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new entries; new area of tree devoted to whitepapers, ref material, tutorials, etc...those that are not HOWTOs, FAQs or Guides.

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<!DOCTYPE ARTICLE PUBLIC "-//OASIS//DTD DocBook V4.1//EN" [
<!-- Document version -->
<!ENTITY DOCVERSION "0.1">
<!-- File Includes -->
<!ENTITY GFDL-FILE SYSTEM "gfdl.sgml">
<!-- Text substitution macros -->
<!ENTITY CVS "Concurrent Versions System">
<!ENTITY OPENSOURCE "Open Source">
<!ENTITY CVSAB "CVS">
<!ENTITY SCMAB "SCM">
<!ENTITY SCM "Software configuration management">
<!ENTITY MYEMAIL "vivekv@users.sourceforge.net">
]>
<article>
<title>CVS Best Practices</title>
<articleinfo>
<author>
<firstname>Vivek</firstname>
<surname>Venugopalan</surname>
<affiliation>
<address><email>vivekv@users.sourceforge.net</email></address></affiliation>
</author>
<revhistory>
<revision>
<revnumber>0.1</revnumber>
<date>2001-11-20</date>
<authorinitials>vv</authorinitials>
<revremark>Created</revremark>
</revision>
</revhistory>
</articleinfo>
<abstract>
<indexterm>
<primary>CVS Best Practices</primary>
</indexterm>
<para>This article explores some of the best practices that can be adopted
while using CVS as the configuration management tool in your software
projects.
</para>
</abstract>
<sect1 id="section1-intro">
<title>Introduction</title>
<blockquote>
<attribution>unknown</attribution>
<literallayout>A tool is only as good as you use it
</literallayout>
</blockquote>
<para>This article outlines some of the best practices that can be adopted
when &CVS; is used as the configuration management tool in your software
project. </para>
<para>&CVS; (&CVSAB;) is an <ulink
url="http://www.opensource.org">&OPENSOURCE;</ulink> configuration management
tool that is now being looked at seriously by many commercial organizations as
a viable alternative to other commercial &SCM; tools. </para>
<para>This spotlight on &CVSAB; has led to the inevitable question of best
practices for deploying &CVSAB; as the backbone &SCMAB; tool for large
software development projects. Having answered this question many times
verbally as a bunch of <quote>gotchas</quote> on &CVSAB;, it was time to put
down on paper some of the best practices that I have adopted while managing
&CVSAB; based projects. </para>
<!-- Section2: copyright -->
<sect2 id="copyright">
<title>Copyright Information</title>
<para> This document is Copyright &copy; 2001 Vivek Venugopalan.
Permission is granted to copy, distribute and/or modify this document
under the terms of the <link linkend="gfdl"><citetitle>GNU Free
Documentation License</citetitle></link>, Version 1.1 or any later
version published by the Free Software Foundation with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the
license can be found in <xref linkend="gfdl">.
</para>
<para> This document may be reproduced and distributed in whole or in part,
in any medium physical or electronic, as long as this copyright notice is
retained on all copies. Commercial redistribution is allowed and encouraged;
however, the author would like to be notified of any such distributions.
</para>
<para> All translations, derivative works, or aggregate works incorporating
this document must be covered under this copyright notice. That is, you may
not produce a derivative work from this document and impose additional
restrictions on its distribution. Exceptions to these rules may be granted
under certain conditions; please contact the author at the
address given below. </para>
<para> In short, we wish to promote dissemination of this information through
as many channels as possible. However, we do wish to retain copyright on the
document, and would like to be notified of any plans to redistribute
the same. </para>
<para> If you have any questions, please contact
<email>linux-howto@metalab.unc.edu</email> </para> </sect2>
<!-- Section2: disclaimer -->
<sect2 id="disclaimer"> <title>Disclaimer</title>
<para> No liability for the contents of this document can be accepted. Use
the concepts, examples and other content at your own risk. As this is a new
edition of this document, there may be errors and inaccuracies that may of
course be damaging to your system. Proceed with caution, and although this is
highly unlikely, the author(s) do not take any responsibility for that.
