actor, use-case diagram, use-case text, classes
Kristian Sandahl, IDA
krisa@ida.liu.se
Text
Process part
Start with use-cases, identify classes in the text, ...
Set of heuristics
Only model normal behaviour, keep diagrams simple
Result is the design model
has three components:
Representation part (notation part)
A Software Design Method:
Use-case modelling
Kristian Sandahl, IDA
krisa@ida.liu.se
(anticipatory design)
Kristian Sandahl, IDA
krisa@ida.liu.se
anticipate further developments in the design
do it (eager design)
Iterative Software development methods such
as Extreme Programming
Kristian Sandahl, IDA
krisa@ida.liu.se
divide (divide): problems into sub problems
conquer: solve sub problems (hopefully
easier)
compose (merge): compose the complete
solution from the sub solutions
Scheme
Divide et impera (from Alexander the Great)
defer it (lazy design)
The Divide and Conquer
Strategy
Kristian Sandahl, IDA
krisa@ida.liu.se
In case of a difficult design decision
Lazy or Eager Design
Kristian Sandahl, IDA
krisa@ida.liu.se
set of notations in (informal) textual, (semi-formal)
diagrammatic, or mathematic (formal) form
Process part
Design strategy
Set of heuristics
rules of thumb, adaptation rules
Result is the design model (design specification, SD)
has three components:
Representation part (notation part)
Produces the Software Design document SD
Groups into
conceptual design/architecture: tells the WHAT of the
system
technical design: Tells the HOW
Groups into
architectural design (coarse grain design)
detailed design (module design, low level design)
Is integrational
documents
Starts from the requirements specification (SRS) and
"The Design (Process) is the creative process
of transforming the problem into a solution"
[Pfleeger]
"Design produces a workable solution to a
given problem" [Budgen]
"Design is the description of a solution"
[Pfleeger]
A Software Design Method
The Ideal Design Process
The Ideal Design Process
1
Responsible
1 Kristian
2 Jens
3 Calle
Priority
Description
2 book ticket
1 pay ticket
1 print ticket
4. while not(sorted) .....
3. quickSort(sheet, rows, 3, num)
Kristian Sandahl, IDA
krisa@ida.liu.se
2. Sort Rows according to Column3 numerically
1. Sort Requirements according to Priority
Requirement
Information hiding example
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Source:
Source:Uwe
UweAßmann
Aßmann
Kristian Sandahl, IDA
A small number of items
never use more than 5 items
KISS (keep it simple stupid)
remove all superfluous things, make it fit on 1 page
Separation of concerns
different concepts should be separated out
Use hierarchies!
trees, trees, trees
Important Concepts
Kristian Sandahl, IDA
krisa@ida.liu.se
Kristian Sandahl, IDA
krisa@ida.liu.se
Understanding, at best exposes high-level
constraints of the system
Reuse, of components and high-level patterns,
there are frameworks to buy
collection of interacting components
Roles of architecture:
Kristian Sandahl, IDA
krisa@ida.liu.se
Roles of architecture (cont’d):
Construction, a partial blueprint including
major interfaces of the system
Evolution, ”the load-bearing walls” can be
depicted, cost of change estimated
Analysis, consistency checing and
conformance analysis of the system
Management, a key milestone, leads to
implementation strategies
Kristian Sandahl, IDA
krisa@ida.liu.se
Concurrent design
Better module replacability
Better software understanding
Hide design decisions within in a module
The overall organisation of the system as a
class
method
method
method
class
method
method
method
Software architecture
few
many
Parnas’ information hiding
principle
Software architecture
class
method
method
method
class
method
method
method
Coupling and cohesion
2
•handling exceptions
•selecting algorithm
•measuring variables
•selecting variables
Needs caution when:
Example: Air Condition
Good separation of concerns.
The controller maintains a set
point for a variable by changing
input to a process.
A software realisation of
an independent control system.
Process control
•Supports incremental testing
•Supports incremental approach
•Modifications can be performed
locally on one layer
•Implements information hiding
Advantages:
The design prescribes rules
and protocols for communication
between layers.
Each layer provides service
to the adjacent outside layer,
and acts as a client to the
adjacent inside layer.
Layering
Kristian Sandahl, IDA
krisa@ida.liu.se
Kristian Sandahl, IDA
krisa@ida.liu.se
•Potential performance problems
•Not always obvious how to
define layers
Disadvantages:
Kristian Sandahl, IDA
krisa@ida.liu.se
Processing
To
Need
Data
Seem
All
People
Kristian Sandahl, IDA
krisa@ida.liu.se
Generalisation of hierarchical composition
Decomposes the problem in independent units
Relations between objects are well depicted
Encapsulation support top-down design and
replacability
Polymorphism reduced function complexity
Correspondence with object-oriented ananlysis and
classes in Java, C++, C#, ...
Object-oriented design
Example: ISO OSI model
Source:
Source:Ericsson
Ericsson
•Easy to change knowledge sources
•Supports incremental development
Advantages:
Example: Military intelligence
system
A development of database repository
architecture.
Knowledge sources post data
in a common repository.
The respository processes shared
data and can invokate processes
in knowledge sources
Blackboard
•Facilitates use of formal specification
•Allows more complex architectures
concurrency, matrices
•Supports simulation
•Evolution is supported
•Reuse of filters supported
•Good system understanding
Advantages:
Examle: Unix shell commands
a > b > c ...
Processes streams of data
in independent components
called filters.
