Explain the following with
the help of an example
(i)
Common coupling
(ii)
Communicational cohesion
(iii)
Class diagram
(iv)
Structure chart
1.
Common coupling: Common coupling is when two modules share
the same global data (e.g. a global variable). Changing the shared resource
implies changing all the modules using it. Diagnosing problems in structures
with considerable common coupling is time consuming and difficult. However,
this does not mean that the use of global data is necessarily”bad”. It does not
mean that a software designer must be aware of potential consequences of common
coupling and take special care to guard against them.
2.
Communicational cohesion: Communicational cohesion is when parts
of a module are grouped because they operate on the same data (e.g. a module
which operates on the same record of information). In this all of the elements
of a component operate on the same input data or produce the same output data.
So we can say if a module performs a series of actions related be a sequence of
steps to be followed by the product and all actions to be performed on the same
data.
3.
Class diagram: A class diagram in the Unified Modeling
Language (UML) is a type of static structure diagram that describes the
structure of a system by showing the system's classes, their attributes, and
the relationships between the classes. The UML specifies two types of scope for
members: instance and classifier. In the case of instance members, the scope is
a specific instance. For attributes, it means that its value can vary between
instances. For methods, it means that its invocation affects the instance
state, in other words, affects the instance attributes. Otherwise, in the
classifier member, the scope is the class. For attributes, it means that its
value is equal for all instances. For methods, it means that its invocation do
not affect the instance state. Classifier members are commonly recognized as
"static" in many programming languages.
4.
Structure chart: A structure chart is a top-down modular
design tool, constructed of squares representing the different modules in the
system, and lines that connect them. The lines represent the connection and or
ownership between activities and sub activities as they are used in
organization charts.
In structured analysis
structure charts are used to specify the high-level design, or architecture, of
a computer program. As a design tool, they help the programmer in dividing and
conquering a large software problem, that is, recursively breaking a problem
down into parts that are small enough to be understood by a human brain. A
structure chart depicts
• The size and complexity of
the system.
• Number of readily
identifiable functions and modules within each function.
• Whether each identifiable
function is a manageable entity or should be broken down into smaller
components.
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