</para>
<para> All copyrights are held by their respective owners, unless
specifically noted otherwise. Use of a term in this document should not be
regarded as affecting the validity of any trademark or service mark. </para>
<para> Naming of particular products or brands should not be seen as
endorsements. </para>
<para> You are strongly recommended to take a backup of your system before
major installation and backups at regular intervals. </para> </sect2>
<!-- Section2: newversions-->
<sect2 id="newversions">
<title>New Versions</title>
<indexterm> <primary></primary> </indexterm>
<para> The version number of this document is &DOCVERSION;. </para>
<para> The latest version of this document can be obtained from <ulink
url="http://www.linuxdoc.org">The linux documentation project</ulink> </para>
</sect2>
<!-- Section2: credits -->
<!-- Nothing yet. Will do so after the first release and the feedback. -->
<!-- Section2: feedback -->
<sect2 id="feedback">
<title>Feedback</title>
<para> Feedback is most certainly welcome for this document. Without your
submissions and input, this document wouldn't exist. Please send your
additions, comments and criticisms to the following email address :
<email>&MYEMAIL;</email>. </para> </sect2>
</sect1>
<sect1 id="section1-focusareas">
<title>Focus Areas</title>
<para>The focus areas for best practice are
</para>
<orderedlist>
<listitem>
<para>GUI Tools
</para>
<itemizedlist>
<listitem>
<para>Use GUI tools for &CVSAB; client
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Developer Sandbox
</para>
<itemizedlist>
<listitem>
<para>Do not share the sandbox
</para>
</listitem>
<listitem>
<para>Do not work outside the sandbox
</para>
</listitem>
<listitem>
<para>Stay in sync with the repository
</para>
</listitem>
<listitem>
<para>Check-in often
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Branching and Merging
</para>
<itemizedlist>
<listitem>
<para>Assign ownership to trunk and branches
</para>
</listitem>
<listitem>
<para>Tag each release
</para>
</listitem>
<listitem>
<para>Create a branch after each release
</para>
</listitem>
<listitem>
<para>Make bug fixes to branches only
</para>
</listitem>
<listitem>
<para>Make patch releases from branches only
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Change propagation
</para>
<itemizedlist>
<listitem>
<para>Merge branch with the trunk after each release
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Software Builds
</para>
<itemizedlist>
<listitem>
<para>Build early and build often
</para>
</listitem>
<listitem>
<para>Automate build process completely
</para>
</listitem>
<listitem>
<para>All necessary files must be checked in before a build
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Institutionalizing and Process
</para>
<itemizedlist>
<listitem>
<para>Implement change management
</para>
</listitem>
<listitem>
<para>Make &CVSAB; usage part of developer's objectives
</para>
</listitem>
<listitem>
<para>Collect metrics on &CVSAB; usage
</para>
</listitem>
</itemizedlist>
</listitem>
</orderedlist>
</sect1>
<!-- Using GUI Tools -->
<sect1 id="section1-guitools">
<title>Using GUI Tools</title>
<para> Developers typically use integrated development environments that have
the CM tools integrated into them. These tools minimize the learning for the
developers about the intricacies of &CVSAB; usage and instead allow them to be
productive from day one. Developers who are accustomed to other CM tools will
find the &CVSAB; command-line interface daunting. The adoption and usage of
&CVSAB; can be improved by using GUI tools for &CVSAB; clients. GUI tools for
&CVSAB; are available at <ulink url="www.cvsgui.org">www.cvsgui.org</ulink>.