Pipes and filters
Kristian Sandahl, IDA
krisa@ida.liu.se
•Create a suitable and general
knowledge representation.
Difficulty:
Kristian Sandahl, IDA
krisa@ida.liu.se
•functions are duplicated
•glue filters are necessary
•limited to batch processing
Disadvantages:
3
0%
81,5
8
70
165
-
25%
45
6
37
263
~ 400.000
~ 45%
Kristian Sandahl, IDA
krisa@ida.liu.se
50%
32
5
28
370
~ 560.000
~ 60%
From: C. Jones, The Impact of Reusable Modules and Functions, in
Programming Productivity, Mc Graw Hill, 1986
Reuse rates
Time [m.m.]
# Developers
Costs per l.o.c. [DM]
Lines per m.m.
Savings [DM]
Savings
quality improvement
effectivity by concentration to optimizations
reliability
prolongation life time
flexibilization
Improvements in the software process
productivity
almost prototype construction
simulation of architectures
Documentation
clear system structures
Product quality
Goal: cost
reduction
size of class libraries
JDK 1.1: ca 1,650 classes
JDK 1.2: ca 4,000 classes
Other Goals
•Performance
Problem:
•Supports creation of domainspecific languages
•Allows users to express
themselves in more natural
terms.
Advantages:
Example: Simulation of
mathematical models.
Transforms pseudocode
into a instructions for a
simulator.
Interpreters
Motivation: Reuse
Kristian Sandahl, IDA
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Source:http://www.doc.ic.ac.uk/~tpg99/vs.html
Example of blackboard
datastructure
Kristian Sandahl, IDA
krisa@ida.liu.se
Kristian Sandahl, IDA
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CORBA
Kristian Sandahl, IDA
krisa@ida.liu.se
Source:
Source:
http://www.cs.wustl.edu/~schmidt/
http://www.cs.wustl.edu/~schmidt/
Kristian Sandahl, IDA
krisa@ida.liu.se
Reuse of partial solutions: instead of new solution
Easy configurability of the systems
variants, versions, product families
off the shelf, COTS)
Divide-and-conquer (Alexander the Great)
Well known in other disciplines
mechanical engineering DIN 2221
electrical engineering
architecture
Outsourcing to component producers (components
Motivation for Component
Based Development
4
C5=0.12
shaf tS1=2e-3
S
bearing1
S
planetary2=110/50
demultiplex
shaftS=2e-3
planetary1=110/50
bearing4
C8=0.12
C4=0.12
bearing2
C6=0.12
Kristian Sandahl, IDA
krisa@ida.liu.se
Can go really wrong!
Creative and fun.
Can be used for other
purposes too.
Increase comprehension,
reduce learing period.
Often used in graphical
user interface (GUI) design.
planetary3=120/44
C11=0.12
Kristian Sandahl, IDA
krisa@ida.liu.se
qRef
qdRef
-
pSum
A1
C1
R2
Op1
Op2
R3
R4
Op3
Op5
+1
+1
sum
-
w Sum
tacho2
b(s)
a(s)
a(s)
qd
PT1
tacho1
Rd2=100
S
340.8
b(s)
a(s)
r ate3
iRef
-
g5
g4
-
Rp1=200
Jmotor=J
cut joint
C=0.004*D/w m
1
r3Drive1
Ri=10
r3Motor
Rd1=100
r3Control
rate2
i
k1
i
b(s)
S
S
k2
rate1
1
1
q: angle
qRef
qdRef
r el
S
spring=c
qd
q
tn
g2
qd
r
gear=i
S
joint=0
axis1
axis2
axis3
axis4
axis5
axis6
y
x
inertial
Final
system
Kristian Sandahl, IDA
krisa@ida.liu.se
Kristian Sandahl, IDA
krisa@ida.liu.se
Hierarchical Composition of a Modelica Model of an
Industrial Robot
C3
C2
Vs
+
+
Srel = n*n' + (identity(3) - n*n')*cos(q)
- skew(n)*sin(q);
diff
+
pow er
OpI
wrela = n*qd;
zrela = n*qdd;
Rd4=100
emf
Sb = Sa*Srel';
r0b = r0a;
g3
vb = Srel*va;
g1
wb = Srel*(wa + wrela);
ab = Srel*aa;
hall1
w
zb = Srel*(za + zrela + cross(wa, wrela));
fa = Srel'*fb;
ta = Srel'*tb;
q
0.3
Kv
0.03
Kd
qddRef
R1
Integrational Software Engineering
Rd3=100
Rp2=50
Modelica Visual Programming:
Decomposition and Abstraction of an Automatic Gearbox
C12=0.12
fr ic=Rv0
Metaphors
Ra=250 La=(250/(2*D*w m))
hall2
Equations and mathematical functions allow acausal modeling, high
level specification, increased correctness
Combine electrical, mechanical, thermodynamic, hydraulic, biological,
control, event, real-time, etc...
Strongly typed object-oriented language with a general class concept,
Java & Matlab like syntax
Hierarchical system architecture capabilities
Kristian Sandahl, IDA
krisa@ida.liu.se
1000 clients asking for 1 Mbit transactions
every 4th minute
Estimate the bandwidth required to serve
Describe a system architecture
Kristian Sandahl, IDA
krisa@ida.liu.se
Efficiency comparable to C; advanced equation compilation, e.g. 300
000 equations, ~150 000 lines on standard PC
Exercise
Efficient, non-proprietary
Visual component programming
Everything is a class
Multi-domain modeling
Declarative language
Modelica – the Next Generation
Computational Modeling Language
5