Information Technology Reference
In-Depth Information
Chapter 4
Computational Viewpoint
Claire looked across at Ira as he bent over his laptop, navigating through
the information model to find the diagram dealing with phone properties. She
had seen him around the oce, of course, but this was the first time she had
worked with him directly. He was tanned with fair hair and was dressed in
a slightly formal ranch style with a strongly patterned shirt and had a self-
confident, but rather reserved air. He certainly seemed to have picked up the
ideas quickly enough, and his modelling background was strong, but he didn't
seem so familiar with implementations.
\Here it is," he said, switching the diagram to the projector. \You can see
that the definition here breaks down into owner and organizational properties
on this side, and hardware structure and replaceable units over on the other
side. We can derive the different specializations you have been talking about
from this." \OK, but there are items in our design that are not here." \Sure,
that's ne. There are bound to be elements describing the process details
that would only be of local interest. I would expect your model to import a
selective view of this, and then extend it to include new material." He traced
one subtree of the diagram. \Here is the structure concerned with the SIM and
its properties. Suppose we want to order a replacement for a faulty SIM. That
requires a message containing the SIM's description, which means transferring
an object of this SIM type, with fields to give the required capacity. You just
have to pick an encoding for it."
\Not me," laughed Claire; \that's Nigel's problem, not mine. The models
I'm building are platform independent, because we want them to be valid
across a lot of dierent technologies. My group really shouldn't be concerned
with the engineering detail." \Hang on, though," Ira said, \if we want to hide
the engineering detail, why am I being asked to describe SIMs?" Claire smiled.
\But your description is of the phone as a business object, which we need to
repair, not as part of our infrastructure that supports the business. Unless
you are a network operator, you should try to keep the two topics separate."
\And if I were a network operator?" asked Ira. \Well, then you would
be using the network, which is your main product, to manage itself, and the
same network components are both business objects and part of the supporting
infrastructure. You would still try to compartmentalize these roles, though."
Ira loosened the top of the coee ask. \OK then, Claire, how do we know
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