As with other approaches to e-learning
frameworks, the starting point is the abstraction
of service layers. We identify four layers of the framework:
User Agents interact with
users directly, such as portals, learning delivery systems,
authoring tools, administration interfaces and so on. User Agents based on this
framework can be either very small and focussed or span many processes to provide a
coherent workflow.
Application Services provide
functionality required by user agents, such as retrieving
learner information, or storing content in a repository. Application Services may be
implemented so that they have some sort of user interface, but the key requirement for
an application service is that it exposes its functionality for reuse by any number of user
agents or other application services, and that it implements a standard interface to
support this reuse
Common Services provide
lower-level functionality which is not education-specific,
such as authentication and authorization services, but upon which application services
and user agents depend.
Infrastructure is the underlying
network, storage, and processing capability provided for
an implementation. This is assumed by the framework, but not defined.
Figure 7: model of services
demonstrating common and application services
together with selected user agents
