Added section about using Apache 2's Proxy.

[pazpar2-moved-to-github.git] / doc / book.xml

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<!-- $Id: book.xml,v 1.15 2007-06-04 11:00:54 adam Exp $ -->
<book id="book">
 <bookinfo>
  <title>Pazpar2 - User's Guide and Reference</title>
  <author>
   <firstname>Sebastian</firstname><surname>Hammer</surname>
  </author>
  <author>
   <firstname>Adam</firstname><surname>Dickmeiss</surname>
  </author>
  <author>
   <firstname>Marc</firstname><surname>Cromme</surname>
  </author>
  <releaseinfo>&version;</releaseinfo>
  <copyright>
   <year>&copyright-year;</year>
   <holder>Index Data</holder>
  </copyright>
  <abstract>
   <simpara>
    Pazpar2 is a high-performance, user interface-independent, data
    model-independent metasearching
    middleware featuring merging, relevance ranking, record sorting, 
    and faceted results.
   </simpara>
   <simpara>
    This document is a guide and reference to Pazpar version &version;.
   </simpara>
   <simpara>
    <inlinemediaobject>
     <imageobject>
      <imagedata fileref="common/id.png" format="PNG"/>
   </imageobject>
    <imageobject>
     <imagedata fileref="common/id.eps" format="EPS"/>
   </imageobject>
   </inlinemediaobject>
   </simpara>
  </abstract>
 </bookinfo>
 
 <chapter id="introduction">
  <title>Introduction</title>
  <para>
   Pazpar2 is a stand-alone metasearch client with a webservice API, designed
   to be used either from a browser-based client (JavaScript, Flash, Java,
   etc.), from from server-side code, or any combination of the two.
   Pazpar2 is a highly optimized client designed to
   search many resources in parallel. It implements record merging,
   relevance-ranking and sorting by arbitrary data content, and facet
   analysis for browsing purposes. It is designed to be data model
   independent, and is capable of working with MARC, DublinCore, or any
   other XML-structured response format -- XSLT is used to normalize and extract
   data from retrieval records for display and analysis. It can be used
   against any server which supports the Z39.50 protocol. Proprietary
   backend modules can be used to support a large number of other protocols
   (please contact Index Data for further information about this).
  </para>
  <para>
   Additional functionality such as
   user management, attractive displays are expected to be implemented by
   applications that use pazpar2. Pazpar2 is user interface independent.
   Its functionality is exposed through a simple REST-style webservice API,
   designed to be simple to use from an Ajax-enbled browser, Flash
   animation, Java applet, etc., or from a higher-level server-side language
   like PHP or Java. Because session information can be shared between
   browser-based logic and your server-side scripting, there is tremendous
   flexibility in how you implement your business logic on top of pazpar2.
  </para>
  <para>
   Once you launch a search in pazpar2, the operation continues behind the
   scenes. Pazpar2 connects to servers, carries out searches, and
   retrieves, deduplicates, and stores results internally. Your application
   code may periodically inquire about the status of an ongoing operation,
   and ask to see records or other result set facets. Result become
   available immediately, and it is easy to build end-user interfaces which
   feel extremely responsive, even when searching more than 100 servers
   concurrently.
  </para>
  <para>
   Pazpar2 is designed to be highly configurable. Incoming records are
   normalized to XML/UTF-8, and then further normalized using XSLT to a
   simple internal representation that is suitable for analysis. By
   providing XSLT stylesheets for different kinds of result records, you
   can tune pazpar2 to work against different kinds of information
   retrieval servers. Finally, metadata is extracted, in a configurable
   way, from this internal record, to support display, merging, ranking,
   result set facets, and sorting. Pazpar2 is not bound to a specific model
   of metadata, such as DublinCore or MARC -- by providing the right
   configuration, it can work with a number of different kinds of data in
   support of many different applications.
  </para>
  <para>
   Pazpar2 is designed to be efficient and scalable. You can set it up to
   search several hundred targets in parallel, or you can use it to support
   hundreds of concurrent users. It is implemented with the same attention
   to performance and economy that we use in our indexing engines, so that
   you can focus on building your application, without worrying about the
   details of metasearch logic. You can devote all of your attention to
   usability and let pazpar2 do what it does best -- metasearch.
  </para>
  <para>
   If you wish to connect to commercial or other databases which do not
   support open standards, please contact Index Data. We have a licensing
   agreement with a third party vendor which will enable pazpar2 to access
   thousands of online databases, in addition the vast number of catalogs
   and online services that support the Z39.50 protocol.
  </para>
  <para>
   Pazpar2 is our attempt to re-think the traditional paradigms for
   implementing and deploying metasearch logic, with an uncompromising
   approach to performance, and attempting to make maximum use of the
   capabilities of modern browsers. The demo user interface that
   accompanies the distribution is but one example. If you think of new
   ways of using pazpar2, we hope you'll share them with us, and if we
   can provide assistance with regards to training, design, programming,
   integration with different backends, hosting, or support, please don't
   hesitate to contact us. If you'd like to see functionality in pazpar2
   that is not there today, please don't hesitate to contact us. It may
   already be in our development pipeline, or there might be a
   possibility for you to help out by sponsoring development time or
   code. Either way, get in touch and we will give you straight answers.
  </para>
  <para>
   Enjoy!
  </para>
  <para>
   Pazpar2 is covered by the GNU license version 2.
   See <xref linkend="license"/> for further information.
  </para>
 </chapter>