GUI interfaces are available for most of the popular platforms (Windows, Mac
and Linux). In addition, on the Windows platform there is a SCC extension
that allows integration of &CVSAB; as the configuration control tool with
popular IDE.</para>
</sect1>
<sect1 id="section1-devsandbox">
<title>Developer Sandbox</title>
<para>The developer <quote>sandbox</quote> is where each developer keeps his
or her working copy of the code base. This is where they build, test and
debug the modules that they are working on. A sandbox can also be the area
where the staging build or the production build is done. Changes made in
the work area are checked into the &CVSAB; repository. In addition, changes
made in the repository by others have to be updated in the sandbox on a
regular basis. </para>
<para>The best practices related to developers sandbox are:
</para>
<sect2 id="section2-dontshare">
<title>Do not share the sandbox</title>
<para>Sandboxes have to be unique for each developer or purpose. They should
not be used for multiple things at the same time. A sandbox can be a working
area for a developer or the build area for the final release. If such
workspaces are shared, then the developers themselves will not be aware of the
changes made to the files resulting in confusion. </para>
<para>In &CVSAB;, the sandbox is created automatically when a working copy is
checked out for a &CVSAB; project using the <command>cvs checkout
{project-name}</command> command. </para>
</sect2>
<sect2 id="section2-workinside">
<title>Do not work outside the sandbox</title>
<para>The sandbox can be thought of as a controlled area within which
&CVSAB; can track for changes made to the various source files. Files
belonging to other developers can be automatically updated by &CVSAB;. Thus
the developer who lives within the sandbox will stand to gain a lot of
benefits of concurrent development that cannot be done if work is done
outside a sandbox. </para> </sect2>
<sect2 id="section2-syncup">
<title>Stay in Sync with the repository</title>
<para>To gain the benefits of working within a sandbox as mentioned above,
the developer must keep his or her workspace in sync with the main
repository. A regular <command>cvs update</command> with the appropriate
tag will ensure that the sandboxes are kept up to date. </para> </sect2>
<sect2 id="section2-checkin">
<title>Check-in Often</title>
<para>To help other developers keep their code in sync with your code, you
must check-in your code often into the &CVSAB; repository. As soon as a
piece of code is completed and tested, check-in the changes using a
<command>cvs commit</command> to ensure that your changes are committed to
the &CVSAB; repository. </para>
</sect2>
</sect1>
<sect1 id="section1-branchmerge">
<title>Branching and Merging</title>
<para> Branching in &CVSAB; splits a project's development into separate,
parallel histories. Changes made on one branch do not affect the other
branches. Branching can be used extensively to maintain multiple versions
of a product for providing support and new features. </para>
<para> Merging converges the branches back to the main trunk. In a merge,
CVS calculates the changes made on the branch between the point where it
diverged from the trunk and the branch's tip (its most recent state), then
applies those differences to the project at the tip of the trunk. </para>
<sect2 id="section2-branchowner">
<title>Assign Ownership to Trunk and Branches</title>
<para>The main trunk of the source tree and the various branches should have a
owner assigned who will be responsible for. </para>
<orderedlist>
<listitem>
<para>Establish a working policy for the branch or trunk.
</para>
<para>The owner will establish policies for check-in and check-out. The
policy will define when the code can be checked in (after coding or after
review etc.,). Who is responsible to merge changes on the same file and
resolve conflicts (the author or the person who recently changed the file).
</para>
</listitem>
<listitem>
<para>Identify and document policy deviations
</para>
<para>Policies once established tend to have exceptions. The owner will be
responsible for identifying the workaround and tracking/documenting the same
for future use. </para>
</listitem>
<listitem>
<para>Responsible for merge with the trunk
</para>
<para>The branch owner will be responsible for ensuring that the changes in
the branch can be successfully merged with the main trunk at a reasonable point
in time. </para>
</listitem>
</orderedlist>
</sect2>
<sect2 id="section2-tagrelease"> <title>Tag each release</title> <para>After
each release, the entire code base must be tagged with an identifier that
can help in uniquely identifying the release. A tag gives a label to the
collection of revisions represented by one developer's working copy
(usually, that working copy is completely up to date so the tag name is
attached to the <quote>latest and greatest</quote> revisions in the
repository). </para>
<para>The identifier for the tag should provide enough information to
identify the release at any point in time in the future. One suggested tag
identifier is of the form. </para>
<literallayout>
<literal>release_</literal>{major version #}_{minor version #}
</literallayout>
</sect2>
<sect2 id="section2-branchatrelease">
<title>Create a branch after each release</title>
<para>After each software release, once the &CVSAB; repository is tagged, a
branch has to be immediately created. This branch will serve as the bug fix
branch for that release. This branch is created only if the release is not
a bug fix or patch release. Patches that have to be made for this release
