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14 <title>Pazpar2 - User's Guide and Reference</title>
16 <firstname>Sebastian</firstname><surname>Hammer</surname>
19 <firstname>Adam</firstname><surname>Dickmeiss</surname>
22 <firstname>Marc</firstname><surname>Cromme</surname>
25 <firstname>Jakub</firstname><surname>Skoczen</surname>
27 <releaseinfo>&version;</releaseinfo>
29 <year>©right-year;</year>
30 <holder>Index Data</holder>
34 Pazpar2 is a high-performance, user interface-independent, data
35 model-independent metasearching
36 middle-ware featuring merging, relevance ranking, record sorting,
40 This document is a guide and reference to Pazpar2 version &version;.
45 <imagedata fileref="common/id.png" format="PNG"/>
48 <imagedata fileref="common/id.eps" format="EPS"/>
55 <chapter id="introduction">
56 <title>Introduction</title>
58 Pazpar2 is a stand-alone metasearch client with a web-service API, designed
59 to be used either from a browser-based client (JavaScript, Flash, Java,
60 etc.), from server-side code, or any combination of the two.
61 Pazpar2 is a highly optimized client designed to
62 search many resources in parallel. It implements record merging,
63 relevance-ranking and sorting by arbitrary data content, and facet
64 analysis for browsing purposes. It is designed to be data model
65 independent, and is capable of working with MARC, DublinCore, or any
66 other <ulink url="&url.xml;">XML</ulink>-structured response format
67 -- <ulink url="&url.xslt;">XSLT</ulink> is used to normalize and extract
68 data from retrieval records for display and analysis. It can be used
69 against any server which supports the
70 <ulink url="&url.z39.50;">Z39.50</ulink> protocol. Proprietary
71 backend modules can be used to support a large number of other protocols
72 (please contact Index Data for further information about this).
75 Additional functionality such as
76 user management, attractive displays are expected to be implemented by
77 applications that use Pazpar2. Pazpar2 is user interface independent.
78 Its functionality is exposed through a simple REST-style web-service API,
79 designed to be simple to use from an Ajax-enabled browser, Flash
80 animation, Java applet, etc., or from a higher-level server-side language
81 like PHP or Java. Because session information can be shared between
82 browser-based logic and your server-side scripting, there is tremendous
83 flexibility in how you implement your business logic on top of Pazpar2.
86 Once you launch a search in Pazpar2, the operation continues behind the
87 scenes. Pazpar2 connects to servers, carries out searches, and
88 retrieves, deduplicates, and stores results internally. Your application
89 code may periodically inquire about the status of an ongoing operation,
90 and ask to see records or other result set facets. Result become
91 available immediately, and it is easy to build end-user interfaces which
92 feel extremely responsive, even when searching more than 100 servers
96 Pazpar2 is designed to be highly configurable. Incoming records are
97 normalized to XML/UTF-8, and then further normalized using XSLT to a
98 simple internal representation that is suitable for analysis. By
99 providing XSLT stylesheets for different kinds of result records, you
100 can tune Pazpar2 to work against different kinds of information
101 retrieval servers. Finally, metadata is extracted, in a configurable
102 way, from this internal record, to support display, merging, ranking,
103 result set facets, and sorting. Pazpar2 is not bound to a specific model
104 of metadata, such as DublinCore or MARC -- by providing the right
105 configuration, it can work with a number of different kinds of data in
106 support of many different applications.
109 Pazpar2 is designed to be efficient and scalable. You can set it up to
110 search several hundred targets in parallel, or you can use it to support
111 hundreds of concurrent users. It is implemented with the same attention
112 to performance and economy that we use in our indexing engines, so that
113 you can focus on building your application, without worrying about the
114 details of metasearch logic. You can devote all of your attention to
115 usability and let Pazpar2 do what it does best -- metasearch.
118 If you wish to connect to commercial or other databases which do not
119 support open standards, please contact Index Data. We have a licensing
120 agreement with a third party vendor which will enable Pazpar2 to access
121 thousands of online databases, in addition the vast number of catalogs
122 and online services that support the Z39.50 protocol.
