Information Technology Reference
In-Depth Information
For example, an information exchange service component may be obtained
to integrate information provided by a group of contributing peers. From the
point of view of providing this service, it is the coordinating activity which will
form the focus of its enterprise specification; the objective is to generate and
distribute a common shared image from information contributed by members
of a group. Why they should wish to do this is not of any concern to the
component provider.
Associated with this view of the product, there will then be a set of shared
data types in an information view, a computational access procedure, and
supporting engineering and technology constraints.
Such a component could be used in many ways. In coordinating a com-
mittee, or a project group, the information exchange is a specific kind of
interaction between the community roles being specified, and the service for
doing so is therefore visible in the enterprise specification; however, the exact
way the service is accessed forms part of the computational specification. On
the other hand, in a survey application, the coordination may be implicit,
expressed via requirements on one particular role to provide statistical in-
formation, but without reference to the enabling service until the detailing
of the computational specification. Finally, if a scientific modelling activity
needs to exploit distributed simulation tools, the same coordination compo-
nent might be used as a collation mechanism in the engineering viewpoint but
be completely invisible in the computational design.
To achieve this, the viewpoints of the component and the user applica-
tions are related in different ways, but retain their independence. A practical
example of this can be seen in the standardization of the ODP trader func-
tion (ISO/IEC 13235-1), a general-purpose service publication and resource
discovery mechanism [9]. This standard describes enterprise, information and
computational specifications of trading, but leaves the engineering specifi-
cation to a platform designer (although one specific engineering realization,
supporting the use of directories, is standardized in ISO/IEC 13235-3 [10]).
The trader function is visible in application designs only in their computa-
tional view as a service accessed by well-known interfaces, and in the definition
of selected information data types and constraints. This reflects the difference
between the stakeholders involved in an organization that uses a service and
the organization that provides it.
12.3.2
Changing Technologies
As a product evolves, it acquires new features and exploits new supporting
services. The supplier maintains upwards compatibility if no service is with-
drawn and no additional demands are made on the infrastructure. At each
step in the evolution, there is a corresponding set of models describing capa-
bilities and requirements. In practice, many vendors offer a more restrictive
guarantee of compatibility, in which, at every release, a statement is made
about how many steps back down the release chain the compatibility relation-
