Microsoft SharePoint 2007 Technologies

466 16.3 Feature Architecture

hidden Feature. The PublishingLayouts Feature is activated upon site collec-

tion creation and provisions all the files and images listed in the Feature defi-

nition into the appropriate document library, such as placing master pages in

the master page gallery. This is just one example of how the implementation

of Features provides core functionality to SharePoint. Examining each of the

default Features in the

FeatureS directory can give you a good understand-

ing of the capabilities that Features bring to the table.

16.3 Feature Architecture

We have stated that a Feature is a package of components that implements a

specific piece of functionality to your SharePoint deployment. But what

does this actually mean, and what does a Feature physically look like? At the

very basic level, a Feature is a folder containing one or more files that define

and deliver the functionality. As previously mentioned, all Feature folders

reside in the

\Program Files\Common Files\Microsoft Shared\Web

server extensions\12\TEMPLATE\FeatureS

directory. If you examine

each of the default Microsoft Feature folders, you will see they each contain

a Feature definition file (Feature.xml). The Feature definition file contains a

Feature element that defines the necessary attributes, properties, activation

dependencies, paths to element definition files, and references to receiver

assemblies. The structure of the

Feature element is shown in Figure 16.3.

The child elements,

ActivationDependencies, ElementManifests,

and

Properties, are all optional elements each further defining the Feature.

We will revisit each of these child elements in a moment, but for now let’s

Figure 16.3

Feature.XML

structure.

16.3 Feature Architecture 467

Chapter 16

focus on the parent element. Attributes of the parent Feature element spec-

ify characteristics such as the title of the Feature as it would appear on the

Feature settings page in the browser user interface. Figure 16.4 and Table

16.1 describe the attributes that are associated with the

Feature element.

Note that only the Feature

Id and the Scope attributes are required for a Fea-

ture to successfully install. A Feature containing these two attributes alone

would not be very useful, but it would install nonetheless, and appear in the

Feature settings page of the specified scope.

The

Scope attribute allows you to define where the Feature will be acti-

vated and on which Feature settings page it will appear. This setting is

restricted to one of the following choices:

Farm, WebApplication, Site, and

Web. If the Scope attribute is set to Farm then the Feature is installed at the

farm level and, if not hidden, appears on the Manage Farm Features page

accessible from the Operations page in the central administration user inter-

face. Features scoped at the farm level are activated automatically by default;

however, this behavior can be controlled by setting the

ActivateOnDefault

Feature attribute. If the Scope attribute is set to WebApplication, the Feature

is installed at the Web application level and, if not hidden, appears on the

Manage Web Application Feature page accessible from the Application Man-

agement page in the central administration user interface. Features scoped at

the Web application level are not automatically activated by default. Again,

this behavior can be controlled by setting the

ActivateOnDefault Feature

attribute. However, this only affects newly created Web applications, existing

Web applications still need to be activated. If the

Scope attribute is set to

Site, the Feature is installed at the site collection level and, if not hidden,

appears on the Site Collection Features page accessible from the Site Settings

Figure 16.4

Feature element

attributes.

468 16.3 Feature Architecture

page at the root of the site collection. If the Scope attribute is set to Web, the

Feature is installed at the individual Web site level and, if not hidden, appears

on the Site Features page accessible from the Web site’s Site Settings page. Fea-

tures scoped at the site collection level and the Web site level are not activated

by default and, unlike the

Farm and WebApplication scoping, this behavior

cannot be controlled by the

ActivateOnDefault attribute. It should be

noted, however, that Features scoped at the site collection and Web site levels

are automatically activated upon site creation if they are associated, or stapled,

to a site definition. We’ll discuss the detail of Feature activation and Feature

stapling later in the chapter.

Another important factor that influences the scope of your Feature is

the element type that you are implementing. For example, if you are using

Features to create a content type, then your Feature must be scoped to the

site collection level, as content type Features are not supported at the Web

site, Web application, and Farm levels. The Elements By Scope section of

the WSS 3.0 SDK provides a complete listing of the supported element

types for each scope.

Figure 16.5

Element manifests.