Ivica Crnkovic
Mälardalen University
Department of Computer Science and Engineering
ivica.crnkovic@mdh.se
http://www.idt.mdh.se/~icc
Software engineering and Scientific Methods
Page 1, 10/21/2008
Contents
‰ What
Wh t is
i Software
S ft
Engineering?
E i
i ?
‰ Software Engineering and Science
‰ Methods
M th d off Software
S ft
Engineering
E i
i
‰ Software Engineering Research
‰ Example
E
l – Software
S ft
architecture
hit t
Software engineering and Scientific Methods
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What is Software Engineering?
‰ Software engineering is an engineering discipline which is
concerned with all aspects of software production from the
early stages of system specification through to maintaining
the system after gone into use.
Ian Sommerville, Software Engineering
‰ We need further explanation of:
z
Engineering discipline
z
All aspects of software production
Software engineering and Scientific Methods
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Engineering
Engineers make the things work
‰ Solving
g problems
p
‰ understand the problem
‰ analyze
y the p
problem
‰ Find solutions
‰ Constructing
g the solution from p
parts that address the p
problem's
various aspects - do a synthesis
‰ To achieve the goal engineers
‰ apply theories, methods and tools from different disciplines
‰ Search for solutions even when there is not theory or methods
Software engineering and Scientific Methods
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Analysis of a problem
PROBLEM
Identify different aspects of the problem
Arrange the problems in clearly defined and
understandable sub-problems
Subproblem 1
Subproblem 2
Subproblem 3
Software engineering and Scientific Methods
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The synthesis
Find solutions for subproblems
Sol tion 1
Solution
Sol tion 2
Solution
Solution 3
S l i 4
Solution
Put together solutions to a consistent view
Provide (make) a solution
SOLUTION
Software engineering and Scientific Methods
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Engineering Example – the Vasa Ship
A master piece of work!
‰ 1625 King Gustav II Adolf decided to start build
Wasa
‰ 1628 - maiden voyage
voyage.
Length- 69 metres
LengthMaximum width - 11.7 metres
From keel to the top of the main mast - 52.5 metres
Height of the stern - 19.3 metres
Crew: 445 men
men, Seamen – 145
145,, Soldiers - 300
Armament 64 guns
Thousands of people involved in the project
Selecting wood, building different parts
g food,, other services
Providing
Software engineering and Scientific Methods
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WHat happen with the Vasa ship?
Software engineering and Scientific Methods
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Vasa – Example of Bad Engineering
‰ the ship capsized on her maiden
voyage in the harbor of Stockholm.
Why did the Vasa capsize?
Software engineering and Scientific Methods
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Why
y did the Vasa capsize?
p
‰ The
Th V
Vasa capsized
i d because
b
it was nott stable;
t bl
‰ The Vasa capsized because
z
th methods
the
th d ffor calculating
l l ti stability
t bilit were now kknown
)or
z
the building process (or in terms of software engineering
engineering, the
development project) was inadequate.
Software engineering and Scientific Methods
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How to calculate stability?
Gravity
y force
Ship weight
Buoyancy
(bärkraft)
Ship’s center of gravity
Center of buoyancy
(water) displacement
The forces are of equal size and in the opposite directions
Software engineering and Scientific Methods
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The ship heels at an angle
h
Ship’s center of gravity
Software engineering and Scientific Methods
h – leverage effect
( åt k i )
(påtryckning)
Center of buoyancy
(water displacement)
Has moved right
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Leverage effect (Moment)
Torque is defined as the product
of radius, force, and the sine of the
angle between force and radius:
t = r F (sin(X))
X
http://members.aol.com/PhysicsDad/calcphys/lecture.html
Software engineering and Scientific Methods
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The ship heels at an angle
h – leverage effect
( åt k i )
(påtryckning)
This
s Torque
o que (Moment)
( o e t)
will force the
Ship to return back
h
Software engineering and Scientific Methods
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The ship is unstable
h – leverage effect
(påtryckning)
Torque has change the direction
The ship will capsized
h
h
Software engineering and Scientific Methods
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The ship is stable
If the center of gravity is very low – the ship will be stable
h
Software engineering and Scientific Methods
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h
Why the ships heel?