 <chapter id="installation">
  <title>Installation</title>
  <para>
   Pazpar2 depends on the following tools/libraries:
   <variablelist>
    <varlistentry><term><ulink url="&url.yaz;">YAZ</ulink></term>
     <listitem>
      <para>
       The popular Z39.50 toolkit for the C language. YAZ must be
       compiled with Libxml2/Libxslt support.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry><term><ulink url="&url.icu;">International
       Components for Unicode (ICU)</ulink></term>
     <listitem>
      <para>
       ICU provides Unicode support for non-english languages with
       character sets outside the range of 7bit ASCII, like
       Greek, Russian, German and Frensh. Pazpar2 uses the ICU
       unicode character conversions, unicode normalization, case
       folding and other fundamental operations needed in
       tokenization, normalization and ranking of records. 
      </para>
      <para>
       Compiling, linking, and usage of the ICU libraries is optional,
       but strongly recommended for usage in an international
       environment.  
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
  <para>
   In order to compile Pazpar2 an ANSI C compiler is
   required. The requirements should be the same as for YAZ.
  </para>

  <section id="installation.unix">
   <title>Installation on Unix (from Source)</title>
   <para>
    Here is a quick step-by-step guide on how to compile the
    tools that Pazpar2 uses. Only few systems have none of the required
    tools binary packages. If, for example, Libxml2/libxslt are already
    installed as development packages use these.
   </para>
   
   <para>
    Ensure that the development libraries + header files are
    available on your system before compiling Pazpar2. For installation
    of YAZ, refer to the YAZ installation chapter.
   </para>
   <screen>
    gunzip -c pazpar2-version.tar.gz|tar xf -
    cd pazpar2-version
    ./configure
    make
    su
    make install
   </screen>
  </section>

  <section id="installation.debian">
   <title>Installation on Debian GNU/Linux</title>
   <para>
    All dependencies for Pazpar2 are available as 
    <ulink url="&url.debian;">Debian</ulink>
    packages for the sarge (stable in 2005) and etch (testing in 2005)
    distributions.
   </para>
   <para>
    The procedures for Debian based systems, such as
    <ulink url="&url.ubuntu;">Ubuntu</ulink> is probably similar
   </para>
   <screen>
    apt-get install libyaz-dev
    apt-get install libicu36-dev
   </screen>
   <para>
    With these packages installed, the usual configure + make
    procedure can be used for Pazpar2 as outlined in
    <xref linkend="installation.unix"/>.
   </para>
  </section>

  <section id="installation.apache2proxy">
   <title>Apache 2 Proxy</title>
   <para>
    Apache 2 has a 
    <ulink url="http://httpd.apache.org/docs/2.2/mod/mod_proxy.html">
     proxy module
    </ulink> which allows Pazpar2 to become a backend to an Apache 2
    based web service. The Apache 2 proxy must operate in the
    <emphasis>Reverse</emphasis> Proxy mode.
   </para>
   
   <para>
    On a Debian based Apache 2 system, the relevant modules can
    be enabled with:
    <screen>
     sudo a2enmod proxy_http
    </screen>
   </para>

