Documentation for the Realtime Diagnostics System 1.0.0

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Introduction to the RTS

This manual describes how to use the Realtime Diagnostics System (version 1.0.0), a meteorological diagnostics and display application.

Copyright © 2001, 2003 Free Software Foundation, Inc.

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 no Invariant Sections, with the Front-Cover texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License” in the Emacs manual.

(a) The FSF's Back-Cover Text is: “You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.”

This document is part of a collection distributed under the GNU Free Documentation License. If you want to distribute this document separately from the collection, you can do so by adding a copy of the license to the document, as described in section 6 of the license.

The RealTime diagnostics and display System (RTS) facilitates the compuatation and plotting of advanced meteorological diagnostics in a real-time environment. The RTS relies on well-established libraries for most of its computations, essentially representing an easily-modifiable front-end inteface for computation and display.


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1 Overview

The RealTime diagnostics and display System (RTS) was originally developed at the University at Albany / State University of New York (SUNY), starting in 2004. The intention of the RTS is to generate high resolution, high quality plots of advanced diagnostic variables in real-time. Moreover, the RTS is designed to archive the generated images over a long period of time and provide an easy-to-use web based interface for access to - and animation of - long periods of image data.

As noted in the licencing and copying agreement (see Copying Conditions) we encourage all users of this software to become developers and to contribute to the evolution of the RTS. Please share any developments or enhancements that you add to the system so that others may benefit from your efforts.


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1.1 RTS Components

The RTS is a collection of programs and scripts that compute advanced diagnostics, plot the resulting fields, handle the image data and allow users to quickly access long time-series loops through a web interface. The languages used in the development of the RTS include FORTRAN90, Korn Shell, HTML, PHP, Perl and Python. Although a high level of familiarity with each of these languages is not required for the basic installation and running of the RTS, modifications to the components of the RTS may require some level of proficiency in them.

`generateTropPlots.sh'
This Korn Shell script forms the basis of the automated features of the RTS. It resides in the realtimeSystem/automation folder and directs the generation and image manipulation processes. Modifications to this script may be necessary if the system configurations have changed since the package was installed or if a customized level of service is required. This script may be executed as a cron job with short repeat intervals (5 minutes is used at the University at Albany) to check for the completion of dataset decoding by the LDM.
`mapping.f90'
This FORTRAN90 source code is the workhorse of the RTS and handles all data I/O and processing, and image generation. It resides in the realtimeSystem/mapping_f90 folder and can be compiled to produce the mapping executable. Modifications to this file are required if any of the diagnostics are to be changed or updated.
`mapping'
This executable is generated when the RTS package is built and is installed into the realtimeSystem/mapping_f90 folder. It is executed by the generateTropPlots.sh script and must be regenerated each time that the mapping.f90 source code is modified.
`settings.cfg'
This plain-text settings file is not included with the RTS distribution; instead, it is generated each time that the generateTropPlots.sh script detects a newly-decoded data file. File path and type information is written automatically to this file.
`config'
This folder contains plotting-specific configurations for the mapping executable. It resides in the realtimeSystem/mapping_f90 folder and contains a number of easily-identifiable configuration files. These files may be changed withough recompiling the mapping executable.
`realtimeupdate.py'
This Python program generates and updates the web-based user interface. It is contained in the HTDOCS folder, where HTDOCS is defined at the configuration-time of the package. No modifications should be required to this file unless extensive changes are made to the structure or functionality of the RTS.
`dtmaps.cgi-tmpl'
This Perl Common Gateway Interface (CGI) script template is used to create dtmaps.cgi, the Perl script that handles the extraction of images requested by a user on the web-based interface. It resides in the HTDOCS/cgi-bin folder, where HTDOCS is defined at the configuation-time of the package. There should be no need for modifications to the template, but inline documentation describes the functionality of the CGI script.
`animSelect.php-tmpl'
This HTML document template is used to create animSelect.php, the web-based user interface for the RTS. It resides in the HTDOCS/DTmaps folder, where HTDOCS is defined at the configuation-time of the package. There should be no need to modify this template unless extensive changes are made to the RTS.
`animSelect.cfg'
This plain-text configuration file allows for a great level of flexibility in the interface by providing a stand-alone set of configurations that are used in the generation of the dtmaps.cgi and animSelect.php interface files from the templates described above. The realtimeupdate.py program processes this configuration file whenever it is executed, generating new interface files from the templates. This file must be modified every time that new fields, domains, levels or time increments are added to the RTS.


