Difference: TWikiPlugins (32 vs. 33)

Revision 3316 May 2007 - TWikiContributor

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TWiki Plugins

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TWiki Plugins

  Add functionality to TWiki with readily available Plugins; create Plugins based on APIs
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Overview

You can add Plugins to extend TWiki functionality, without altering the core code. A plug-in approach lets you:

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On-Site Pretesting

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The recommended approach to testing new Plugins before making them public is to create a second local TWiki installation, and test the Plugin there. You can allow selected users access to the test area. Once you are satisifed that it won't compromise your main installation, you can install it there as well.
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The recommended approach to testing new Plugins before making them public is to create a second local TWiki installation, and test the Plugin there. You can allow selected users access to the test area. Once you are satisfied that it won't compromise your main installation, you can install it there as well.
  InstalledPlugins shows which Plugins are: 1) installed, 2) loading properly, and 3) what TWiki:Codev.PluginHandlers they invoke. Any failures are shown in the Errors section. The %FAILEDPLUGINS% variable can be used to debug failures. You may also want to check your webserver error log and the various TWiki log files.

Some Notes on Plugin Performance

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The performance of the system depends to some extent on the number of Plugins installed and on the Plugin implementation. Some Plugins impose no measurable performance decrease, some do. For example, a Plugin might use many Perl libraries that need to be initialized with each page view (unless you run mod_perl). You can only really tell the performance impact by installing the Plugin and by measuring the performance with and without the new Plugin. Use the TWiki:Plugins.PluginBenchmarkAddOn, or test manually with the Apache ab utility. Example on Unix:
time wget -qO /dev/null /twiki/bin/view/TWiki/AbcPlugin
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The performance of the system depends to some extent on the number of Plugins installed and on the Plugin implementation. Some Plugins impose no measurable performance decrease, some do. For example, a Plugin might use many Perl libraries that need to be initialized with each page view (unless you run mod_perl). You can only really tell the performance impact by installing the Plugin and by measuring the performance with and without the new Plugin. Use the TWiki:Plugins.PluginBenchmarkAddOn, or test manually with the Apache ab utility. Example on Unix:
time wget -qO /dev/null /twiki/bin/view/TWiki/AbcPlugin
  TIP If you need to install an "expensive" Plugin, but you only need its functionality only in a subset of your data, you can disable it elsewhere by defining the %DISABLEDPLUGINS% TWiki variable.
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Define DISABLEDPLUGINS to be a comma-separated list of names of plugins to disable. Define it in Main.TWikiPreferences to disable those plugins everywhere, in the WebPreferences topic to disable them in an individual web, or in a topic to disable them in that topic. For example,
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Define DISABLEDPLUGINS to be a comma-separated list of names of plugins to disable. Define it in Main.TWikiPreferences to disable those plugins everywhere, in the WebPreferences topic to disable them in an individual web, or in a topic to disable them in that topic. For example,
 
   * Set DISABLEDPLUGINS = SpreadSheetPlugin, EditTablePlugin
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Plugin Evaluation Order

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By default, TWiki executes Plugins in alphabetical order on Plugin name. It is possible to change the order, for example to evaluate database variables before the speadsheet CALCs. This can be done with {PluginsOrder} in the Plugins section of configure.
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By default, TWiki executes Plugins in alphabetical order on Plugin name. It is possible to change the order, for example to evaluate database variables before the spreadsheet CALCs. This can be done with {PluginsOrder} in the Plugins section of configure.
 

Plugin-Specific Settings

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  Plugin status variables let you list all active Plugins wherever needed.
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This site is running TWiki version TWiki-6.0.2, Sun, 29 Nov 2015, build 29687, Plugin API version 6.02

 

%ACTIVATEDPLUGINS%

On this TWiki site, the enabled Plugins are: SpreadSheetPlugin, BackupRestorePlugin, ColorPickerPlugin, CommentPlugin, DatePickerPlugin, EditTablePlugin, HeadlinesPlugin, InterwikiPlugin, JQueryPlugin, PreferencesPlugin, SetGetPlugin, SlideShowPlugin, SmiliesPlugin, TablePlugin, TagMePlugin, TinyMCEPlugin, TwistyPlugin, WatchlistPlugin, WysiwygPlugin.