   <para>
    Traditionnally Pazpar2 interprets URL paths with suffix 
    <literal>/search.pz2</literal>.
    The <literal>ProxyPass</literal> must be configured with this
    path and the address of the Pazpar2 server (listening port).
   </para>

   <note>
    <para>
     Since the ProxyPass directive takes a prefix rather than
     a suffix as URL path it is important that the Java Script code
     uses <literal>/search.pz2</literal> rather than just
     <literal>search.pz2</literal>.
    </para>
   </note>

   <example id="installation.apache2proxy.example">
    <title>Apache 2 proxy configuration</title>
    <para>
     If Pazpar2 is running on port 9004 we can use the following
     Apache 2 configuration:

     <screen><![CDATA[
      <IfModule mod_proxy.c>
       ProxyRequests Off
      
       <Proxy *>
        AddDefaultCharset off
        Order deny,allow
        Allow from all
       </Proxy>
      
       ProxyPass /search.pz2 http://localhost:9004/search.pz2
       ProxyVia Off
      </IfModule>
      ]]></screen>
    </para>
   </example>
  </section>

 </chapter>

 <chapter id="using">
  <title>Using pazpar2</title>
  <para>
   This chapter provides a general introduction to the use and
   deployment of pazpar2. 
  </para>

  <section id="architecture">
   <title>Pazpar2 and your systems architecture</title>
   <para>
    Pazpar2 is designed to provide asynchronous, behind-the-scenes
    metasearching functionality to your application, exposing this
    functionality using a simple webservice API that can be accessed
    from any number of development environments. In particular, it is
    possible to combine pazpar2 either with your server-side dynamic
    website scripting, with scripting or code running in the browser, or
    with any combination of the two. Pazpar2 is an excellent tool for
    building advanced, Ajax-based user interfaces for metasearch
    functionality, but it isn't a requirement -- you can choose to use
    pazpar2 entirely as a backend to your regular server-side scripting.
    When you do use pazpar2 in conjunction
    with browser scripting (JavaScript/Ajax, Flash, applets,
    etc.), there are    special considerations.
   </para>

   <para>
    Pazpar2 implements a simple but efficient HTTP server, and it is
    designed to interact directly with scripting running in the browser
    for the best possible performance, and to limit overhead when
    several browser clients generate numerous webservice requests.
    However, it is still desirable to use a conventional webserver,
    such as Apache, to serve up graphics, HTML documents, and
    server-side scripting. Because the security sandbox environment of
    most browser-side programming environments only allows communication
    with the server from which the enclosing HTML page or object
    originated, pazpar2 is designed so that it can act as a transparent
    proxy in front of an existing webserver (see <xref
     linkend="pazpar2_conf"/> for details). In this mode, all regular
    HTTP requests are transparently passed through to your webserver,
    while pazpar2 only intercepts search-related webservice requests.
   </para>

   <para>
    If you want to expose your combined service on port 80, you can
    either run your regular webserver on a different port, a different
    server, or a different IP address associated with the same server.
   </para>

   <para>
    Sometimes, it may be necessary to implement functionality on your
    regular webserver that makes use of search results, for example to
    implement data import functionality, emailing results, history
    lists, personal citation lists, interlibrary loan functionality
    ,etc. Fortunately, it is simple to exchange information between
    pazpar2, your browser scripting, and backend server-side scripting.
    You can send a session ID and possibly a record ID from your browser
    code to your server code, and from there use pazpar2s webservice API
    to access result sets or individual records. You could even 'hide'
    all of pazpar2s functionality between your own API implemented on
    the server-side, and access that from the browser or elsewhere. The
    possibilities are just about endless.
   </para>
  </section>

  <section id="data_model">
   <title>Your data model</title>
   <para>
    Pazpar2 does not have a preconceived model of what makes up a data
    model. There are no assumption that records have specific fields or
    that they are organized in any particular way. The only assumption
    is that data comes packaged in a form that the software can work
    with (presently, that means XML or MARC), and that you can provide
    the necessary information to massage it into pazpar2's internal
    record abstraction.
   </para>

   <para>
    Handling retrieval records in pazpar2 is a two-step process. First,
    you decide which data elements of the source record you are
    interested in, and you specify any desired massaging or combining of
    elements using an XSLT stylesheet (MARC records are automatically
    normalized to MARCXML before this step). If desired, you can run
    multiple XSLT stylesheets in series to accomplish this, but the
    output of the last one should be a representation of the record in a
    schema that pazpar2 understands.
   </para>

