Page 173 -

156 Chapter 6 Architectural design

Controller View
View
Maps User Actions Selection Renders Model
to Model Updates Requests Model Updates
Selects View Sends User Events to
User Events
Controller
Change
Notification
State State
Change Query
Model
Encapsulates Application
State
Notifies View of State
Figure 6.3 The Changes
organization of the MVC

Appleton, 2002), and so on. Architectural patterns were proposed in the 1990s under
the name ‘architectural styles’ (Shaw and Garlan, 1996), with a five-volume series of
handbooks on pattern-oriented software architecture published between 1996 and
2007 (Buschmann et al., 1996; Buschmann et al., 2007a; Buschmann et al., 2007b;
Kircher and Jain, 2004; Schmidt et al., 2000).
In this section, I introduce architectural patterns and briefly describe a selection
of architectural patterns that are commonly used in different types of systems. For
more information about patterns and their use, you should refer to 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 success-
ful in previous systems. It should include information of when it is and is not appro-
priate to use that pattern, and the pattern’s strengths and weaknesses.
For example, Figure 6.2 describes the well-known Model-View-Controller pattern.
This pattern is the basis of interaction management in many web-based systems. The
stylized pattern description includes the pattern name, a brief description (with an
associated graphical model), and an example of the type of system where the pattern
is used (again, perhaps with a graphical model). You should also include information
about when the pattern should be used and its advantages and disadvantages.
Graphical models of the architecture associated with the MVC pattern are shown in
Figures 6.3 and 6.4. These present the architecture from different views—Figure 6.3
is a conceptual view and Figure 6.4 shows a possible run-time architecture when this
pattern is used for interaction management in a web-based system.
In a short section of a general chapter, it is impossible to describe all of the
generic patterns that can be used in software development. Rather, I present some
selected examples of patterns that are widely used and which capture good architec-
tural design principles. I have included some further examples of generic architec-
tural patterns on the book’s web pages.