%PLUGINDESCRIPTIONS%

  • SpreadSheetPlugin (2015-06-07, $Rev: 29570 (2015-11-29) $): Add spreadsheet calculation like "$SUM( $ABOVE() )" to TWiki tables or anywhere in topic text
  • BackupRestorePlugin (2015-01-09, $Rev: 28636 (2015-11-29) $): Administrator utility to backup, restore and upgrade a TWiki site
  • ColorPickerPlugin (2015-01-10, $Rev: 29507 (2015-11-29) $): Color picker, packaged for use in TWiki forms and TWiki applications
  • CommentPlugin (2015-01-10, $Rev: 28648 (2015-11-29) $): Quickly post comments to a page without an edit/preview/save cycle
  • DatePickerPlugin (2015-01-10, $Rev: 29510 (2015-11-29) $): Pop-up calendar with date picker, for use in TWiki forms, HTML forms and TWiki plugins
  • EditTablePlugin (2015-01-10, $Rev: 29516 (2015-11-29) $): Edit TWiki tables using edit fields, date pickers and drop down boxes
  • HeadlinesPlugin (2015-11-06, $Rev: 29650 (2015-11-29) $): Show headline news in TWiki pages based on RSS and ATOM news feeds from external sites
  • InterwikiPlugin (2015-06-18, $Rev: 29526 (2015-11-29) $): Write ExternalSite:Page to link to a page on an external site based on aliases defined in a rules topic
  • JQueryPlugin (2015-01-10, $Rev: 29532 (2015-11-29) $): jQuery JavaScript library for TWiki
  • PreferencesPlugin (2015-01-14, $Rev: 29550 (2015-11-29) $): Allows editing of preferences using fields predefined in a form
  • SetGetPlugin (2015-07-09, $Rev: 29564 (2015-11-29) $): Set and get variables and JSON objects in topics, optionally persistently across topic views
  • SlideShowPlugin (2015-01-14, $Rev: 29566 (2015-11-29) $): Create web based presentations based on topics with headings.
  • SmiliesPlugin (2015-02-16, $Rev: 29568 (2015-11-29) $): Render smilies as icons, like  :-)  as smile or  :eek:  as eek!
  • TablePlugin (2015-02-16, $Rev: 29580 (2015-11-29) $): Control attributes of tables and sorting of table columns
  • TagMePlugin (2015-02-16, $Rev: 29582 (2015-11-29) $): Tag wiki content collectively or authoritatively to find content by keywords
  • TinyMCEPlugin (2015-02-16, $Rev: 29584 (2015-11-29) $): Integration of the Tiny MCE WYSIWYG Editor
  • TwistyPlugin (2015-04-28, $Rev: 29600 (2015-11-29) $): Twisty section JavaScript library to open/close content dynamically
  • WatchlistPlugin (2015-01-15, $Rev: 28820 (2015-11-29) $): Watch topics of interest and get notified of changes by e-mail
  • WysiwygPlugin (2015-02-16, $Rev: 29604 (2015-11-29) $): Translator framework for WYSIWYG editors
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%FAILEDPLUGINS%

