Information Technology Reference
In-Depth Information
systems outside, across the wide area, are beyond our control. We often don't
even know what kind of equipment is involved, and must be satisfied with lay-
ing down minimum capabilities for things to work. Yet they are all elements
in the same conguration specication."
\But if most of the conguration is shifting sand, how about testing? We
need a firmer handle on things to test and to monitor for correct operation on
a day to day basis." Trudy paused to stare at the huge reveals, which showed
the full width of the massive walls. \Yes, the conguration detail inuences
not just where to test, but also how to test," added Trevor. \But that's why
we need to declare conformance points explicitly in the specification, so that
we will know which points we have to make accessible in an agreed way. As to
how to test, we need information from others, either implementers or deployers
of parts not directly under our control. They must provide us enough detail
to access the conformance point and understand the choices they have made
so that tests can be interpreted correctly."
\OK, Alex, I'm beginning to see now," said Trudy, \but how do we ensure
that the right information is provided?" \Well, that's part of procurement or,
internally, of direction by senior management. The first requirement is the
establishment of clear standards, which was traditionally one of the responsi-
bilities of the monarch. Long live the King!"
6.1 Linking to the Real World
Most software designers would prefer to live in an ideal world that allows
them to specify, develop and deploy their systems for any vendor platform
without any technological or cost constraints. However, we all know that
this is never the case, and the technology viewpoint addresses this problem.
In most situations, the designer needs to take into consideration the IT in-
frastructure already available in the company, their budgetary requirements
and the existing commercial policies or strategies that might force (or forbid)
the use of particular vendor technologies. For example, a particular corpo-
ration may require the use of the huge, shiny blade array that was acquired
only a couple of years ago. Given that such a large investment has just been
made, they cannot afford to buy different hardware machines or software ap-
plications not compatible with their current platform. Another company may
have a corporate policy that forces the use of open source software in all their
applications. Others may require the use of low-cost PCs for running all their
IT applications.
These requirements pose very strong constraints on the system implemen-
tation, and so, as a result, on its software architecture, the programming
languages in which applications are developed, and the way the system func-
tionality is distributed. However, such requirements do not form part of any