   <para>
    The intermediate, internal representation of the record looks like
    this:
    <screen><![CDATA[
     <record   xmlns="http://www.indexdata.com/pazpar2/1.0"
     mergekey="title The Shining author King, Stephen">

     <metadata type="title">The Shining</metadata>

     <metadata type="author">King, Stephen</metadata>

     <metadata type="kind">ebook</metadata>

     <!-- ... and so on -->
    </record>
     ]]></screen>

    As you can see, there isn't much to it. There are really only a few
    important elements to this file.
   </para>

   <para>
    Elements should belong to the namespace
    http://www.indexdata.com/pazpar2/1.0. If the root node contains the
    attribute 'mergekey', then every record that generates the same
    merge key (normalized for case differences, white space, and
    truncation) will be joined into a cluster. In other words, you
    decide how records are merged. If you don't include a merge key,
    records are never merged. The 'metadata' elements provide the meat
    of the elements -- the content. the 'type' attribute is used to
    match each element against processing rules that determine what
    happens to the data element next.
   </para>

   <para>
    The next processing step is the extraction of metadata from the
    intermediate representation of the record. This is governed by the
    'metadata' elements in the 'service' section of the configuration
    file. See <xref linkend="config-server"/> for details. The metadata
    in the retrieval record ultimately drives merging, sorting, ranking,
    the extraction of browse facets, and display, all configurable.
   </para>
  </section>

  <section id="client">
   <title>Client development overview</title>
   <para>
    You can use pazpar2 from any environment that allows you to use
    webservices. The initial goal of the software was to support
    Ajax-based applications, but there literally are no limits to what
    you can do. You can use pazpar2 from Javascript, Flash, Java, etc.,
    on the browser side, and from any development environment on the
    server side, and you can pass session tokens and record IDs freely
    around between these environments to build sophisticated applications.
    Use your imagination.
   </para>

   <para>
    The webservice API of pazpar2 is described in detail in <xref
     linkend="pazpar2_protocol"/>.
   </para>

   <para>
    In brief, you use the 'init' command to create a session, a
    temporary workspace which carries information about the current
    search. You start a new search using the 'search' command. Once the
    search has been started, you can follow its progress using the
    'stat', 'bytarget', 'termlist', or 'show' commands. Detailed records
    can be fetched using the 'record' command.
   </para>
  </section>

  <section id="nonstandard">
   <title>Connecting to non-standard resources</title>
   <para>
    Pazpar2 uses Z39.50 as its switchboard language -- i.e. as far as it
    is concerned, all resources speak Z39.50. It is, however, equipped
    to handle a broad range of different server behavior, through
    configurable query mapping and record normalization. If you develop
    configuration, stylesheets, etc., for a new type of resources, we
    encourage you to share your work. But you can also use pazpar2 to
    connect to hundreds of resources that do not support standard
    protocols.
   </para>

   <para>
    For a growing number of resources, Z39.50 is all you need. Over the
    last few years, a number of commercial, full-text resources have
    implemented Z39.50. These can be used through pazpar2 with little or
    no effort. Resources that use non-standard record formats will
    require a bit of XSLT work, but that's all.
   </para>

   <para>
    But what about resources that don't support Z39.50 at all? The NISO
    SRU (MXG) protocol is slowly gathering steam. Other resources might
    support OpenSearch, private, XML/HTTP-based protocols, or something
    else entirely. Some databases exist only as web user interfaces and
    will require screen-scraping. Still others exist only as static
    files, or perhaps as databases supporting the OAI-PMH protocol.
    There is hope! Read on.
   </para>

   <para>
    Index Data continues to advocate the support of open standards. We
    work with database vendors to support standards, so you don't have
    to worry about programming against non-standard services. We also
    provide tools (see <ulink
     url="http://www.indexdata.com/simpleserver">SimpleServer</ulink>)
    which make it comparatively easy to build gateways against servers
    with non-standard behavior. Again, we encourage you to share any
    work you do in this direction.
   </para>

   <para>
    But the bottom line is that working with non-standard resources in
    metasearching is really, really hard. If you want to build a
    project with pazpar2, and you need access to resources with
    non-standard interfaces, we can help. We run gateways to more than
    2,000 popular, commercial databases and other resources,
    making it simple 
    to plug them directly into pazpar2. For a small annual fee per
    database, we can help you establish connections to your licensed
    resources. Meanwhile, you can help! If you build your own
    standards-compliant gateways, host them for others, or share the
    code! And tell your vendors that they can save everybody money and
    increase the appeal of their resources by supporting standards.
   </para>

