Just like a conventional collection, a DAC represents a group of related objects. A DAC is however distributed and can be accessed from various nodes of a network. In a way similar to a JAVASPACE, a DAC enables distributed participants to share information by pulling information from the space, but also by registering a callback object to be notified of future elements. DACs furthermore express through their type the qualities of service (QoS) they support. In other terms, we offer a framework of DAC subtypes representing different semantics and QoS. In this example, we will use a DAC representing a topic, to which application components subscribe with an optional content-based filter.