It is quite common to describe systems with
respect to their input/output functionalities. As a first step, we
have to clarify the borderline between the components of the RM and
external entities.
Presentation goals and commands form the triggering input to an
IMMPS. While being processed through the layers together with
application data/knowledge, goals/commands are eventually transformed
into presentations composed of media objects. This view is reflected
in Fig. 3 through the ellipses called Goal Formulation,
Application, and User who is the presentation consumer.
Although in many concrete system implementations Goal
Formulation and Application appear as a single component, we
distinguish them to emphasize the difference between the
availability of application knowledge/data, and the use
of that knowledge/data to satisfy presentation goals. While we may
assume the presentation consumer is a human user, goal formulation
may be done either by a human (e.g., using a keyboard to type in goals, or
selecting predefined goals from a menu) or computer. In the case of a human,
we do not further differentiate whether the goal formulator and the
presentation consumer are identical. This aspect should be
reflected in the user model of a concrete system.
As presentation systems are typically not stand-alone applications but parts of user interfaces of complex systems, there are often further interfaces to external components. This is the case, for example, when describing an IMMPS which acquires some knowledge from external knowledge bases, or directly from the user. Although not explicitly handled here, interactions with external unspecified systems/entities might be modeled by means of data capture metafiles as in the Computer Graphics Reference Model [3].