Content Exchange Concepts

ICE Protocol

The content distribution service is based on the manufacturer-independent Information and Content Exchange Protocol (ICE) of the World Wide Web Consortium (W3C). The ICE protocol regulates the exchange of content between a syndicator and a subscriber (see below). The protocol information and the content are sent as XML documents. This enables the exchange of content between third-party providers that support the ICE protocol as well as between repositories that are connected to Knowledge Management.

Syndicator and Subscriber

There are two parties involved in the content exchange service:

• A syndicator who aggregates content in subscription offers.

• A subscriber who subscribes to particular offers.

A syndicator can distribute content to more than one subscriber. A subscriber can receive content from more than one syndicator. A content manager using the content exchange service can also act as a syndicator of content created at his or her site and be a subscriber to content created at another site at the same time.

Subscription Offers and Subscriptions

A syndicator creates offers that specify the content to be delivered and details on how it will be delivered and updated. By accepting an offer, the subscriber establishes a subscription that governs the actual content transfer.

Architecture of the Content Exchange Service

An offer contains one or more components, each of which defines content that is made available through the offer. It also comprises one or more delivery rules. A delivery rule specifies a delivery mode ( push or pull ) and a delivery schedule. If a subscriber accepts an offer that has multiple delivery rules, he or she has to decide on the delivery rule to be used for the subscription. Therefore, although offers can have multiple delivery rules, a subscription can have only a single one.

Transfer Channels

The delivery of content can take place using the following channels.

• Distributing Content Using HTTP

• Distributing Content (Offline)

Incremental Updates

The ICE protocol caters for incremental updates of content. To keep the volume of data low, only deltas are transported when an update takes place. The syndicator records information on which subscriber has received which document. It also records the time when the document was received. This information is stored in the syndicator's system in the document properties.

If you want to carry out an incremental update, all repositories that are referenced in an offer must support the application property service. If an offer contains a component that references a repository without an active application property service, the system carries out a full update of the entire offer.

When the system puts together an update package, it determines for each subscriber the documents that have been created, changed, or deleted since the last update. When a document is created or changed in the source repository, it is embedded in the ICE package. If a document has been deleted from the source repository, this information is transmitted to the subscriber, and the document is deleted accordingly from the target repository.