Information Technology Reference
In-Depth Information
3.5 Relationship with Other Viewpoints
Although the different ODP viewpoints can be defined independently and
there is no explicit order imposed by the RM-ODP for specifying them, a
common practice is to start by developing the enterprise specification of the
system, and then prepare the information and computational specifications.
These specifications may place constraints on each other, and usually each
viewpoint specification is revised and refined as the others are developed.
In the case of a notional incremental development process of the ODP view-
point specifications, whereby the information specifications are developed tak-
ing into account the previously defined enterprise specifications, information
objects may be discovered through examination of an enterprise specification.
For example, each artefact referenced in any enterprise action in which an
ODP system participates will correspond in some way with one or more infor-
mation objects. Similarly, computational objects, interfaces and interactions
can be derived from information objects and their associated information ac-
tions.
In general, not all the elements of the enterprise specification of a system
need to correspond to elements of its information specification. For exam-
ple, not all role types in the enterprise specification correspond to object
types in the information view. Likewise, not all information objects or ac-
tions correspond to enterprise elements. One example is the decomposition of
the handset into individual parts in the information viewpoint specification;
these parts are abstracted away in the enterprise view. Similarly, the Logis-
tics Provider enterprise community and all its constituent elements correspond
to the single Courier information object type and the Branch enterprise com-
munity corresponds to the ServiceCentre information object type. In every
case, the information viewpoint complies with the policies of the enterprise
viewpoint and, likewise, all enterprise policies are consistent with the static,
dynamic and invariant schemata of the information specification.
In chapter 7, we will describe how the relationships between the elements
of two different viewpoint specifications are explicitly specified and described
in terms of correspondences. For the moment, let us simply highlight the fact
that both viewpoint specifications are views of the same system, and therefore
what is specified in one viewpoint specification about an entity needs to be
consistent with what is said about the same entity in any other viewpoint
specification. Any two views should not make mutually contradictory state-
ments; that is, they should be mutually consistent. The correspondences will
be used to check that this is so.
