Information Technology Reference
In-Depth Information
never send a message unless the recipient is already able to interpret it. It's
called the no surprises rule, and is the key to the management of distributed
upgrades. You always upgrade the receiver before the sender, and only let
your clients make requests the server is able to satisfy.
We always need to
keep the principle in mind."
\Any more words of wisdom, Alex?" \I think that just about covers it;
now you just need to put it into practice. Always have the next bottle open
before the guests need it; I'd like some more of your ne Sancerre."
13.1 Coping with Change
No organization remains unchanged, and so business processes and infras-
tructure requirements are continually evolving. The ODP architecture tries
to limit the impact of technical innovation to be within the engineering and
technology viewpoints, and this can be done as long as the basic functional-
ity provided to the organization remains the same. However, new technology
enables new ways of doing business, and so technology can be a stimulus for
business process reengineering.
More crucially, however, there are continual new opportunities for business
innovation, arising from the opening up of new markets, mergers or acquisi-
tions, and internal organizational changes. These all lead to changes in the
IT requirements, and are generally more pressing than the cycle of technology
adoption. No manager will willingly accept being told that they must wait for
IT changes before entering a new and potentially lucrative market.
The RM-ODP does not have a lot to say directly about such unforeseen
changes (as opposed to its provision of policies at predictable variation points,
as described in chapter 10) because it describes systems as they exist, not the
dynamics of the process by which they are developed. However, the reference
model is structured to make evolution easy; this is a result of the separation
of concerns it offers to the various stakeholders. Separating the system speci-
fication into a set of viewpoints, loosely coupled in a clearly understood way
by explicit correspondences, allows various aspects of evolution to be carried
out separately, as long as overall consistency is maintained.
13.2 The Importance of Tool Support
One of the problems with business-driven evolution is that it is dicult to
predict how pervasive the impact of a given change will be. Technology-driven
change usually involves the modification of the way some concept representing