at any point in time in the future will be developed on this branch. The
main trunk will be used for ongoing product development. </para>
<para>With this arrangement, the changes in the code for the ongoing
development will be on the main trunk and the branch will provide a separate
partition for hot fixes and bug fix releases. </para>
<para>The identifier for the branch name can be of the form. </para>
<literallayout>
<literal>release_</literal>{major version #}_{minor version #}<literal>_patches</literal>
</literallayout>
</sect2>
<sect2 id="section2-bugfixbranches">
<title>Make bug fixes to branches only</title>
<para>This practice extends from the previous practice of creating a
separate branch after a major release. The branch will serve as the code
base for all bug fixes and patch release that have to be made. Thus, there
is a separate repository <quote>sandbox</quote> where the hot fixes and
patches can be developed apart from the mainstream development. </para>
<para>This practice also ensures that bug fixes done to previous releases do
not mysteriously affect the mainstream version. In addition, new features
added to the mainstream version do not creep into the patch release
accidentally. </para>
</sect2>
<sect2 id="section2-patchesfrombranches">
<title>Make patch release from branches only</title>
<para>Since all the bug fixes for a given release are done on its
corresponding branch, the patch releases are made from the branch. This
ensures that there is no confusion on the feature set that is released as
part of the patch release. </para>
<para>After the patch release is made, the branch has to be tagged using the
release tagging practice (see <xref linkend="section2-tagrelease">). </para>
</sect2>
</sect1>
<sect1 id="section1-chgpropagation">
<title>Change Propagation</title>
<para>Change propagation practices explores how changes made to one version of
the application are migrated to other living versions of the application.
</para>
<sect2 id="section2-mergebugfix">
<title>Merge branch with the trunk after release</title>
<para>After each release from a branch, the changes made to the branch should
be merged with the trunk. This ensures that all the bug fixes made to the
patch release are properly incorporated into future releases of the
application. </para>
<para>This merge could potentially be time consuming depending on the amount
of changes made to the trunk and the branch being merged. In fact, it will
probably result in a lot of conflicts in &CVSAB; resulting in manual merges.
After the merge, the trunk code base must be tested to verify that the
application is in proper working order. This must be kept in mind while
preparing the project schedule. </para>
</sect2>
</sect1>
<sect1 id="section1-softwarebuild">
<title>Software Builds</title>
<para>This section deals with the best practices for software builds. Build
is the process of creating the application binaries for a software release.
They are done in a periodic manner in development teams to provide baseline
binaries for daily work. </para>
<sect2 id="section2-bebo">
<title>Build Early and Build Often (<acronym>BEBO</acronym>) </title>
<para>A slight variation of this adage has been around in the &OPENSOURCE;
community called "Release Early and Release Often" for quite some time albeit
for a different reason. BEBO helps a development team identify issues that
can arise from checking in the wrong files. BEBO will address
integration issues at the application level that might have slipped
passed individual developer builds. It will also improve the team morale when
they see a working version of the application.</para>
<para>Builds must be done on a regular basis. There should be a dedicated
resource(s) assigned to do the same. The entire project team must be trained
to view the daily build as an important activity and not as a chore. Builds
must be completed without any failures on a regular basis. Build failures
must be a rare event and should be treated with utmost seriousness. The
project team should ensure that successful builds are top priority on their
agenda. The seriousness can be emphasised by setting up a penalty for
breaking the build. </para>
</sect2>
<sect2 id="section2-automate">
<title>Automate Build Process completely</title>
<para>Another key practice for software builds is to automate the build
process completely. The automation process must also include automatic
retrieval of the right source files from the &CVSAB; repository. This
ensures that the build process is completely repeatable and consistent. In
addition, the chances of a build with the wrong version of the application
source files are reduced to a large degree. </para>
</sect2>
<sect2 id="section2-ensurecheckin">
<title>All necessary files must be checked before build</title>
<para>This adage sounds trivial at first but this problem is very common
even with experienced development teams due to oversight. The problem of
oversight cannot be easily addressed since the onus is on the individual
developer to ensure that his or her file has been checked in. This practice
should be drummed into the team in the form of trainings and pre-build
announcements to ensure that the right version of source code is available
in the repository. </para>
<para>Automated build process as explained above will help in catching this
problem to a certain degree since they will automatically take the source code
from the &CVSAB; repository and perform the software build. Any missed items
will surface during the build process itself (makefiles etc.,) or during the
regression testing of the product (older version of the file checked in).