PluginErrors
SpreadSheetPlugin none
BackupRestorePlugin none
ColorPickerPlugin none
CommentPlugin none
DatePickerPlugin none
EditTablePlugin none
HeadlinesPlugin none
InterwikiPlugin none
JQueryPlugin none
PreferencesPlugin none
SetGetPlugin none
SlideShowPlugin none
SmiliesPlugin none
TablePlugin none
TagMePlugin none
TinyMCEPlugin none
TwistyPlugin none
WatchlistPlugin none
WysiwygPlugin none
HandlerPlugins
afterEditHandlerWysiwygPlugin
afterRenameHandlerTagMePlugin
WatchlistPlugin
afterSaveHandlerTagMePlugin
WatchlistPlugin
beforeCommonTagsHandlerEditTablePlugin
PreferencesPlugin
TwistyPlugin
WysiwygPlugin
beforeEditHandlerTinyMCEPlugin
WysiwygPlugin
beforeMergeHandlerWysiwygPlugin
beforeSaveHandlerCommentPlugin
WatchlistPlugin
WysiwygPlugin
commonTagsHandlerSpreadSheetPlugin
BackupRestorePlugin
CommentPlugin
EditTablePlugin
JQueryPlugin
SlideShowPlugin
SmiliesPlugin
initPluginSpreadSheetPlugin
BackupRestorePlugin
ColorPickerPlugin
CommentPlugin
DatePickerPlugin
EditTablePlugin
HeadlinesPlugin
InterwikiPlugin
JQueryPlugin
PreferencesPlugin
SetGetPlugin
SlideShowPlugin
SmiliesPlugin
TablePlugin
TagMePlugin
TinyMCEPlugin
TwistyPlugin
WatchlistPlugin
WysiwygPlugin
modifyHeaderHandlerWysiwygPlugin
postRenderingHandlerPreferencesPlugin
WysiwygPlugin
preRenderingHandlerInterwikiPlugin
SmiliesPlugin
TablePlugin
19 plugins

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  • For example, use an eval block like this:
    eval { require IPC::Run }
    return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@;
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  • You can use a flag to avoid running the initialization twice
  • The TWiki:Plugins.PluginBenchmarkAddOn comes in handy to measure and fine-tune the performance of your Plugin
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  • Keep the main plugin package as small as possible; create other packages that are loaded if and only if they are used. For example, create sub-packages of BathPlugin in lib/TWiki/Plugins/BathPlugin/.
  • Avoid using preferences in the plugin topic; set $NO_PREFS_IN_TOPIC if you possibly can, as that will stop TWiki from reading the plugin topic for every page. Use Config.spec instead.
  • Use registered tag handlers
  • Measure the performance to see the difference
 
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Plugin Version Detection

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Version Detection

 
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To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.
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To eliminate the incompatibility problems that are bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.
 
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  • All modules require a $VERSION='0.000' variable, beginning at 1.000.
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  • All plugin packages require a $VERSION variable. This should be an integer, or a subversion version id.
 
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  • The initPlugin handler should check all dependencies and return TRUE if the initialization is OK or FALSE if something went wrong.
    • The Plugin initialization code does not register a Plugin that returns FALSE (or that has no initPlugin handler).
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  • The initPlugin handler should check all dependencies and return 1 if the initialization is OK or 0 if something went wrong.
    • The Plugin initialization code does not register a Plugin that returns 0 (or that has no initPlugin handler).
 
  • $TWiki::Plugins::VERSION in the TWiki::Plugins module contains the TWiki Plugin API version, currently 6.02.
    • You can also use the %PLUGINVERSION{}% variable to query the Plugin API version or the version of installed Plugins.
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Anatomy of a Plugin

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A basic TWiki Plugin consists of two elements:
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A (very) basic TWiki Plugin consists of two files:
 
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  • a Perl module, ex: MyFirstPlugin.pm
  • a documentation topic, ex: MyFirstPlugin.txt
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  • a Perl module, e.g. MyFirstPlugin.pm
  • a documentation topic, e.g. MyFirstPlugin.txt
 
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The Perl module can be a block of code that connects with TWiki alone, or it can include other elements, like other Perl modules (including other Plugins), graphics, TWiki templates, external applications (ex: a Java applet), or just about anything else it can call.
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The Perl module can be a block of code that talks to with TWiki alone, or it can include other elements, like other Perl modules (including other Plugins), graphics, TWiki templates, external applications (ex: a Java applet), or just about anything else it can call.
 In particular, files that should be web-accessible (graphics, Java applets ...) are best placed as attachments of the MyFirstPlugin topic. Other needed Perl code is best placed in a lib/TWiki/Plugins/MyFirstPlugin/ directory.