125 Pazpar2 is our attempt to re-think the traditional paradigms for
126 implementing and deploying metasearch logic, with an uncompromising
127 approach to performance, and attempting to make maximum use of the
128 capabilities of modern browsers. The demo user interface that
129 accompanies the distribution is but one example. If you think of new
130 ways of using Pazpar2, we hope you'll share them with us, and if we
131 can provide assistance with regards to training, design, programming,
132 integration with different backends, hosting, or support, please don't
133 hesitate to contact us. If you'd like to see functionality in Pazpar2
134 that is not there today, please don't hesitate to contact us. It may
135 already be in our development pipeline, or there might be a
136 possibility for you to help out by sponsoring development time or
137 code. Either way, get in touch and we will give you straight answers.
143 Pazpar2 is covered by the GNU license version 2.
144 See <xref linkend="license"/> for further information.
148 <chapter id="installation">
149 <title>Installation</title>
151 The Pazpar2 package very small. It includes documentation as well
152 as the Pazpar2 server. The package also includes a simple user
153 interface test1 which consists of a single HTML page and a single
154 JavaScript file to illustrate the use of Pazpar2.
157 Pazpar2 depends on the following tools/libraries:
159 <varlistentry><term><ulink url="&url.yaz;">YAZ</ulink></term>
162 The popular Z39.50 toolkit for the C language.
163 YAZ <emphasis>must</emphasis> be compiled with Libxml2/Libxslt support.
167 <varlistentry><term><ulink url="&url.icu;">International
168 Components for Unicode (ICU)</ulink></term>
171 ICU provides Unicode support for non-English languages with
172 character sets outside the range of 7bit ASCII, like
173 Greek, Russian, German and French. Pazpar2 uses the ICU
174 Unicode character conversions, Unicode normalization, case
175 folding and other fundamental operations needed in
176 tokenization, normalization and ranking of records.
179 Compiling, linking, and usage of the ICU libraries is optional,
180 but strongly recommended for usage in an international
188 In order to compile Pazpar2, a C compiler which supports C99 or later
192 <section id="installation.unix">
193 <title>Installation on Unix (from Source)</title>
195 The latest source code for Pazpar2 is available from
196 <ulink url="&url.pazpar2.download;"/>.
197 Only few systems have none of the required
198 tools binary packages.
199 If, for example, Libxml2/libXSLT libraries
200 are already installed as development packages use these.
204 Ensure that the development libraries + header files are
205 available on your system before compiling Pazpar2. For installation
206 of YAZ, refer to the YAZ installation chapter.
209 gunzip -c pazpar2-version.tar.gz|tar xf -
217 The <literal>make install</literal> will install manpages as well as the
218 Pazpar2 server, <literal>pazpar2</literal>,
219 in PREFIX<literal>/sbin</literal>.
220 By default, PREFIX is <literal>/usr/local/</literal> . This can be
221 changed with configure option <option>--prefix</option>.
225 <section id="installation.test1">
226 <title>Installation of test1 interface</title>
228 In this section we outline how to install a simple interface that
229 is part of the Pazpar2 source package. Note that Debian users can
230 save time by just installing package <literal>pazpar2-test1</literal>.
233 A web server must be installed and running on the system, such as Apache.
237 Start the Pazpar2 daemon using the 'in-source' binary of the Pazpar2
241 cp pazpar2.cfg.dist pazpar2.cfg
242 ../src/pazpar2 -f pazpar2.cfg -t edu.xml
244 This will start a Pazpar2 listener on port 8004. It will proxy
245 HTTP requests to localhost - port 80, which we assume will be the regular
246 HTTP server on the system. Inspect and modify pazpar2.cfg as needed
247 if this is to be changed. The -t option specifies the list of targets
251 Make a new console and move to the other stuff.
252 For more information about pazpar2 options refer to the manpage.
256 The test1 UI is located in <literal>www/test1</literal>. Ensure this
257 directory is available to the web server by either copying
258 <literal>test1</literal> to the document root, create a symlink or
259 use Apache's <literal>Alias</literal> directive.
263 The interface test1 interface should now be available on port 8004.
266 If you don't see the test1 interface. See if test1 is really available
267 on the same URL but on port 80. If it's not, the Apache configuration
268 (or other) is not correct.