Because of wind!
Or waves…
h
Software engineering and Scientific Methods
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Stability
y Curve
Torque
Result = S - W
Wind (opposite direction)
A
S2
B
S1
αΑ
α1
αΒ α2
Software engineering and Scientific Methods
α
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Why did Vasa capsize?
‰ It was nott stable
t bl
z
At that time there was no formal modeling for calculating
stability
‰ But at that time there were many ships which did not
capsized!
Software engineering and Scientific Methods
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Why did Vasa capsize?
‰ Engineering
E i
i
–
z
Solve problems even when there is no formal theory
z
Experience – best practices
z
Ob
Observations
ti
z
Rules of thumb
z
P
Processes
to
t ensure the
th ffeasibility
ibilit off problem
bl
solving
l i
z
COULD VASA BE SUCSSESFULLY BUILT IN SPITE OF
LACK OF THEORY?
z
WHAT DID PROJECT FAILED TO DO?
Software engineering and Scientific Methods
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Other reasons why Vasa capsized?
‰ Resource & budget plan. The project was delayed and in its
later phases, there was enormous pressure to finish work on
time.
ti
‰ Project management.
management The main builder (or in modern terms,
terms
the project manager) unfortunately sickened and died during
the building of the ship, and the consequence was weak
managementt and
d very poor coordination
di ti
off the
th groups
building different parts.
‰ Changes in requirements. The original requirement for one
gun deck was changed to two gun decks when the building
of the ship had already begun. Because the king was behind
the decision, its possible consequences were not analyzed.
Software engineering and Scientific Methods
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Other reasons why Vasa capsized?
‰ Conflicting requirements and trade-off analysis. The Vasa
was intended to be a new type of ship combining superior
sailing
ili
characteristics
h
t i ti and
d maneuverability
bilit with
ith
overwhelming striking force.
‰ Design changes during the construction. The dimensions of
the ship were changed several times during its construction
with
ith no proper analysis
l i off the
th consequences.
‰S
Scalability.
l bilit Vasa
V
was designed
d i
d as a smaller
ll ship,
hi and
d its
it
dimensions were merely proportionally increased.
‰ Validation. The stability and other tests were primitive and
not well performed. (Test: running across the deck)
Software engineering and Scientific Methods
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Vasa Disaster – Similar do Software Projects
Si il situation
Similar
i
i
in
i software
f
development
d
l
project
j
‰ No formal/theoretical background for requirements and
solution
‰ Feasibility of the requirements not analyzed
‰ Changes in requirements during the project work
‰ Time and Budget not properly planned
‰ No proper verification/validation
‰ Bad quality assurance
‰ Shortage in knowledge in new disciplines
....
Software engineering and Scientific Methods
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Engineering vs. Software Engineering
‰ Many similarities
‰ Methods and procedures
‰ Similar objectives and goals
‰ Many differences
‰ Difference between software and hardware/the real world
‰Software – no physical limits
‰Not visible
‰Modifiable
‰More complex
‰ Different theories and methods used
‰ Different experiences
experiences, traditions
‰ Different maturity level
Software engineering and Scientific Methods
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All aspects of Software Development
‰ Aspects
A
t
z
Technical (how technically solve the problem)
z
O
Organizational
i ti
l (h
(how tto organize
i people)
l )
z
Financial
z
M k ti
Marketing
z
Professional and ethical responsibility
z
R
Research
h and
dS
Science
i
Software engineering and Scientific Methods
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Example – distributed software development
‰ Developing
D
l i
software
ft
on different
diff
t locations
l
ti
z
Advantages: ….
z
Di d
Disadvantages….
t
z
Diff
Different
t ttechniques,
h i
diff
differentt processes, different
diff
t people
l
Software engineering and Scientific Methods
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How to break the barriers?
