Back Room Front Room 2

40
ENTERPRISE INFORMATION SYSTEMS VI
representation, spectators arrive at the service
facility (going to facilities), queue there for a
while if no service point is available (Specs Queue
at Facilities), and eventually get serviced
(servicing).
Using this model fragment we can elaborate on
the way that stakeholder goals were refined through
the use of process modelling. We previously
mentioned the high-level goal ‘Minimise the time
that a customer has to wait in order to get serviced’.
The realisation of this goal for a given type of
service facility, and for a given demand, depends on
the availability of supply for that facility. Supply is
composed of two independent factors, the number of
service points and the service rate. Therefore, the
initial goal was decomposed into two
complementary (i.e. non-competing) goals:
‘Maximise the number of service points’ and
‘maximise the service rate’. These goals are more
accurate than the initial one, however they need to
be analysed further in order to become quantifiable.
2.2 Scenarios
Figure 2: Stakeholder-Defined Parameters for Catering
The generation of different scenarios concerning
each problem studied, and the simulation of these
scenarios with the help of the process models
developed, is an essential part of requirements
definition in the S 3 approach. Evidence from the use
of this approach on a number of industrial-strength
applications indicate that scenarios are an
indispensable tool for truly understanding the
implications of stakeholders in their deliberation of
requirements. For example, in the components of the
system model that deals with services (ATMs,
merchandising, catering, etc), fragment of which is
shown in Figure 1, there is a plethora of stakeholder
defined assumptions regarding demand and supply
for each service facility. Each set of parameter
instantiation gives rise to a specific behaviour. For
example, the example shown in Figure 2 is the result
of the following choices: (a) all catering outlets are
situated in a central area; (b) there are 44 catering
outlets in this area.
These two sets of parameters define the way that
support may be offered. In addition to these,
stakeholders also defined the demand for service as
shown in Figure 3. The choices available are: (a) the
possible demand for catering set at 15 percent of all
spectators and (b) the likely average response of
each catering service which is set at 2 minutes per
customer.
These 4 sets of parameters dictate the way that
strategy-service-support interact to give rise to
different system behaviours. Although in this
example the focus of stakeholders was on catering,
the interaction between requirements for catering
and requirements for all other components of the
system became highly visible. Catering for example,
does not exist in isolation. It is influenced by other
components and in turn it influences others. Other
relevant factors, such as spectators’ arrival and
departure patterns, were taken into account. The
stakeholders involved in scenario generation
investigated the range of probable values for each of