the goal is for Zebra to pull double duty as a flexible + information retrieval engine and high-performance XML + repository. The recent addition of XPath searching is one + example of the kind of enhancement we're working on. - Add more sophisticated relevance ranking mechanisms. - Add support for soundex and stemming. - Add relevance feedback support. + Access to the search engine through SOAP/RPC API to allow the + construction of applications without requiring Z39.50 tools. + This will shortly be available by means of Index Data's + SRW-to-Z39.50 gateway, currently in beta test. - Complete EXPLAIN support. + Finalisation and documentation of Zebra's C programming + API, allowing updates, database management and other functions + not readily expressed in Z39.50. We will also consider + exposing the API through SOAP. - Add support for very large records by implementing segmentation and/or - variant pieces. + Support for the use of Perl both for access to the Zebra API + and for building extension ``plug-ins'' such as input filters. + The code for this has been contributed to the source tree by + Peter Popovics + pop@technomat.hu, + and is in the process of being integrated and tested. - Support the Item Update extended service of the protocol. + Improved free-text searching. We're first and foremost octet jockeys and + we're actively looking for organisations or people who'd like + to contribute experience in relevance ranking and text + searching. - - - We want to add a management system that allows you to - control your databases and configuration tables from a graphical - interface. - - Programmers thrive on user feedback. If you are interested in a facility that you don't see mentioned here, or if there's something - you think we could do better, please drop us a mail. + you think we could do better, please drop us a mail. Better still, + implement it and send us the patches. + + If you think it's all really neat, you're welcome to drop us a line - saying that, too. You'll find contact info at the end of this file. + saying that, too. You can email us on + info@indexdata.dk + or check the contact info at the end of this manual.