The Plugin API handles the details of connecting your Perl module with main TWiki code. When you're familiar with the Plugin API, you're ready to develop Plugins.

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The TWiki::Plugins.BuildContrib module provides a lot of support for plugins development, including a plugin creator, automatic publishing support, and automatic installation script writer. If you plan on writing more than one plugin, you probably need it.
 

Creating the Perl Module

Copy file lib/TWiki/Plugins/EmptyPlugin.pm to <name>Plugin.pm. The EmptyPlugin.pm module contains mostly empty functions, so it does nothing, but it's ready to be used. Customize it. Refer to the Plugin API specs for more information.

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 $var = MyFirstPlugin::Attrs->new();
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Measuring and Improving the Plugin Performance

A high quality Plugin performs well. You can use the TWiki:Plugins.PluginBenchmarkAddOn to measure your TWiki:Plugins.PluginBenchmarks. The data is needed as part of the Documentation Topic.

See also Hints on Writing Fast Plugins.

 

Writing the Documentation Topic

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The Plugin documentation topic contains usage instructions and version details. It serves the Plugin files as FileAttachments for downloading. (The doc topic is also included in the distribution package.) To create a documentation topic:
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The Plugin documentation topic contains usage instructions and version details. It serves the Plugin files as FileAttachments for downloading. (The doc topic is also included in the distribution package.) To create a documentation topic:
 
  1. Copy the Plugin topic template from TWiki.org. To copy the text, go to TWiki:Plugins/PluginPackage and:
    • enter the Plugin name in the "How to Create a Plugin" section
    • click Create
    • select all in the Edit box & copy
    • Cancel the edit
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    • go back to your site to the TWiki web
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    • go back to your site to the TWiki web
 
    • In the GoBox enter your Plugin name, for example MyFirstPlugin, press enter and create the new topic
    • paste & save new Plugin topic on your site
  1. Customize your Plugin topic.
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  Plugin Settings: <Description and settings for custom Plugin %VARIABLES%, and those required by TWiki.>"
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  • Plugins Preferences <If user settings are needed, explain... Entering values works exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:>"
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  • Plugins Preferences <If user settings are needed, explain... Entering values works exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:>"
 
    • Set <EXAMPLE = value added>

Plugin Installation Instructions: <Step-by-step set-up guide, user help, whatever it takes to install and run, goes here.>"

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    • data/TWiki/MyFirstPlugin.txt
    • pub/TWiki/MyFirstPlugin/uparrow.gif
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Measuring and Improving the Plugin Performance

A high quality Plugin performs well. You can use the TWiki:Plugins.PluginBenchmarkAddOn to measure your TWiki:Plugins.PluginBenchmarks. The data is needed as part of the Documentation Topic.

See also Hints on Writing Fast Plugins.

 

Publishing for Public Use

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Plugin Internal Data

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You can create a Plugin "work area" using the TWiki::Func::getWorkArea() function, which gives you a persistant directory where you can store data files. By default they will not be web accessible. The directory is guaranteed to exist, and to be writable by the webserver user. For convenience, TWiki::Func::storeFile() and TWiki::Func::readFile() are provided to persistently store and retrieve simple data in this area.
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You can create a Plugin "work area" using the TWiki::Func::getWorkArea() function, which gives you a persistent directory where you can store data files. By default they will not be web accessible. The directory is guaranteed to exist, and to be writable by the webserver user. For convenience, TWiki::Func::storeFile() and TWiki::Func::readFile() are provided to persistently store and retrieve simple data in this area.
 

Web Accessible Data

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  • Use only alphanumeric characters, underscores, dashes and periods to avoid platform dependency issues and URL issues
  • Example: _Main_roundedge-ul.gif
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Integrating with configure

Some TWiki extensions have setup requirements that are best integrated into configure rather than trying to use TWiki preferences variables. These extensions use Config.spec files to publish their configuration requirements.

