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Introducing the Windows RSS Platform

Introducing the Windows RSS Platform

This topic introduces the Windows RSS Platform, an API that developers can use to manipulate the Common Feed List, the set of feeds to which the user is subscribed. The properties and methods are categorized to provide a technical overview of the platform and its functionality.

This topic contains the following sections.

  • Introduction 
  • Object Model 
  • Common Feed List 
  • Working with Feeds 
  • RSS 2.0 Elements 
    • IFeed 
    • IFeedItem 
    • IFeedEnclosure 
  • Feed Synchronization 
  • Related Topics

Introduction

Really Simple Syndication (RSS) is an XML document format used by Web sites to publish frequently updated content, such as news headlines and blog posts. The distribution is called an RSS feed. In most cases, the RSS feed is retrieved directly from a Web server via HTTP. The RSS specification includes conventions that dictate how often feeds should be checked for updates.

As part of the RSS support in Windows Internet Explorer 7, users can discover and subscribe to RSS feeds within the browser. When the user subscribes to a feed, it is added to the Common Feed List, which is available for clients to use in addition to or instead of their own list. For example, in Microsoft Office Outlook® 2007, the user's subscription list can import feeds from the Common Feed List. This enables the discovery of feeds within Internet Explorer, and then for those discovered feeds to appear in other applications.

The Feed Download Engine downloads feeds and merges the new items with the existing data in the feed store. Using the Windows RSS Platform, applications can then expose the feed data to the user. The RSS Explorer of Windows Vista, for example, provides an excellent text reading experience for news and blog feeds, and Microsoft Windows Media Player enables users to listen to audio feeds. The consumption of feed data varies by application; the Windows RSS Platform makes a variety of scenarios possible by providing easy access to the feed data.

Object Model

The top-level object in the Windows RSS Platform is the FeedsManager object. To create the object for scripting, use the ProgID Microsoft.FeedsManager. To create the object for use with C/C++, call CoCreateInstance with CLSID_FeedsManager (defined in the msfeeds.h header file).

The Windows RSS Platform object model hierarchy is as follows:

Windows RSS Platform Object Model

The Windows RSS Platform supports both styles of Component Object Model (COM) interfaces:

  • Early-bound (vtable) interface—the interface that is better for C/C++ developers. These objects are in the IXFeedsManager hierarchy.
  • Late-bound IDispatch interface—COM Automation interface that is ideal for scripting and managed code (Microsoft Visual Basic .NET and C#). These are the IFeedsManager objects.

To avoid unnecessary repetition, the names of the COM Automation interfaces are used throughout this topic.

Common Feed List

The Common Feed List resembles a hierarchical file system with folders and feeds. The IFeedFolder interface contains properties and methods for accessing feeds contained within the folder as well as properties and methods for accessing subfolders. Because feed folders are mapped to disk directories, folder names are limited to those characters that the file system allows. (See Valid Feed and Folder Names for more information.)

The root folder of the Common Feed List is accessed through the FeedsManager.RootFolder property, which returns an object of type IFeedFolder. From there, each IFeedFolder object contains its own collection of subfolders and feeds. (Refer to the example in Subfolders for a demonstration of a recursive folder search that returns an aggregated total count of feeds.)

The following table lists the methods and properties that are used to traverse and manipulate the Common Feed List hierarchy.

Folder Method Returns Description
FeedsManager.RootFolder IFeedFolder Returns the top-level system feed folder.
FeedFolder.IsRoot Boolean Returns true if top-level folder.
FeedFolder.Subfolders IFeedsEnum Returns collection of subfolders.
FeedsManager.GetFolder(path) IFeedFolder Returns specific folder by path.
FeedFolder.GetSubfolder(name) IFeedFolder Returns specific subfolder.
FeedFolder.Name String Returns the name of the folder.
FeedFolder.Parent IFeedFolder Returns the parent folder.
FeedFolder.Path String Returns the feed list path of the folder.
FeedFolder.TotalItemCount Integer Returns an aggregated total of items in all feeds.
FeedFolder.TotalUnreadItemCount Integer Returns an aggregated total of unread items in all feeds.
Testing for Folders
FeedsManager.ExistsFolder(path) Boolean Returns true if folder exists.
FeedFolder.ExistsSubfolder(name) Boolean Returns true if subfolder exists.
Managing Folders
FeedFolder.CreateSubfolder(name) IFeedFolder Creates and returns new subfolder.
FeedsManager.DeleteFolder(path)   Deletes folder, including its subfolders and feeds.
FeedFolder.Delete   Deletes folder, including its subfolders and feeds.
FeedFolder.Move(path)   Moves the folder.
FeedFolder.Rename(name)   Renames the folder.