271 In order to use Apache as frontend for the interface on port 80
272 for public access etc., refer to
273 <xref linkend="installation.apache2proxy"/>.
277 <section id="installation.debian">
278 <title>Installation on Debian GNU/Linux</title>
280 Index Data provides Debian packages for Pazpar2. These are prepared
281 for Debian versions Etch and Lenny (as of 2007).
282 These packages are available at
283 <ulink url="&url.pazpar2.download.debian;"/>.
287 <section id="installation.apache2proxy">
288 <title>Apache 2 Proxy</title>
291 <ulink url="http://httpd.apache.org/docs/2.2/mod/mod_proxy.html">
293 </ulink> which allows Pazpar2 to become a backend to an Apache 2
294 based web service. The Apache 2 proxy must operate in the
295 <emphasis>Reverse</emphasis> Proxy mode.
299 On a Debian based Apache 2 system, the relevant modules can
302 sudo a2enmod proxy_http
307 Traditionally Pazpar2 interprets URL paths with suffix
308 <literal>/search.pz2</literal>.
311 url="http://httpd.apache.org/docs/2.2/mod/mod_proxy.html#proxypass"
312 >ProxyPass</ulink> directive of Apache must be used to map a URL path
313 the the Pazpar2 server (listening port).
318 The ProxyPass directive takes a prefix rather than
319 a suffix as URL path. It is important that the Java Script code
320 uses the prefix given for it.
324 <example id="installation.apache2proxy.example">
325 <title>Apache 2 proxy configuration</title>
327 If Pazpar2 is running on port 8004 and the portal is using
328 <filename>search.pz2</filename> inside portal in directory
329 <filename>/myportal/</filename> we could use the following
330 Apache 2 configuration:
333 <IfModule mod_proxy.c>
337 AddDefaultCharset off
342 ProxyPass /myportal/search.pz2 http://localhost:8004/search.pz2
353 <title>Using Pazpar2</title>
355 This chapter provides a general introduction to the use and
356 deployment of Pazpar2.
359 <section id="architecture">
360 <title>Pazpar2 and your systems architecture</title>
362 Pazpar2 is designed to provide asynchronous, behind-the-scenes
363 metasearching functionality to your application, exposing this
364 functionality using a simple webservice API that can be accessed
365 from any number of development environments. In particular, it is
366 possible to combine Pazpar2 either with your server-side dynamic
367 website scripting, with scripting or code running in the browser, or
368 with any combination of the two. Pazpar2 is an excellent tool for
369 building advanced, Ajax-based user interfaces for metasearch
370 functionality, but it isn't a requirement -- you can choose to use
371 Pazpar2 entirely as a backend to your regular server-side scripting.
372 When you do use Pazpar2 in conjunction
373 with browser scripting (JavaScript/Ajax, Flash, applets,
374 etc.), there are special considerations.
378 Pazpar2 implements a simple but efficient HTTP server, and it is
379 designed to interact directly with scripting running in the browser
380 for the best possible performance, and to limit overhead when
381 several browser clients generate numerous webservice requests.
382 However, it is still desirable to use a conventional webserver,
383 such as Apache, to serve up graphics, HTML documents, and
384 server-side scripting. Because the security sandbox environment of
385 most browser-side programming environments only allows communication
386 with the server from which the enclosing HTML page or object
387 originated, Pazpar2 is designed so that it can act as a transparent
388 proxy in front of an existing webserver (see <xref
389 linkend="pazpar2_conf"/> for details).
390 In this mode, all regular
391 HTTP requests are transparently passed through to your webserver,
392 while Pazpar2 only intercepts search-related webservice requests.
396 If you want to expose your combined service on port 80, you can
397 either run your regular webserver on a different port, a different
398 server, or a different IP address associated with the same server.
402 Pazpar2 can also work behind
403 a reverse Proxy. Refer to <xref linkend="installation.apache2proxy"/>)
404 for more information.
