Sommerville-Software-Engineering-10ed

176 Chapter 6 ■ Architectural design
Figure 6.4 The
Model-View-Controller
(MVC) pattern
Name
Description
Example
When used
Advantages
Disadvantages
MVC (Model-View-Controller)
Separates presentation and interaction from the system data. The
system is structured into three logical components that interact with
each other. The Model component manages the system data and
associated operations on that data. The View component defines and
manages how the data is presented to the user. The Controller component
manages user interaction (e.g., key presses, mouse clicks, etc.) and
passes these interactions to the View and the Model. See Figure 6.5.
Figure 6.6 shows the architecture of a web-based application system
organized using the MVC pattern.
Used when there are multiple ways to view and interact with data.
Also used when the future requirements for interaction and
presentation of data are unknown.
Allows the data to change independently of its representation and vice
versa. Supports presentation of the same data in different ways, with
changes made in one representation shown in all of them.
May involve additional code and code complexity when the data
model and interactions are simple.
For more detailed information about patterns and their use, you should refer to the
published pattern handbooks.
You can think of an Architectural pattern as a stylized, abstract description of good
practice, which has been tried and tested in different systems and environments. So,
an Architectural pattern should describe a system organization that has been successful
in previous systems. It should include information on when it is and is not appropriate
to use that pattern, and details on the pattern’s strengths and weaknesses.
Figure 6.4 describes the well-known Model-View-Controller pattern. This pattern
is the basis of interaction management in many web-based systems and is supported
by most language frameworks. The stylized pattern description includes the pattern
Controller
Maps user actions
to model updates
Selects view
View
selection
User events
View
Renders model
Requests model updates
Sends user events to
controller
State
change
Change
notification
Model
State query
Figure 6.5 The
organization of the
Model-View-Controller
Encapsulates application
state
Notifies view of state
changes