Information Technology Reference
In-Depth Information
objects will be used to define the ways in which the user communicates with the
system in order to make his or her request, and the ways in which the system
responds directly back to the user.
Control Objects are used to model the internal workings of the software
system itself. That is, they represent the complex algorithms and computations
used to process information and perform actions (Schach
2008
). Control objects
are the means by which use cases are fully realized from start to finish. They
handle all of the activity that the system is responsible for carrying out.
6.4 Scenario-Based Modeling
In computing, a scenario is a narrative describing foreseeable interactions by
various types of users (characters) and the system. Scenarios include information
about goals, expectations, motivations, actions and reactions. Scenarios are neither
predictions nor forecasts, but rather attempts to reflect on or portray the way in
which a system is used in the context of daily activity. Scenarios are frequently
used as a part of the system's development process. They are typically produced
by usability or marketing specialists, often working in harmony with end users and
developers. Scenarios are written in plain language, with minimal technical details,
so that stakeholders (designers, usability specialists, programmers, engineers,
managers, marketing specialists, etc.) have a common example for which they can
focus their discussions. Increasingly, scenarios are used directly to define the
wanted behavior of software; replacing or supplementing traditional Functional
requirements. In the agile style of software development, scenarios are written as
brief user stories. In the more deliberate style of software development, scenarios
are written as structured use cases.
Scenarios can be used in various ways. First, they can be used as vision pieces.
Vision pieces provide a high level picture of an envisioned system or product.
They can also be used to focus on the value offered by a system, showing how it
offers an advantage over the way things are. This type of scenario may be used to
'sell' an idea within the organization that is considering developing the system.
Use-oriented techniques are widely used in software requirement analysis and
design. Use cases and usage scenarios facilitate better system understanding and
provide a common language for communication. In this model, scenarios are
organized hierarchically and they capture the system functionality at various
abstraction levels including scenario groups, scenarios, and sub-scenarios. Com-
bining scenarios or sub-scenarios can form complex scenarios. Data are also
separately identified, organized, and attached to scenarios. This scenario model
can be used to cross-check the UML model. It can also direct systematic scenario-
based testing including test case generation, test coverage analysis with respect to
requirements, and functional regression testing.