405 This allows your existing HTTP server to operate on port 80 as usual.
406 Pazpar2 can be started on another (internal) port.
410 Sometimes, it may be necessary to implement functionality on your
411 regular webserver that makes use of search results, for example to
412 implement data import functionality, emailing results, history
413 lists, personal citation lists, interlibrary loan functionality
414 ,etc. Fortunately, it is simple to exchange information between
415 Pazpar2, your browser scripting, and backend server-side scripting.
416 You can send a session ID and possibly a record ID from your browser
417 code to your server code, and from there use Pazpar2s webservice API
418 to access result sets or individual records. You could even 'hide'
419 all of Pazpar2s functionality between your own API implemented on
420 the server-side, and access that from the browser or elsewhere. The
421 possibilities are just about endless.
425 <section id="data_model">
426 <title>Your data model</title>
428 Pazpar2 does not have a preconceived model of what makes up a data
429 model. There are no assumption that records have specific fields or
430 that they are organized in any particular way. The only assumption
431 is that data comes packaged in a form that the software can work
432 with (presently, that means XML or MARC), and that you can provide
433 the necessary information to massage it into Pazpar2's internal
438 Handling retrieval records in Pazpar2 is a two-step process. First,
439 you decide which data elements of the source record you are
440 interested in, and you specify any desired massaging or combining of
441 elements using an XSLT stylesheet (MARC records are automatically
442 normalized to <ulink url="&url.marcxml;">MARCXML</ulink> before this step).
443 If desired, you can run multiple XSLT stylesheets in series to accomplish
444 this, but the output of the last one should be a representation of the
445 record in a schema that Pazpar2 understands.
449 The intermediate, internal representation of the record looks like
452 <record xmlns="http://www.indexdata.com/pazpar2/1.0"
453 mergekey="title The Shining author King, Stephen">
455 <metadata type="title">The Shining</metadata>
457 <metadata type="author">King, Stephen</metadata>
459 <metadata type="kind">ebook</metadata>
461 <!-- ... and so on -->
465 As you can see, there isn't much to it. There are really only a few
466 important elements to this file.
470 Elements should belong to the namespace
471 <literal>http://www.indexdata.com/pazpar2/1.0</literal>.
472 If the root node contains the
473 attribute 'mergekey', then every record that generates the same
474 merge key (normalized for case differences, white space, and
475 truncation) will be joined into a cluster. In other words, you
476 decide how records are merged. If you don't include a merge key,
477 records are never merged. The 'metadata' elements provide the meat
478 of the elements -- the content. the 'type' attribute is used to
479 match each element against processing rules that determine what
480 happens to the data element next.
484 The next processing step is the extraction of metadata from the
485 intermediate representation of the record. This is governed by the
486 'metadata' elements in the 'service' section of the configuration
487 file. See <xref linkend="config-server"/> for details. The metadata
488 in the retrieval record ultimately drives merging, sorting, ranking,
489 the extraction of browse facets, and display, all configurable.
493 <section id="client">
494 <title>Client development overview</title>
496 You can use Pazpar2 from any environment that allows you to use
497 webservices. The initial goal of the software was to support
498 Ajax-based applications, but there literally are no limits to what
499 you can do. You can use Pazpar2 from Javascript, Flash, Java, etc.,
500 on the browser side, and from any development environment on the
501 server side, and you can pass session tokens and record IDs freely
502 around between these environments to build sophisticated applications.
503 Use your imagination.
507 The webservice API of Pazpar2 is described in detail in <xref
508 linkend="pazpar2_protocol"/>.
512 In brief, you use the 'init' command to create a session, a
513 temporary workspace which carries information about the current
514 search. You start a new search using the 'search' command. Once the
515 search has been started, you can follow its progress using the
516 'stat', 'bytarget', 'termlist', or 'show' commands. Detailed records
517 can be fetched using the 'record' command.
523 <section id="nonstandard">
524 <title>Connecting to non-standard resources</title>
526 Pazpar2 uses Z39.50 as its switchboard language -- i.e. as far as it
527 is concerned, all resources speak Z39.50. It is, however, equipped
528 to handle a broad range of different server behavior, through
529 configurable query mapping and record normalization. If you develop
530 configuration, stylesheets, etc., for a new type of resources, we
531 encourage you to share your work. But you can also use Pazpar2 to
532 connect to hundreds of resources that do not support standard
537 For a growing number of resources, Z39.50 is all you need. Over the
538 last few years, a number of commercial, full-text resources have
539 implemented Z39.50. These can be used through Pazpar2 with little or
540 no effort. Resources that use non-standard record formats will
541 require a bit of XSLT work, but that's all.
