Information Technology Reference
In-Depth Information
The information viewpoint concentrates on the modelling of the shared
information manipulated within the enterprise of interest. The creation of an
information specification has broadly the same objectives that creation of a
data dictionary had for previous generations. By providing a common model
that can be referenced from throughout a complete piece of design, we can
ensure that the same interpretation of information is applied at all points.
As a result, we can avoid the divergence of use and incomplete collection of
information that would result from separate members of the design team each
making their own decisions about interpretation.
As an ideal, we would like there to be a single universal information model,
but this is clearly not practical. The aim here, therefore, is to achieve a shared
model for the particular design activity, but we shall see later that even this
may not be achievable when we are considering federation of systems or legacy
integration. The best we can achieve is a single model used within the scope of
a particular design authority. However, this is already suciently challenging,
while giving potential for huge quality improvements.
The computational viewpoint is concerned with the development of the
high-level design of the processes and applications supporting the enterprise
activities. It uses the familiar tools for object-oriented software design, ex-
pressing its models in terms of objects with strong encapsulation boundaries,
interacting at typed interfaces by performing a sequence of operations (or
passing continuous streams of information). The computational specification
makes reference to the information viewpoint for the definitions of data objects
and their behavioural constraints.
The computational design is abstract in that its objects are not placed at
specific locations and allocated particular resources to run on; this is done
elsewhere. The same design can be implemented in many different ways by
placing its objects on different platforms.
The engineering viewpoint tackles the problem of diversity in infrastruc-
ture provision; it gives the prescriptions for supporting the necessary abstract
computational interactions in a range of different situations. It thereby of-
fers a way to avoid lock-in to specific platforms or infrastructure mechanisms.
A particular interaction may involve communication between subsystems, or
between objects co-located in a single application server, and different engi-
neering solutions will be used depending on which is currently the case. The
engineering specification is akin to the specification of how middleware is pro-
vided; there are different solutions for use in different operating environments,
but the aim is to provide a consistent set of communication services and other
supporting services that the application designer can rely on in all cases.
The engineering viewpoint in ODP is also concerned with the provision
to the computational designer of a set of guarantees, called transparencies.
Providing a transparency involves taking responsibility for a distribution prob-
lem, so that the computational design does not need to worry about it.
Many of the mechanisms needed are nowadays available in the form of
standard middleware or web services components, simplifying the engineering