</para>
</sect2>
</sect1>
<sect1 id="section1-instprocess">
<title>Institutionalize &CVSAB; in the Organization</title>
<para>Here we will look at the best practices for institutionalizing &CVSAB;
usage in the organization.
</para>
<sect2 id="section2-chngmgmt">
<title>Implement Change Management Process</title>
<para>All organizations must implement a good Change management process
(<acronym>CMP</acronym>). A good CMP will define how changes are received and
recorded, tracked, executed and delivered. &CVSAB; provides version control
for your project. Change management addresses the <quote>bigger
picture</quote> of how enhancements and bugs are received, tracked and
closed. &CVSAB; will play a smaller but a very important part in this
entire picture. With a formal change management process in place in
the organization, tools such as &CVSAB; will be looked at as aiding
this process instead of acting as a general development overhead.
</para>
</sect2>
<sect2 id="section2-objectives">
<title>Make &CVSAB; Usage part of Objectives</title>
<para>To institutionalize &CVSAB;, it can be made as part of the annual
objectives for the developer to use it as part of his or her project. In addition,
it can also be made as part of the objective for the project manager to deploy
&CVSAB; in his or her project. </para>
<para>Compliance of this can then be reviewed as part of the appraisal cycle
for the employee. </para>
</sect2>
<sect2 id="section2-metrics">
<title>Collect metrics on &CVSAB; usage</title>
<para>&CVSAB; usage metrics can be collected in terms of percentage of
deployment in the organization, project size handled etc., This information
will spur other line managers and program managers to look at &CVSAB; as a
tool that will aid them in their daily operations.
</para>
</sect2>
</sect1>
<sect1 id="section1-conclusion">
<title>Conclusion</title>
<para>These best practices are meant to help software teams get a head start
on using &CVSAB; for their development. The ideas presented here have to be
constantly reviewed and evolved. I would like this to be a growing and
evolving document. Please send your comments and ideas to
<email>&MYEMAIL;</email> </para>
</sect1>
<!-- Include the GNU FDL -->
&GFDL-FILE;
</article>

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<appendix id="gfdl">
<title>GNU Free Documentation License</title>
<!-- - GNU Project - Free Software Foundation (FSF) -->
<!-- LINK REV="made" HREF="mailto:webmasters@gnu.org" -->
<!-- sect1>
<title>GNU Free Documentation License</title -->
<para>Version 1.1, March 2000</para>
<blockquote>
<para>Copyright (C) 2000 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.</para>
</blockquote>
<sect1 label="0">
<title>Preamble</title>
<para>The purpose of this License is to make a manual, textbook,
or other written document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by
others.</para>
<para>This License is a kind of "copyleft", which means that
derivative works of the document must themselves be free in the
same sense. It complements the GNU General Public License, which
is a copyleft license designed for free software.</para>
<para>We have designed this License in order to use it for manuals
for free software, because free software needs free documentation:
a free program should come with manuals providing the same
freedoms that the software does. But this License is not limited
to software manuals; it can be used for any textual work,
regardless of subject matter or whether it is published as a
printed book. We recommend this License principally for works
whose purpose is instruction or reference.</para>
</sect1>
<sect1 label="1">
<title>Applicability and Definitions</title>
<para>This License applies to any manual or other work that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. The "Document",
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<para>A "Modified Version" of the Document means any work
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<para>A "Secondary Section" is a named appendix or a front-matter
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Opaque formats include PostScript, PDF, proprietary formats that
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</sect1>
<sect1 label="2">
<title>Verbatim Copying</title>
<para>You may copy and distribute the Document in any medium,
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License applies to the Document are reproduced in all copies, and
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<para>You may also lend copies, under the same conditions stated
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</sect1>
<sect1 label="3">
<title>Copying in Quantity</title>
<para>If you publish printed copies of the Document numbering more
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<para>If the required texts for either cover are too voluminous to
fit legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
adjacent pages.</para>
<para>If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a publicly-accessible
computer-network location containing a complete Transparent copy