545 But what about resources that don't support Z39.50 at all? The NISO
546 SRU (MXG) protocol is slowly gathering steam. Other resources might
547 support OpenSearch, private, XML/HTTP-based protocols, or something
548 else entirely. Some databases exist only as web user interfaces and
549 will require screen-scraping. Still others exist only as static
550 files, or perhaps as databases supporting the OAI-PMH protocol.
551 There is hope! Read on.
555 Index Data continues to advocate the support of open standards. We
556 work with database vendors to support standards, so you don't have
557 to worry about programming against non-standard services. We also
558 provide tools (see <ulink
559 url="http://www.indexdata.com/simpleserver">SimpleServer</ulink>)
560 which make it comparatively easy to build gateways against servers
561 with non-standard behavior. Again, we encourage you to share any
562 work you do in this direction.
566 But the bottom line is that working with non-standard resources in
567 metasearching is really, really hard. If you want to build a
568 project with Pazpar2, and you need access to resources with
569 non-standard interfaces, we can help. We run gateways to more than
570 2,000 popular, commercial databases and other resources,
572 to plug them directly into Pazpar2. For a small annual fee per
573 database, we can help you establish connections to your licensed
574 resources. Meanwhile, you can help! If you build your own
575 standards-compliant gateways, host them for others, or share the
576 code! And tell your vendors that they can save everybody money and
577 increase the appeal of their resources by supporting standards.
581 There are those who will ask us why we are using Z39.50 as our
582 switchboard language rather than a different protocol. Basically,
583 we believe that Z39.50 is presently the most widely implemented
584 information retrieval protocol that has the level of functionality
585 required to support a good metasearching experience (structured
586 searching, structured, well-defined results). It is also compact and
587 efficient, and there is a very broad range of tools available to
592 <section id="unicode">
593 <title>Unicode Compliance</title>
595 Pazpar2 is Unicode compliant and language and locale aware but relies
596 on character encoding for the targets to be specified correctly if
597 the targets themselves are not UTF-8 based (most aren't).
598 Just a few bad behaving targets can spoil the search experience
599 considerably if for example Greek, Russian or otherwise non 7-bit ASCII
600 search terms are entered. In these cases some targets return
601 records irrelevant to the query, and the result screens will be
602 cluttered with noise.
605 While noise from misbehaving targets can not be removed, it can
606 be reduced using truly Unicode based ranking. This is an
607 option which is available to the system administrator if ICU
608 support is compiled into Pazpar2, see
609 <xref linkend="installation"/> for details.
612 In addition, the ICU tokenization and normalization rules must
613 be defined in the master configuration file described in
614 <xref linkend="config-server"/>.
618 </chapter> <!-- Using Pazpar2 -->
620 <reference id="reference">
621 <title>Reference</title>
622 <partintro id="reference-introduction">
624 The material in this chapter is drawn directly from the individual
631 <appendix id="license"><title>License</title>
633 <section id="gpl"><title>GPL</title>
637 Copyright © ©right-year; Index Data.
641 Pazpar2 is free software; you can redistribute it and/or modify it under
642 the terms of the GNU General Public License as published by the Free
643 Software Foundation; either version 2, or (at your option) any later
648 Pazpar2 is distributed in the hope that it will be useful, but WITHOUT ANY
649 WARRANTY; without even the implied warranty of MERCHANTABILITY or
650 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
655 You should have received a copy of the GNU General Public License
656 along with Pazpar2; see the file LICENSE. If not, write to the
657 Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
662 GNU GENERAL PUBLIC LICENSE
665 Copyright (C) 1989, 1991 Free Software Foundation, Inc.
666 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
667 Everyone is permitted to copy and distribute verbatim copies
668 of this license document, but changing it is not allowed.