Working with Feeds

The IFeed interface exposes the required and optional elements of an RSS feed. To subscribe to a feed, assign it to a folder. The following table lists the methods and properties that are used to manage the feeds.

Feed Method Returns Description
FeedsManager.GetFeed(path) IFeed Returns specific feed, by feed list path.
FeedsManager.GetFeedByUrl(url) IFeed Returns specific feed, if subscribed, by URL.
FeedFolder.GetFeed(name) IFeed Returns specific feed by name.
FeedFolder.Feeds IFeedsEnum Returns collection of feeds.
Feed.Name String Returns the name of the feed.
Feed.Parent IFeedFolder Returns the parent folder of the feed.
Feed.Path String Returns the feed list path of the feed.
Testing for Feeds
FeedsManager.ExistsFeed(path) Boolean Returns true if feed exists.
FeedFolder.ExistsFeed(name) Boolean Returns true if feed exists.
FeedsManager.IsSubscribed(url) Boolean Returns true if a feed subscription exists.
Managing Feeds
FeedFolder.CreateFeed(name,url) IFeed Creates feed in folder and subscribes to it.
FeedsManager.DeleteFeed(path)   Deletes the feed.
Feed.Delete   Deletes the feed.
Feed.Move(path)   Moves the feed.
Feed.Rename(name)   Renames the feed.

RSS 2.0 Elements

Most of the XML elements of an RSS 2.0 feed are available as read-only properties on the associated objects. Although some channel elements (such as cloud, rating, skipDays, and skipHours) are not available as properties on the IFeed interface, they are still in the XML source for the feed. Additional namespace extensions define properties that are used by the Windows RSS Platform to manage lists.

IFeed

The IFeed interface exposes the properties that are present on the RSS channel element.

Feed Elements Type Description
Feed.Copyright String Optional. Returns the channel copyright.
Feed.Description String Required. Returns the channel description.
Feed.Image String Optional. Returns the URL of the feed logo.
Feed.Language String Optional. Returns the language code for the feed.
Feed.LastBuildDate Floating-point number Optional. Returns the date of last content change.
Feed.Link String Required. Returns the homepage URL of the feed.
Feed.PubDate Floating-point number Optional. Returns the publication date for feed content.
Feed.Title String Required. Returns the title of the feed.
Feed.Ttl String Optional. Returns the time to live (TTL) of the feed.
XML Source
Feed.Xml(count,sort,filter,include) String Returns a new XML document for the feed.
Common Feed List Properties
Feed.DownloadUrl String Returns URL used for security zone mapping.
Feed.IsList Boolean Returns true if the feed contains list extensions.
Feed.ItemCount Integer Returns count of items.
Feed.Items IFeedsEnum Returns collection of items.
Feed.LastWriteTime String Returns the date and time of creation or last modification.
Feed.LocalEnclosurePath String Returns the system folder where downloaded enclosures are saved.
Feed.LocalId String Returns the GUID assigned to the feed.
Feed.MarkAllItemsRead String Sets the read status of all items to true.
Feed.Name String Returns the name of the feed.
Feed.Parent IFeedFolder Returns the parent folder of the feed.
Feed.Path String Returns the feed list path of the feed.
Feed.UnreadItemCount Integer Returns the count of unread items.
Feed.Url String Returns the source URL of the feed.

IFeedItem

Individual items in a feed are represented by FeedItem objects. Depending on the type of feed, these items are aggregated as news items that are merged into the feed, or as list items that replace the contents of the previous list. Additional RSS 2.0 item elements, such as GUID and source, are available in the XML source document of the feed.