of the Document, free of added material, which the general
network-using public has access to download anonymously at no
charge using public-standard network protocols. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.</para>
<para>It is requested, but not required, that you contact the
authors of the Document well before redistributing any large
number of copies, to give them a chance to provide you with an
updated version of the Document.</para>
</sect1>
<sect1 label="4">
<title>Modifications</title>
<para>You may copy and distribute a Modified Version of the
Document under the conditions of sections 2 and 3 above, provided
that you release the Modified Version under precisely this
License, with the Modified Version filling the role of the
Document, thus licensing distribution and modification of the
Modified Version to whoever possesses a copy of it. In addition,
you must do these things in the Modified Version:</para>
<orderedlist numeration="upperalpha">
<listitem><para>Use in the Title Page
(and on the covers, if any) a title distinct from that of the
Document, and from those of previous versions (which should, if
there were any, be listed in the History section of the
Document). You may use the same title as a previous version if
the original publisher of that version gives permission.</para>
</listitem>
<listitem><para>List on the Title Page,
as authors, one or more persons or entities responsible for
authorship of the modifications in the Modified Version,
together with at least five of the principal authors of the
Document (all of its principal authors, if it has less than
five).</para>
</listitem>
<listitem><para>State on the Title page
the name of the publisher of the Modified Version, as the
publisher.</para>
</listitem>
<listitem><para>Preserve all the
copyright notices of the Document.</para>
</listitem>
<listitem><para>Add an appropriate
copyright notice for your modifications adjacent to the other
copyright notices.</para>
</listitem>
<listitem><para>Include, immediately
after the copyright notices, a license notice giving the public
permission to use the Modified Version under the terms of this
License, in the form shown in the Addendum below.</para>
</listitem>
<listitem><para>Preserve in that license
notice the full lists of Invariant Sections and required Cover
Texts given in the Document's license notice.</para>
</listitem>
<listitem><para>Include an unaltered
copy of this License.</para>
</listitem>
<listitem><para>Preserve the section
entitled "History", and its title, and add to it an item stating
at least the title, year, new authors, and publisher of the
Modified Version as given on the Title Page. If there is no
section entitled "History" in the Document, create one stating
the title, year, authors, and publisher of the Document as given
on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.</para>
</listitem>
<listitem><para>Preserve the network
location, if any, given in the Document for public access to a
Transparent copy of the Document, and likewise the network
locations given in the Document for previous versions it was
based on. These may be placed in the "History" section. You
may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.</para>
</listitem>
<listitem><para>In any section entitled
"Acknowledgements" or "Dedications", preserve the section's
title, and preserve in the section all the substance and tone of
each of the contributor acknowledgements and/or dedications
given therein.</para>
</listitem>
<listitem><para>Preserve all the
Invariant Sections of the Document, unaltered in their text and
in their titles. Section numbers or the equivalent are not
considered part of the section titles.</para>
</listitem>
<listitem><para>Delete any section
entitled "Endorsements". Such a section may not be included in
the Modified Version.</para>
</listitem>
<listitem><para>Do not retitle any
existing section as "Endorsements" or to conflict in title with
any Invariant Section.</para>
</listitem>
</orderedlist>
<para>If the Modified Version includes new front-matter sections
or appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.</para>
<para>You may add a section entitled "Endorsements", provided it
contains nothing but endorsements of your Modified Version by
various parties--for example, statements of peer review or that
the text has been approved by an organization as the authoritative
definition of a standard.</para>
<para>You may add a passage of up to five words as a Front-Cover
Text, and a passage of up to 25 words as a Back-Cover Text, to the
end of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.</para>
<para>The author(s) and publisher(s) of the Document do not by
this License give permission to use their names for publicity for
or to assert or imply endorsement of any Modified Version.</para>
</sect1>
<sect1 label="5">
<title>Combining Documents</title>
<para>You may combine the Document with other documents released
under this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice.</para>
<para>The combined work need only contain one copy of this
