RSS Support

From the specification,

RDF Site Summary (RSS) is a lightweight multipurpose extensible metadata description and syndication format. RSS is an XML application, conforms to the W3C's RDF Specification and is extensible via XML-namespace and/or RDF based modularization.

1. Feed generation

• the site context whose content is to be summarized,
• how to retrieve the various required and optional metadata fields
• whether any changes have been made since the last summary was built
• how often to rebuild the summary (if changes are present)

Usage scenarios

• Publisher wishes to syndicate the Bar Forum in the Foo Bboard package instance.
• Luckily, the bboard package implements the summary service contract for context type bboard:forum of which the Bar Forum is an example.
• Programmer registers the context identifier for the Bar Forum with summary service, indicating that the summary should be built no more than once per hour.
• Summary is available at /some/url/specific/to/bar/forum/summary.xml

Service contract

The feed generation service contract is called RssGenerationSubscriber and consists of two operations.

1. Datasource(context_identifier) returns a data structure that contains all required metadata fields plus configuration information such as the RSS version to be used (0.91 or 1.00 are supported at present). This data structure contains everything needed to run rss_gen.
2. LastUpdated(context_identifier) returns a timestamp that is used to determine if the live summary is out of date.

Under the hood

Implementation suggestions:

1. All summaries are static files. We will devise an appropriate file-naming scheme.
2. A programmer registers a context with the summary service through API functions (we can make it possible through web UI as well if that makes sense).
3. A summary context is a content-containing domain which implements the summary service contract. A summary context is not identical to a package instance. For example, a single bboard package instance might contain 3 summary contexts, one for each of the forums in the instance.
4. A scheduled proc runs through all registered contexts, checking to see if the live summary is stale and also if the minimum "quiet time" has elapsed.
5. If the conditions for rebuild are met for a context, the scheduled proc pulls out the context's summary data via Datasource and uses the information to build a new summary page. This generic and simple scheme can be used to dispatch different versions of the summary builder as well as to support extensibility via modules. Warning: This design expects the output of Datasource to be reasonably small, as we will have to parse this list-of-lists to generate a summary.

2. Feed Parsing