Config.spec files are read during TWiki configuration. Once a Config.spec has defined a configuration item, it is available for edit through the standard configure interface. Config.spec files are stored in the 'plugin directory' e.g. lib/TWiki/Plugins/BathPlugin/Config.spec.

Structure of a Config.spec file

The Config.spec file for a plugin starts with the plugin announcing what it is:
# ---+ BathPlugin
# This plugin senses the level of water in your bath, and ensures the plug
# is not removed while the water is still warm.
This is followed by one or more configuration items. Each configuration item has a type, a description and a default. For example:
# **SELECT Plastic,Rubber,Metal**
# Select the plug type
$TWiki::cfg{BathPlugin}{PlugType} = 'Plastic';

# **NUMBER**
# Enter the chain length in cm
$TWiki::cfg{BathPlugin}{ChainLength} = '30';

# **BOOLEAN EXPERT**
# Turn this option off to disable the water temperature alarm
$TWiki::cfg{BathPlugin}{TempSensorEnabled} = '1';
The type (e.g. **SELECT** ) tells configure to how to prompt for the value. It also tells configure how to do some basic checking on the value you actually enter. All the comments between the type and the configuration item are taken as part of the description. The configuration item itself defines the default value for the configuration item. The above spec defines the configuration items $TWiki::cfg{BathPlugin}{PlugType}, $TWiki::cfg{BathPlugin}{ChainLength}, and $TWiki::cfg{BathPlugin}{TempSensorEnabled} for use in your plugin. For example,
if( $TWiki::cfg{BathPlugin}{TempSensorEnabled} && $curTemperature > 50 ) {
    die "The bathwater is too hot for comfort";
}

The config.spec file is read by configure, and configure then writes LocalSite.cfg with the values chosen by the local site admin.

A range of types are available for use in Config.spec files:

BOOLEAN A true/false value, represented as a checkbox
COMMAND length A shell command
LANGUAGE A language (selected from {LocalesDir}
NUMBER A number
OCTAL An octal number
PASSWORD length A password (input is hidden)
PATH length A file path
PERL A perl structure, consisting of arrays and hashes
REGEX length A perl regular expression
SELECT choices Pick one of a range of choices
SELECTCLASS root Select a perl package (class)
STRING length A string
URL length A url
URLPATH length A relative URL path

All types can be followed by a comma-separated list of attributes.

EXPERT means this an expert option
M means the setting is mandatory (may not be empty)
H means the option is not visible in configure

See lib/TWiki.spec for many more examples.

Config.spec files are also used for other (non-plugin) extensions. in this case they are stored under the Contrib directory instead of the Plugins directory.

 

Maintaining Plugins

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  The Plugin interface (TWikiFuncDotPm functions and handlers) evolve over time. TWiki 4.0 introduced new API functions to address the needs of Plugin authors. It also deprecated some functions. Some Plugins written for earlier TWiki releases using unofficial TWiki internal functions no longer work on the TWiki 4.0 codebase. All this means that some Plugins need to be updated to work on the TWiki 4.0 codebase.
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Organizations typically do not upgrade to the latest TWiki for many months. However, many administrators still would like to install the latest versions of a Plugin on their older TWiki installation. This need is fullfilled if Plugins are maintained in a compatible manner.
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Organizations typically do not upgrade to the latest TWiki for many months. However, many administrators still would like to install the latest versions of a Plugin on their older TWiki installation. This need is fulfilled if Plugins are maintained in a compatible manner.
  TIP Tip: Plugins can be written to be compatible with older and newer TWiki releases. This can be done also for Plugins using unofficial TWiki internal functions of an earlier release that no longer work on the latest TWiki codebase. TWiki:TWiki.TWikiPluginsSupplement#MaintainPlugins has more.
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  Related Topics: DeveloperDocumentationCategory, AdminDocumentationCategory, TWiki:TWiki.TWikiPluginsSupplement
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-- Contributors: TWiki:Main.PeterThoeny, TWiki:Main.AndreaSterbini, TWiki:MainMikeMannix, TWiki:CrawfordCurrie
 
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