672 The licenses for most software are designed to take away your
673 freedom to share and change it. By contrast, the GNU General Public
674 License is intended to guarantee your freedom to share and change free
675 software--to make sure the software is free for all its users. This
676 General Public License applies to most of the Free Software
677 Foundation's software and to any other program whose authors commit to
678 using it. (Some other Free Software Foundation software is covered by
679 the GNU Library General Public License instead.) You can apply it to
682 When we speak of free software, we are referring to freedom, not
683 price. Our General Public Licenses are designed to make sure that you
684 have the freedom to distribute copies of free software (and charge for
685 this service if you wish), that you receive source code or can get it
686 if you want it, that you can change the software or use pieces of it
687 in new free programs; and that you know you can do these things.
689 To protect your rights, we need to make restrictions that forbid
690 anyone to deny you these rights or to ask you to surrender the rights.
691 These restrictions translate to certain responsibilities for you if you
692 distribute copies of the software, or if you modify it.
694 For example, if you distribute copies of such a program, whether
695 gratis or for a fee, you must give the recipients all the rights that
696 you have. You must make sure that they, too, receive or can get the
697 source code. And you must show them these terms so they know their
700 We protect your rights with two steps: (1) copyright the software, and
701 (2) offer you this license which gives you legal permission to copy,
702 distribute and/or modify the software.
704 Also, for each author's protection and ours, we want to make certain
705 that everyone understands that there is no warranty for this free
706 software. If the software is modified by someone else and passed on, we
707 want its recipients to know that what they have is not the original, so
708 that any problems introduced by others will not reflect on the original
709 authors' reputations.
711 Finally, any free program is threatened constantly by software
712 patents. We wish to avoid the danger that redistributors of a free
713 program will individually obtain patent licenses, in effect making the
714 program proprietary. To prevent this, we have made it clear that any
715 patent must be licensed for everyone's free use or not licensed at all.
717 The precise terms and conditions for copying, distribution and
720 GNU GENERAL PUBLIC LICENSE
721 TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
723 0. This License applies to any program or other work which contains
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730 language. (Hereinafter, translation is included without limitation in
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741 source code as you receive it, in any medium, provided that you
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748 You may charge a fee for the physical act of transferring a copy, and
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751 2. You may modify your copy or copies of the Program or any portion
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759 b) You must cause any work that you distribute or publish, that in
760 whole or in part contains or is derived from the Program or any
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773 the Program is not required to print an announcement.)
775 These requirements apply to the modified work as a whole. If
776 identifiable sections of that work are not derived from the Program,
777 and can be reasonably considered independent and separate works in
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779 sections when you distribute them as separate works. But when you
780 distribute the same sections as part of a whole which is a work based
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782 this License, whose permissions for other licensees extend to the
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793 the scope of this License.
795 3. You may copy and distribute the Program (or a work based on it,
796 under Section 2) in object code or executable form under the terms of
797 Sections 1 and 2 above provided that you also do one of the following:
799 a) Accompany it with the complete corresponding machine-readable
800 source code, which must be distributed under the terms of Sections
801 1 and 2 above on a medium customarily used for software interchange; or,
803 b) Accompany it with a written offer, valid for at least three
804 years, to give any third party, for a charge no more than your
805 cost of physically performing source distribution, a complete
806 machine-readable copy of the corresponding source code, to be
807 distributed under the terms of Sections 1 and 2 above on a medium
808 customarily used for software interchange; or,
810 c) Accompany it with the information you received as to the offer
811 to distribute corresponding source code. (This alternative is
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814 an offer, in accord with Subsection b above.)
816 The source code for a work means the preferred form of the work for
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818 code means all the source code for all modules it contains, plus any
819 associated interface definition files, plus the scripts used to
820 control compilation and installation of the executable. However, as a
821 special exception, the source code distributed need not include
822 anything that is normally distributed (in either source or binary
823 form) with the major components (compiler, kernel, and so on) of the
824 operating system on which the executable runs, unless that component
825 itself accompanies the executable.
827 If distribution of executable or object code is made by offering
828 access to copy from a designated place, then offering equivalent
829 access to copy the source code from the same place counts as
830 distribution of the source code, even though third parties are not
831 compelled to copy the source along with the object code.