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1.2 RTS Dependencies

The RTS depends on a number of libraries for computation and plotting processes. In addition, some non-standard applications are required for the complete processing of the resulting data.

The MetCal/SPA package is a basic requirement for the RTS. This package is available from SourceForge and should be installed and configured for any system on which the RTS is to be built. The MetCal/SPA libraries provide the bulk of the RTS functionality.

The NCAR Graphics package is also required for the RTS. This package is available from UCAR and should be installed and configured before the RTS system is built. Although the MetCal/SPA package is designed to be compiled with or without NCAR Graphics installed, an NCAR Graphics enabled version of the MetCal/SPA is required for RTS functionality. This package should therefore be configured and installed before MetCal/SPA.

The NCAR Spherepack package is required for the highly-accurate global spherical calculations employed by the RTS. Although not a strict requirement, since the RTS will also run without spherical computations, both computational time and accuracy are enhanced if the NCAR Spherepack package (available at SpherePack) is configured and installed before MetCal/SPA or the RTS is built. Notes on the installation of Spherepack are available at SpherePack.

The poster utility is required for the generation and printing of 11x17 size Special Services plots. As of RTS version 1.0.0, polar stereographic dynamic tropopause maps are generated and printed using this utility. The poster program is available at The FSF.


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2 Running the RealTime System

This chapter describes how to configure, install and run the RTS in both interactive and batch mode. Please note that the packages on which the SPA depends (see for a description of dependencies) should be installed and configured before this installation of the RTS is begun.


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2.1 Installation of the RTS

Once all of the packages on which the RTS depends have been configured and installed (see for a description of dependencies), the RTS package itself can be configured. The RTS uses GNU autotools to ensure platform-independence and to ease the setup and installation process. An example of the commands issued to configure, build an install the RTS is:

     ./configure --prefix=/path/to/install \
       HTDOCS=/path/to/web/document/directory
     make all >&make.out
     make install >&install.out

The configure script included with the RTS distribution usually does a good job of determining the setup of your machine. Be sure to watch for warnings as the configuration progresses, since not all problems are fatal, but they may impact the performance of the RTS. Additional settings can be made by the user at configure time. For a full list of the configurable settings, type:

./configure --help

Potentially useful configurable options include:

`--prefix=/path/to/install'
This option allows the user to set the path into which the computational section of the RTS is installed (i.e. the realtimeSystem directory and its subdirectories). The default for this option is /usr/local.
`HTDOCS=/path/to/web/document/directory'
This option allows the user to set the path into which the web-based portion of the RTS is installed (i.e. the cgi-bin and DTmaps folders). The location pointed to by this path should be visible by your web server, or should be linkable to a directory visible by the web server (any linking will need to be done manually). The default for this option is /usr/local/etc.
`SSDIR=/path/to/special/services/directory'
This option allows the user to set the path in which the Special Services output of the RTS is stored. These are usually images that are of particular interest for a limited amount of time or designed for a special purpose. The default for this option is HTDOCS.
`WORKFILE=/name/of/LDM/decoder/output'
This option allows the user to set the absolute path and name of the output file generated by the LDM decoders as they convert grib data to GEMPAK format. This value will almost certainly vary depending on your local system. All that the decoder output (to the file named here) has to contain once it has finished processing the GEMPAK file is the word Finished (capitalization is important) and long listing (ls -l) of the decoded file. The default for this option is /unidata/products/workdir/gfs255/gfs255.out.
`SERVER=serverName'
If the data decoding and image storage services are not being run on the local machine (this should be considered unusual) then a remote server name can be entered using this option. The default value for this option is the local machine name.


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2.2 Running the RTS interactively

The interactive running mode of the RTS is the simplest way to run the system; however, it is also less powerful than the automated mode described in the next section. The first step in running interactively is to create the settings file settings.cfg in the compuation and image generation directory /path/to/install/realtimeSystem/mapping_f90, where /path/to/install is described in the installation section above. Initially, this directory contains only the mapping.f90 source, the mapping executable and the config subdirectory. The settings.cfg file can be created manually:

'type' 'gem'
'input file information' 'list',1
                        '/data/file/path/and/name'
'output file information' 0
'grid file information' ''

In this example, the /data/file/path/and/name should be replaced by the absolute path to the data file to be processed. Once this file has been produced, simply run the mapping executable to generate the RTS images for the given analysis. The images will be created in the local directory and will remain there once the mapping program terminates.


