Extensions

Getting Started

Deki Wiki "Hayes" introduces a new mechanism to add dynamic content to pages.  Dynamic content capabilities were introduced with Deki Wiki "Gooseberry", but adding custom extensions required changing the source code of the application.  With "Hayes", the dynamic content capabilities have been greatly improved and the implementation has been recast to leverage the new service-oriented architecture.  Adding extensions is now a simple registration step in the Control Panel using the Service Management pane.

Extensions are services that can either run locally or remotely.  Running an extension locally has the advantage of better bandwidth by not requiring additional network traffic.  However, in order to run an extension locally, it must be configured, which may sometimes require several steps, such as installing additional applications.  Alternatively, an extension can run remotely as a service on the intranet or internet.  In this case, it has been configured by someone else and is readily available for consumption.  A remotely running extension can be used by many Deki Wiki installations, making it easier to update the extension for all sites.

The following screen shots show how easy it is to add an extension service.

Control Panel

Service Management - List View

Service Management - Add Remote Service

 When adding an extension, there are several preference settings that can be applied to affect how it can be used:

• namespace: Overrides the extension's namespace.  Setting this preference to an empty string, removes the namespace prefix from the extension functions.
• title: Overrides the extension title in the documentation page.
• description: Adds a custom description text to the extension in the documentation page.

What can you do with Extensions?

Deki Wiki includes several extensions out of the box, which make it easy to embed dynamic content into wiki pages.

Flickr Service Slideshows & Badges	Google Service Google Maps with marker and pop-up bubble
Graphviz Service Generate complex graphs	ImageMagick Service Apply effects to images
MathService Advanced math formulae rendering	Yahoo Service Show stock information and charts

How do you use Extensions?

An extension defines a set of functions, which become available when the service is enabled in the Control Panel.  These functions can be invoked in different ways.

The most common use for simple invocations is done directly inline using the double-curly brace notation {{...}}.  The following function will include a page called "My Page".

{{wiki.page("My page")}} 

Another common use is to put the invocation inside a <pre class="script"> block.  The <pre> notation has the advantage that it can span multiple lines without interference from other markup.

<pre class="script">wiki.page("My Page")</pre> 

The last notation is a bit special, but lends itself well for functions that can take a large string argument.  It also uses the <pre class="script"> notation, but adds one more attribute that specifies the function to invoke.  For example <pre class="script" function="function-name">.  The contents of the <pre> block are then passed in as a string as the first argument.

<pre class="script" function="wiki.page">My Page</pre> 

What Extensions are available?

DekiWiki ships with a dozen extensions for Google, Windows Live, Flickr, and many others.  All extensions are setup in a similar manner, but some extension have prerequisites before they can be used.  Consult the documentation for each extension to see what is needed to set it up.

What data types do Extensions support?

Extensions use a small set of data types.  They are

• nil - the empty value (i.e. nil, null)
• bool - a boolean value (i.e. true, false)
• num - an integer or floating-point number (e.g. 1, -5, 0.6)
• string - a sequence of characters (e.g. "Hello World")
• uri - a uniform resource identifier (only used internally)
• map - an associative array (e.g. { a : 1, b : 2 })
• list - an indexed array (e.g. [ 1, 2, "a" ])
• xml - an xml document (only used internally)

How do you create your own Extensions using .Net?

 Refer here for a step-by-step tutorial on creating a new extension.

How do you create your own Extensions without .Net?

Extensions use a simple document exchange protocol for registering and invocation.  This makes it possible to write extensions in any language.

<extension>
    <title>MindTouch Deki Math Service</title>
    <copyright>Copyright (c) 2007 MindTouch, Inc.</copyright>
    <uri.help>http://doc.opengarden.org/Deki_API/Reference/Math</uri.help>
    <namespace>math</namespace>
    <function>
        <name>formula</name>
        <uri>http://ext.mindtouch.com:8080/math/formula</uri>
        <return type="xml />
        <param name="formula" type="str">formula in Latex-AMS notation</param>
    </function>
</extension>

{{math.formula("\\pi=\\frac{3}{4} \\sqrt{3}+24 \\int_0^{1/4}{\\sqrt{x-x^2}dx}")}}

<value type="list">
    <value key="#" type="str">\pi=\frac{3}{4} \sqrt{3}+24 \int_0^{1/4}{\sqrt{x-x^2}dx}</value>
</value>

<value type="doc">
    <value key="#" type="xml">
        <html>
            <body>
                <img src="http://ext.mindtouch.com:8080/host/$store/_x002F_math/806b359f-94ef-3aae-e253-2877a0af8a8c.img" />
            </body>
        </html>
    </value>
</value>

Factory Included Extension Services