833 4. You may not copy, modify, sublicense, or distribute the Program
834 except as expressly provided under this License. Any attempt
835 otherwise to copy, modify, sublicense or distribute the Program is
836 void, and will automatically terminate your rights under this License.
837 However, parties who have received copies, or rights, from you under
838 this License will not have their licenses terminated so long as such
839 parties remain in full compliance.
841 5. You are not required to accept this License, since you have not
842 signed it. However, nothing else grants you permission to modify or
843 distribute the Program or its derivative works. These actions are
844 prohibited by law if you do not accept this License. Therefore, by
845 modifying or distributing the Program (or any work based on the
846 Program), you indicate your acceptance of this License to do so, and
847 all its terms and conditions for copying, distributing or modifying
848 the Program or works based on it.
850 6. Each time you redistribute the Program (or any work based on the
851 Program), the recipient automatically receives a license from the
852 original licensor to copy, distribute or modify the Program subject to
853 these terms and conditions. You may not impose any further
854 restrictions on the recipients' exercise of the rights granted herein.
855 You are not responsible for enforcing compliance by third parties to
858 7. If, as a consequence of a court judgment or allegation of patent
859 infringement or for any other reason (not limited to patent issues),
860 conditions are imposed on you (whether by court order, agreement or
861 otherwise) that contradict the conditions of this License, they do not
862 excuse you from the conditions of this License. If you cannot
863 distribute so as to satisfy simultaneously your obligations under this
864 License and any other pertinent obligations, then as a consequence you
865 may not distribute the Program at all. For example, if a patent
866 license would not permit royalty-free redistribution of the Program by
867 all those who receive copies directly or indirectly through you, then
868 the only way you could satisfy both it and this License would be to
869 refrain entirely from distribution of the Program.
871 If any portion of this section is held invalid or unenforceable under
872 any particular circumstance, the balance of the section is intended to
873 apply and the section as a whole is intended to apply in other
876 It is not the purpose of this section to induce you to infringe any
877 patents or other property right claims or to contest validity of any
878 such claims; this section has the sole purpose of protecting the
879 integrity of the free software distribution system, which is
880 implemented by public license practices. Many people have made
881 generous contributions to the wide range of software distributed
882 through that system in reliance on consistent application of that
883 system; it is up to the author/donor to decide if he or she is willing
884 to distribute software through any other system and a licensee cannot
887 This section is intended to make thoroughly clear what is believed to
888 be a consequence of the rest of this License.
890 8. If the distribution and/or use of the Program is restricted in
891 certain countries either by patents or by copyrighted interfaces, the
892 original copyright holder who places the Program under this License
893 may add an explicit geographical distribution limitation excluding
894 those countries, so that distribution is permitted only in or among
895 countries not thus excluded. In such case, this License incorporates
896 the limitation as if written in the body of this License.
898 9. The Free Software Foundation may publish revised and/or new versions
899 of the General Public License from time to time. Such new versions will
900 be similar in spirit to the present version, but may differ in detail to
901 address new problems or concerns.
903 Each version is given a distinguishing version number. If the Program
904 specifies a version number of this License which applies to it and "any
905 later version", you have the option of following the terms and conditions
906 either of that version or of any later version published by the Free
907 Software Foundation. If the Program does not specify a version number of
908 this License, you may choose any version ever published by the Free Software
911 10. If you wish to incorporate parts of the Program into other free
912 programs whose distribution conditions are different, write to the author
913 to ask for permission. For software which is copyrighted by the Free
914 Software Foundation, write to the Free Software Foundation; we sometimes
915 make exceptions for this. Our decision will be guided by the two goals
916 of preserving the free status of all derivatives of our free software and
917 of promoting the sharing and reuse of software generally.
921 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
922 FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
923 OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
924 PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
925 OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
926 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
927 TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
928 PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
929 REPAIR OR CORRECTION.
931 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
932 WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
933 REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
934 INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
935 OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
936 TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
937 YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
938 PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
939 POSSIBILITY OF SUCH DAMAGES.
941 END OF TERMS AND CONDITIONS
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