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2.3 Running the RTS in automated mode

The automated mode of the RTS is the standard format in which to run the system. The generateTropPlots.sh Korn Shell script (residing in the /path/to/install/realtimeSystem/automation folder, where /path/to/install is described in the installation section above) controls the execution of the mapping program in this mode and also separates the output images into formats that can be used directly by the web interface. Although every attempt has been made to keep the RTS as user-configurable as possible, it is possible (and perhaps even likely) that the generateTropPlots.sh script will need to be modified before the system will run flawlessly in automated mode on a given system.

As a first step, the user should try running ./generateTropPlots.sh from the command line in the /path/to/install/realtimeSystem/automation directory (since this directory itself is likely not in the path). If the system produces output beginning with generateTropPlots log, then the automated system has initialized the mapping executable correctly. If no such output appears, then the third line of the generateTropPlots.sh script should be changed to read:

debug=1

This will run the script in debugging mode and allow the user to make any required modifications.

Once the generateTropPlots.sh launch script is running, it will appear to hang as the mapping executable goes through the compuation and plotting process. Note that this execution can take up to 2 hours on a Linux box for high resolution images. This explains why the debugging mode can come in handy while the system is being established. After the plots are generated, generateTropPlots.sh takes over to convert the resulting images to a web-ready format and to transfer them to appropriate archive subdirectories. This image processing can take another 1.5 to 2 hours on a Linux machine for high resolution grids. The images are transferred to the /path/to/web/document/directory/DTmaps/realtime subdirectires that are named according to the image produced. Images accumulate in these archive directories ad infinitum (or at least until the disk space runs out).

The RTS can be run in a fully-automated format by combinging the automatic mode RTS functionality with Unix/Linux cron. Adding a job to the user crontable will use generateTropPlots.sh to create and event handler that detects the completion of LDM data decoding if the RTS is properly configured.

0,10,20,30,40,50 * * * * /path/to/install/realtimeSystem/automation/generateTropPlots.sh \
  >/tmp/log-out 2>/tmp/log-err || cat /tmp/log-err

This line added to the crontable (with the /path/to/install changed as noted in the installation section) will result in an RTS event handler that checks every 10 minutes for decoding completion. Once a new data file is decoded, generateTropPlots.sh writes a new settings.cfg configuration file for the mapping executable and begins to process the data. This is the standard running mode for the RTS.


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3 Modifying the RealTime System

The two primary components of the RTS are the compuational/plotting segement (found in the /path/to/install/realtimeSystem folder, see for a description of installation paths) and the web interface segement (found in the /path/to/web/document/directory folder, see for a description of installation paths). Modifications to either or both of these may be desirable or required.


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3.1 Modifying the Caluclation and Plotting RTS Components

The computational and plotting components of the RTS are located in the /path/to/install/realtimeSystem folder (see for a description of installation paths).

The first modifications made to the RTS will likely be necessary ones made to the automated launch script generateTropPlots.sh. Despite proper configuration, it is possible (and even likely) that the user will have to modify this launch script to get the RTS running in automated mode (see for a description of running the RTS in automated mode). The generateTropPlots.sh script has a debugging flag near the top of the file to assist in the modification process. It is most likely path names and utility references that will need to be changed in the initial modifications. Once the RTS is running in automated mode, very few changes should need to be made to the generateTropPlots.sh file. Even if new plots are added, no changes to the launch script are required.

Once the RTS is running in both interactive and automated modes (see for a description of running modes), additional plots can be added (or existing plots taken away) and other compuatational or plotting changes can be made by modifying the mapping.f90 source code. Familiarity with both FORTRAN90 and the MetCal/SPA package will greatly assist in modifications to this component of the RTS. To recompile the mapping executable, the MetCal command sequence should be run in the mapping_f90 subdirectory.

comp90.d
make mapping

This will build a system-dependent makefile and create the mapping executable. Note that other MetCal utilities can be used to provide further flexibility in terms of modifications to the computational subprograms called by mapping.