Item Elements Type Description
FeedItem.Author String Optional. Returns the e-mail address of the author.
FeedItem.Comments String Optional. Returns the page URL of related comments.
FeedItem.Description String Required. Returns the item synopsis.
FeedItem.Guid String Optional. Returns the GUID of the item.
FeedItem.Link String Required. Returns the source URL of the item.
FeedItem.Modified Floating-point number Optional. Returns the date and time of last modification.
FeedItem.PubDate Floating-point number Optional. Indicates the date of the item publication.
FeedItem.Title String Required. Returns the title of the item.
XML Source
FeedItem.Xml(include) String Returns an XML fragment for the item.
Common Feed List Properties
FeedItem.DownloadUrl String Returns the URL used for security zone mapping.
FeedItem.Enclosure IFeedEnclosure Returns the enclosure (media object) associated with the item.
FeedItem.IsRead Boolean Returns true if the item has been viewed.
FeedItem.LocalId Integer Returns the ID assigned by the Feed Download Engine.
FeedItem.Parent IFeed Returns the parent feed.

IFeedEnclosure

The IFeedEnclosure interface provides access to the optional media file attachment that may be associated with each feed item.

Enclosure Attributes Type Description
FeedEnclosure.Length Integer Required. Returns the length in bytes of the enclosure.
FeedEnclosure.Type String Required. Returns the MIME type.
FeedEnclosure.Url String Required. Returns the source URL of the file.
Common Feed List Properties
FeedEnclosure.DownloadMimeType String Returns the final MIME type.
FeedEnclosure.DownloadUrl String Returns the URL used for security zone mapping.
FeedEnclosure.LocalPath String Returns the local system path of the downloaded file.
FeedEnclosure.Parent IFeedItem Returns the parent feed item.

Feed Synchronization

The Internet Explorer 7 aggregator (the Feed Download Engine) automatically downloads the feed items from the source URL specified in the feed. These downloads can occur on a schedule, or as requested by the user. The value of the Interval property and Ttl element of the feed determine how often the feed is downloaded; the feed is updated when the current time is equal to LastDownloadTime plus the maximum of these two values.

The following table lists the methods and properties that control the download and synchronization behavior of feeds:

Synchronization Properties Type Description
FeedsManager.BackgroundSync(action)   Possible actions are: Enable, Disable, or RunNow.
FeedsManager.BackgroundSyncStatus FEEDS_BACKGROUNDSYNC_STATUS Returns the status (Disabled, Enabled) of the Feed Download Engine.
FeedsManager.DefaultInterval Integer Returns, in minutes, the system-defined download interval.
FeedsManager.ItemCountLimit Integer Returns the upper limit of items that can be kept.
Feed.DownloadEnclosuresAutomatically Boolean Returns true if enclosures are automatically downloaded with the feed.
Feed.Interval Integer Returns, in minutes, how frequently the Feed Download Engine should download this feed.
Feed.MaxItemCount Integer Returns the number of items to keep when downloading this feed.
Feed.SyncSetting FEEDS_SYNC_SETTING Specifies whether to use the local or global interval setting, or disable automatic download entirely.
Feed.Ttl String Returns, in minutes, how long the feed should be cached according to the XML of the feed.
Synchronization Methods
FeedsManager.AsyncSyncAll   Forces update of all feeds, regardless of LastDownloadTime or Ttl.
Feed.Download   Downloads the feed and merges its contents into the system feed list.
FeedEnclosure.AsyncDownload   Downloads the enclosure.
FeedEnclosure.CancelAsyncDownload   Cancels a download operation in progress.
Success Indicators
Feed.LastDownloadTime Floating-point number Returns the date and time of the last successful download.
FeedItem.LastDownloadTime Floating-point number Returns the date and time of the last successful update.
Feed.LastDownloadError FEEDS_DOWNLOAD_ERROR Returns the download error of the feed, if any.
Feed.DownloadStatus FEEDS_DOWNLOAD_STATUS Returns the status of the feed.
FeedEnclosure.LastDownloadError FEEDS_DOWNLOAD_ERROR Returns the download error of the enclosure, if any.
FeedEnclosure.DownloadStatus FEEDS_DOWNLOAD_STATUS Returns the status of the enclosure.