Architectural Design
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
1
Design Concept
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provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
2
Analysis to Design
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
3
Fundamental Concepts
abstraction—data, procedure, control
refinement—elaboration of detail for all abstractions
modularity—compartmentalization of data and
function
architecture—overall structure of the software
 Structural properties
 Extra-structural properties
 Styles and patterns
procedure—the algorithms that achieve function
hiding—controlled interfaces
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
4
Data Abstraction
door
manufacturer
model number
type
swing direction
inserts
lights
type
number
weight
opening mechanism
implemented as a data structure
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5
Procedural Abstraction
open
details of enter
algorithm
implemented with a "knowledge" of the
object that is associated with enter
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6
Stepwise Refinement
open
walk to door;
reach for knob;
open door;
walk through;
close door.
repeat until door opens
turn knob clockwise;
if knob doesn't turn, then
take key out;
find correct key;
insert in lock;
endif
pull/push door
move out of way;
end repeat
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
7
Modular Design
easier to build, easier to change, easier to fix ...
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8
Modularity: Trade-offs
What is the "right" number of modules
for a specific software design?
module development cost
cost of
software
module
integration
cost
optimal number
of modules
number of modules
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
9
Architecture
“The overall structure of the software and the
ways in which that structure provides
conceptual integrity for a system.” [SHA95a]
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
10
EXECUTIVE
Fan out
Depth
MODULE A
Module X
MODULE B
MODULE C
Module Y
Module Q
MODULE D
Module R
MODULE E
MODULE F
Module M
MODULE G
Module N
Fan in
Module K
Module L
Module S
Module T
Breadth
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11
Information Hiding
module
controlled
interface
• algorithm
• data structure
• details of external interface
• resource allocation policy
clients
"secret"
a specific design decision
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
12
Why Information Hiding?
reduces the likelihood of “side effects”
limits the global impact of local design
decisions
emphasizes communication through
controlled interfaces
discourages the use of global data
leads to encapsulation—an attribute of
high quality design
results in higher quality software
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
13
Functional Independence
COHESION - the degree to which a
module performs one and only one
function.
COUPLING - the degree to which a
module is "connected" to other
modules in the system.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
14
Architectural Design
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
15
Why Architecture?
The architecture is not the operational software.
Rather, it is a representation that enables a software
engineer to:
(1) analyze the effectiveness of the design in meeting
its stated requirements,
(2) consider architectural alternatives at a stage when
making design changes is still relatively easy, and
(3) reduce the risks associated with the construction of
the software.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
16
Data Design
refine data objects and develop a set of data
abstractions
implement data object attributes as one or
more data structures
review data structures to ensure that
appropriate relationships have been
established
simplify data structures as required
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
17
Architectural Styles
Each style describes a system category that encompasses: (1) a
set of components (e.g., a database, computational modules) that
perform a function required by a system, (2) a set of connectors
that enable “communication, coordination and cooperation”
among components, (3) constraints that define how components
can be integrated to form the system, and (4) semantic models
that enable a designer to understand the overall properties of a
system by analyzing the known properties of its constituent
parts.
 Data-centered architectures
 Data flow architectures
 Call and return architectures
 Object-oriented architectures
 Layered architectures
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
18
Data-Centered Architecture
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19
Data Flow Architecture
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
20
Call and Return Architecture
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provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
21
Layered Architecture
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22
An Architectural Design Method
customer requirements
"four bedrooms, three baths,
lots of glass ..."