Modifications to these two files (generateTropPlots.sh and mapping.f90) should permit for the customization of the compuataional and plotting component of the RTS.


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3.2 Modifying the Web Interace RTS Components

The web interface component of the RTS is located in the /path/to/web/document/directory folder (see for a description of installation paths).

Few initial modifications should be required to the web interface, providing that the HTDOCS option was properly set at configuration time. Common post-installation modifications are accomplished using the animSelect.cfg configuration file. The configuration file is divided into sections using #text# identifiers, where text is one of PATH, FIELD, LEVEL, REGION, INCREMENT, QUALITY, or SIZE. The options provided to users of the web interface are all set in this configuration file. For example, to add a new region (call it 'Asia' for example), an entry in the #REGION# section would have to be added:

region_asia => 'Asia'

The naming of all values in animSelect.cfg is important since the CGI script (dyntrop.cgi) relies on them to find the correct archive subdirectory. In this case, a new domain called asia would have to have been added to the mapping.f90 source (see for a description of modifications to the main RTS program). The string value on the right hand side of the region identifier in this example is completely arbitrary; however, the _asia extension on the region string on the left hand side must match with the changes to the mapping.f90 code. Similarly, a new 2D field can be added (call it 'MG Field of Doom') by inserting a new entry below the #FIELD# header:

field_FoD => 'MG Field of Doom'
levelling_FoD => '2D'
extensions_FoD => '.jpg'
titles_FoD => 'DTmaps/titles/FoDTitle.html'
headers_FoD => 'DTmaps/headers/FoDHead.html'
captions_FoD => 'DTmaps/captions/FoDCap.html'

This is a little more complicated than the previous example, but follows similar lines. On the first line, the field is given an output name ('MG Field of Doom'). This name is completely arbitray; however, the _FoD extension on the field string means that the name of the files generated by mapping are FoD. If this is confusing, try running the mapping executable interactively and watching as the image files are generated. The names of the image files match with one of the sets of field specifications under the #FIELD# header of the animSelect.cfg file. The second line indicates that the field is only two dimensional. In fact, the only important value here is 3D - all other values (for example, 2D, tropopause or Bob) are handled identically as 2D fields. The titles, header and captions strings identify the HTML snippets that are concatenated into the animation web page as it is generated. If these files do not exist, default strings appear. In the case of the example, these files should be generated manually in the folder referred to in animSelect.cfg.

Modifications for the other headings are similar (and generally simpler). Once a modification to the configuration file (animSelect.cfg) is complete, the web interface must be rebuilt with the new information. This is accomplished by running the realtimeupdate.py program (located in the /path/to/web/document/directory directory). This program can be run in the Python shell for full functionality, or can be executed as:

python realtimeupdate.py

The template files (dyntrop.cgi-tmpl and animSelect.php-tmpl) are processed to create the web interface. Although the current version of the interface can be backed up using the Python shell, all changes to dyntrop.cgi and animSelect.php are ephemeral and are replaced once realtimeupdate.py is run. It is thus very important to remember that any changes to the web interface should be made in the template files rather than in the interface files themselves. Following any change to the templates, simply run realtimeupdate.py to generate a new web interface.


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Appendix A Copying Conditions


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A.1 GNU Free Documentation License

Version 1.2, November 2002
     Copyright © 2000,2001,2002 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.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful 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.

    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.

    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.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ascii without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    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.

    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 computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. 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.

    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.

  5. MODIFICATIONS

    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:

    1. 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.
    2. 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 fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. 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.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve 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.
    10. 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.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. 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.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    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.

    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.

    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.

    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.

  6. COMBINING DOCUMENTS

    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, and that you preserve all their Warranty Disclaimers.

    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.

    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.”

  7. COLLECTIONS OF DOCUMENTS

    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.

    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.

  8. AGGREGATION WITH INDEPENDENT WORKS

    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, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    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, and all the license notices in the Document, and any Warrany Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    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.

  11. FUTURE REVISIONS OF THIS LICENSE

    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 http://www.gnu.org/copyleft/.

    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.

A.1.1 ADDENDUM: How to use this License for your documents

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:

       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 1.2
       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 is included in the section entitled
       ``GNU Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

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.


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