   <para>
    There are those who will ask us why we are using Z39.50 as our
    switchboard langyage rather than a different protocol. Basically,
    we believe that Z39.50 is presently the most widely implemented 
    information retrieval protocol that has the level of functionality
    required to support a good metasearching experience (structured
    searching, structured, well-defined results). It is also compact and
    efficient, and there is a very broad range of tools available to
    implement it.
   </para>
  </section>

  <section id="unicode">
   <title>Unicode Compliance</title>
   <para>
    Pazpar2 is unicode compliant and language and locale aware to
    the exted the used backend Z39.50 targets are. Just a few bad
    behaving targets can spoil the search experience considerably
    if for example Greek, Russian or otherwise non 7-bit ASCII
    search terms are entered. In these cases some targets return
    records irrelevant to the query, and the result screens wil be
    cluttered with noise.
   </para>
   <para>
    While noise from misbehaving targets can not be removed, it can
    be reduced using truely unicode based ranking. This is an
    option which is available to the system administrator if ICU
    support is compiled into Pazpar2, see
    <xref linkend="installation"/> for details.
   </para>
   <para>
    In addition, the ICU tokenization and normalization rules must
    be defined in the master configuration file described in 
    <xref linkend="config-server"/>.
   </para>
  </section>

 </chapter> <!-- Using pazpar2 -->

 <reference id="reference">
  <title>Reference</title>
  <partintro id="reference-introduction">
   <para>
    The material in this chapter is drawn directly from the individual
    manual entries.
   </para>
  </partintro>
  &manref;
 </reference>

 <appendix id="license"><title>License</title>
  
  <section id="gpl"><title>GPL</title>
   
   <para>
    Pazpar2,
    Copyright &copy; &copyright-year; Index Data.
   </para>
   
   <para>
    Pazpar2 is free software; you can redistribute it and/or modify it under
    the terms of the GNU General Public License as published by the Free
    Software Foundation; either version 2, or (at your option) any later
    version.
   </para>
   
   <para>
    Pazpar2 is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.
   </para>
   
   <para>
    You should have received a copy of the GNU General Public License
    along with Pazpar2; see the file LICENSE.  If not, write to the
    Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
    02111-1307, USA.
   </para>
   
   <screen>
                    GNU GENERAL PUBLIC LICENSE
                       Version 2, June 1991

 Copyright (C) 1989, 1991 Free Software Foundation, Inc.
     59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

                            Preamble

  The licenses for most software are designed to take away your
freedom to share and change it.  By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users.  This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it.  (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.)  You can apply it to
your programs, too.

  When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it
in new free programs; and that you know you can do these things.

  To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

  For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their
rights.

  We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

  Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

  Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

  The precise terms and conditions for copying, distribution and
modification follow.

                    GNU GENERAL PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
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Activities other than copying, distribution and modification are not
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You may charge a fee for the physical act of transferring a copy, and
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These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.  But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.

In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.

  3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:

    a) Accompany it with the complete corresponding machine-readable
    source code, which must be distributed under the terms of Sections
    1 and 2 above on a medium customarily used for software interchange; or,

    b) Accompany it with a written offer, valid for at least three
    years, to give any third party, for a charge no more than your
    cost of physically performing source distribution, a complete
    machine-readable copy of the corresponding source code, to be
    distributed under the terms of Sections 1 and 2 above on a medium
    customarily used for software interchange; or,

    c) Accompany it with the information you received as to the offer
    to distribute corresponding source code.  (This alternative is
    allowed only for noncommercial distribution and only if you
    received the program in object code or executable form with such
    an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for
making modifications to it.  For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable.  However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.

If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.

  4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.

  5. You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.  These actions are
prohibited by law if you do not accept this License.  Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

  6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions.  You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.

  7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.

It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices.  Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

  8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

  9. The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and "any
later version", you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation.  If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software
Foundation.

  10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission.  For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this.  Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.

                            NO WARRANTY

  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.

  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.

                     END OF TERMS AND CONDITIONS
   </screen> 
  </section>
 </appendix>
 
</book>

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