architectural design
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provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
23
Deriving Program
Architecture
Program
Architecture
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24
Structured Design
objective: to derive a program
architecture that is partitioned
approach:
 the DFD is mapped into a program architecture
 the PSPEC and STD are used to indicate the
content of each module
notation: structure chart
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
25
Flow Characteristics
Transform flow
Transaction
flow
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26
Transaction Flow
incoming flow
action path
T
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27
General Mapping Approach
isolate incoming and outgoing flow
boundaries; for transaction flows, isolate
the transaction center
working from the boundary outward, map
DFD transforms into corresponding modules
add control modules as required
refine the resultant program structure
using effective modularity concepts
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
28
Transform Mapping
a
b
d
e
h
g
f
i
c
j
data flow model
x1
x2
b
x4
x3
c
a
"Transform" mapping
d
e
f
g
i
h
j
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provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
29
Factoring
direction of increasing
decision making
typical "decision
making" modules
typical "worker" modules
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30
First Level Factoring
main
program
controller
input
controller
processing
controller
output
controller
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31
Second Level Mapping
main
D
C
control
B
A
A
B
C
mapping from the
flow boundary outward
D
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32
Transaction Example
fixture
servos
fixture setting
commands
operator
process
operator
commands
report
display
screen
robot control
robot
control
software
assembly
record
in reality, other
commands
would also be shown
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provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
33
Refining the Analysis Model
1. write an English language processing narrative
for the level 01 flow model
2. apply noun/verb parse to isolate processes, data
items, store and entities
3. develop level 02 and 03 flow models
4. create corresponding data dictionary entries
5. refine flow models as appropriate
... now, we're ready to begin design!
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
34
Deriving Level 1
Processing narrative for " process operator commands"
noun-verb
parse
Process operator command software reads operator commands from
the cell operator. An error message is displayed for invalid commands.
The command type is determined for valid commands and appropriate
action is taken. When fixture commands are encountered, fixture
status is analyzed and a fixture setting is output to the fixture servos.
When a report is selected, the assembly record file is read and a
report is generated and displayed on the operator display screen.
When robot control switches are selected, control values are sent to
the robot control system.
Process operator command software reads operator commands from
the cell operator. An error message is displayed for invalid commands.
The command type is determined for valid commands and appropriate
action is taken. When fixture commands are encountered, fixture
status is analyzed and a fixture setting is output to the fixture servos.
When a report is selected, the assembly record file is read and a
report is generated and displayed on the operator display screen.
When robot control switches are selected, control values are sent to
the robot control system.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
35
Level 1 Data Flow Diagram
operat or
comm ands
Error msg
f ixt ure
serv os
status
read
operat or
comm ands
v alid com mand
f ixt ure
det ermine
comm and
ty pe
control
robot
send
control
v alue
f ixt ure set ting
analy ze
f ixt ure
status
select report
generate
report
report
assembly
record
display
screen
robot
control
syst em
robot cont rol
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
36
Level 2 Data Flow Diagram
command
error msg
produce
error
msg
read
command
command
invalid command
determine
setting
read
fi xture
status
validate
command
determine
type
robot contr ol
format
setting
status
read
record
raw setting
combi ned
status
record
calcul ate
output
values
send
control
value
fi xture setting
values
format
report
report
assembly
record
star t /stop
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
37
Transaction Mapping Principles
isolate the incoming flow path
define each of the action paths by looking for
the "spokes of the wheel"
assess the flow on each action path
define the dispatch and control structure
map each action path flow individually
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
38
Transaction Mapping
e
a
f
d
b
i
t
g
h
k
l
data flow model
j
m
n
x1
Mapping
t
b
a
x3
x2
d
e
f
g
x4
h
x3.1
i
l
m
n
j
k
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
39
Isolate Flow Paths
command
error msg
produce
error
msg
read
command
command
invalid command
determine
setting
read
fi xture
status
validate
command
determine
type
robot contr ol
format
setting
status
read
record
raw setti ng
combi ned
status
record
calcul ate
output
values
send
control
value
fi xture setting
values
format
report
report
assembl y
record
star t /stop
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
40
Map the Flow Model
process
operator
commands
command
input
controller
read
command
validate
command
determine
type
produce
error
message
fixture
status
controller
report
generation
controller
send
control
value
each of the action paths must be expanded further
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
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41
Refining the Structure Chart
process
operator
commands
command
input
controller
read
command
validate
command
read
fixture
status
determine
type
produce
error
message
determine
setting
fixture
status
controller
format
setting
report
generation
controller
read
record
send
control
value
calculate
output
values
format
report
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 5/e and are
provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001
42