License, and multiple identical Invariant Sections may be replaced
with a single copy. If there are multiple Invariant Sections with
the same name but different contents, make the title of each such
section unique by adding at the end of it, in parentheses, the
name of the original author or publisher of that section if known,
or else a unique number. Make the same adjustment to the section
titles in the list of Invariant Sections in the license notice of
the combined work.</para>
<para>In the combination, you must combine any sections entitled
"History" in the various original documents, forming one section
entitled "History"; likewise combine any sections entitled
"Acknowledgements", and any sections entitled "Dedications". You
must delete all sections entitled "Endorsements."</para>
</sect1>
<sect1 label="6">
<title>Collections of Documents</title>
<para>You may make a collection consisting of the Document and
other documents released under this License, and replace the
individual copies of this License in the various documents with a
single copy that is included in the collection, provided that you
follow the rules of this License for verbatim copying of each of
the documents in all other respects.</para>
<para>You may extract a single document from such a collection,
and distribute it individually under this License, provided you
insert a copy of this License into the extracted document, and
follow this License in all other respects regarding verbatim
copying of that document.</para>
</sect1>
<sect1 label="7">
<title>Aggregation with Independent Works</title>
<para>A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, does not as a whole count as a
Modified Version of the Document, provided no compilation
copyright is claimed for the compilation. Such a compilation is
called an "aggregate", and this License does not apply to the
other self-contained works thus compiled with the Document, on
account of their being thus compiled, if they are not themselves
derivative works of the Document.</para>
<para>If the Cover Text requirement of section 3 is applicable to
these copies of the Document, then if the Document is less than
one quarter of the entire aggregate, the Document's Cover Texts
may be placed on covers that surround only the Document within the
aggregate. Otherwise they must appear on covers around the whole
aggregate.</para>
</sect1>
<sect1 label="8">
<title>Translation</title>
<para>Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires
special permission from their copyright holders, but you may
include translations of some or all Invariant Sections in addition
to the original versions of these Invariant Sections. You may
include a translation of this License provided that you also
include the original English version of this License. In case of
a disagreement between the translation and the original English
version of this License, the original English version will
prevail.</para>
</sect1>
<sect1 label="9">
<title>Termination</title>
<para>You may not copy, modify, sublicense, or distribute the
Document except as expressly provided for under this License. Any
other attempt to copy, modify, sublicense or distribute the
Document 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.</para>
</sect1>
<sect1 label="10">
<title>Future Revisions of this License</title>
<para>The Free Software Foundation may publish new, revised
versions of the GNU Free Documentation 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. See <ulink
url="http://www.gnu.org/copyleft/">http://www.gnu.org/copyleft/</ulink>.</para>
<para>Each version of the License is given a distinguishing
version number. If the Document specifies that a particular
numbered version of this License "or any later version" applies to
it, you have the option of following the terms and conditions
either of that specified version or of any later version that has
been published (not as a draft) by the Free Software Foundation.
If the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation.</para>
</sect1>
<sect1 label="">
<title>How to use this License for your documents</title>
<para>To use this License in a document you have written, include
a copy of the License in the document and put the following
copyright and license notices just after the title page:</para>
<blockquote><para>
Copyright (c) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with the Invariant Sections being LIST THEIR TITLES, with the
Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
A copy of the license is included in the section entitled "GNU
Free Documentation License".
</para></blockquote>
<para>If you have no Invariant Sections, write "with no Invariant
Sections" instead of saying which ones are invariant. If you have
no Front-Cover Texts, write "no Front-Cover Texts" instead of
"Front-Cover Texts being LIST"; likewise for Back-Cover
Texts.</para>
<para>If your document contains nontrivial examples of program
code, we recommend releasing these examples in parallel under your
choice of free software license, such as the GNU General Public
License, to permit their use in free software.</para>
</sect1>
</appendix>