Feed Data Type Application Classes

The feed data type application class (PTFP_FEED:DataSource:DataSource) bridges the data and the feed definition. It has two roles:

  • At design time, it provides information to the framework about how to define the feed definition for this type of data.

  • At runtime, the framework uses the application class to collect feed data.

Design Time Role of Application Classes

At design time, the feed data type application class provides information about a specific type of data to the framework, including a list of data source settings, list of data source parameters and their default values, data security, and name of the default feed service definition. The feed data type application class handles events such as processes that occur when you delete a feed definition. The framework uses all of this information in the feed definition creation and maintenance.

Every feed data type may have zero to three data source settings. The data source settings uniquely define the feed data source of the given type of data. You must define and store the values of the data source settings with the feed definition. The feed data type application class can also provide the prompt information for each data source setting.

Every feed data type may have zero or more data source parameters. The data source parameters are used to fine tune the feed or personalize the feed; for example, a news publication feed should include all child sections or a workspace feed should not include discussion data. Values of data source parameters are determined at runtime based on the usage type, fixed value, system variable value, user-specified value, and so on. The default values of data source parameters are stored with the feed definition. The Feed Data Type application class could provide the description, prompt information, default values, and default usage type for each data source parameter.

Runtime Role of Application Classes

At runtime, the runtime engine finds the feed definition and the associated feed data type application class based on the requested feed ID. It creates an instance of the feed data type application class associated with the specific feed definition, restores the data source setting values and the data source parameter values saved with the feed definition, evaluates the runtime values of those data source parameters based on their usage type, and sets other runtime information. It then executes the object to retrieve the content data of the feed.

The feed data type application class uses a feed-format-neutral object collection to temporarily store the data. It does not transform data to a feed document directly. This design enables application developers to expand the object model or use their own data objects. The advantages of using a feed-format-neutral object collection instead of the feed-format-specific XML document are:

  • It shields you from having to deal with the complex details of a specific feed format.

  • It minimizes the possibility of using a wrong XML element or structure.

  • It standardizes the use of specific elements within the feed.

  • It enables easier migration to newer feed format standards or a completely different feed format.

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