Teachers
teachers
Common Course
Common projects
Students
Students
Video Conference
Web Cameras
Chat - Messengers
Mail
Web
Database
Software engineering and Scientific Methods
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Computer Science Vs. Software Engineering
COMPUTER SCIENCE
Computer Functions
OTHER SCIENCES
Theories
CUSTOMER
Problem
SOFTWARE ENGINEERING
Software Engineering
Research & Science
Principles, Methods
and Tools to Solve
Problem and
Construct sSolutions
Software engineering and Scientific Methods
Solution
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Computer Science Vs. Software Engineering
COMPUTER SCIENCE
Algorithms and data structures
Programming languages
Architecture
Numerical and symbolic computation
Operating systems
SOFTWARE
ENGINEERING
Software methodology and engineering
Databases and information retrieval
Artificial intelligence and robotics
Human computer communication
Human-computer
In many cases a defuse
Social, ethical, and professional issues
boundaries between SE and CS
Software engineering and Scientific Methods
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Methods and Technologies
Solution
Phases
Requirements
Analysis
Design
Implementation
Test
Delivery
Maintenance
Service
Software/Systems Engineering Methods
Different
e e t Technologies
ec o og es
Software engineering and Scientific Methods
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SE disciplines and areas
From European Software Engineering Conference and
Symposium on the Foundations of Software Engineering
‰ Req
Requirements
irements Engineering
‰ Specification and Verification
‰ Software Architecture and
Design
‰ Analysis and Testing
‰ Development Paradigms and
Software Processes
‰ Evolution and Refactoring
‰ Tools and Environments
‰ Empirical Software
Engineering
‰ Software Metrics
‰ Software Quality and
Performance
‰ Component
Component-based
based Software
Soft are
Engineering
‰ Model Driven Engineering
‰ Web Applications
‰ Distributed Systems and
Middleware
‰ Service Oriented Applications
‰ Mobile and Embedded System
‰ Open
O
Standards
S
and
Certification
‰ Software Economics and
H
Human
R
Resources
‰ Dependability (safety, security,
reliability)
‰ Case Studies and Experience
Software engineering and Scientific
Methods
Reports
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SE disciplines - more examples
‰ Project management
‰ Real-time
‰ Development processes
‰ Tools and environments
‰ Reverse engineering
‰ Software Configuration
Management
‰ Software Maintenance
‰ Object-oriented
Object oriented modelling
‰ Formal specification
‰ Software dependability
(reliability, safety,…)
So t a e e
engineering
g ee g a
and
d tthe
e
‰ Software
Internet
‰ Education
‰ Software Economics
‰ ......
Software engineering and Scientific Methods
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Software Engineering Methods - Examples
Requirements
Analysis
Design
Implementation
Test
Delivery
Maintenance
Service
Project Management
Software Development Models and Processes support
Component based Software Engineering (CBSE)
Component-based
Requirements Engineering
Analyse/design
y
g methods (UML,
(
OOP, Formal methods, ...))
Architectural analysis (tradeoff analysis, quality, attributes…)
Programming Methods /Languages
Configuration Management
Test and Verification
Customer support, Maintenance
Software engineering and Scientific Methods
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What is then Software Engineering Research?
‰ Analyzing natures of problems and their solutions
‰ Finding more general principles that SE can use
‰ Developing methods and tools
‰ Implementing principles on new problem domains
‰ ……
Software engineering and Scientific Methods
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Software Engineering Research
‰Different methods used SE
‰Exemplified by Software Architecture
z
Presentation extracted from Mary Shaw
Shaw’s
s
presentation on ICSE 2001 in Toronto
http://www-2
http://www
2.cs.cmu.edu/
cs cmu edu/~Compose/paper
Compose/paper_abstracts/etaps
abstracts/etaps-2002
2002.html
html
Software engineering and Scientific Methods
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The basic characteristic of SE
REAL WORLD
Practical problem
?
REAL WORLD
Practical Solution
Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Research Strategy
gy
Software engineering and Scientific Methods
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Validation of the Result
Software engineering and Scientific Methods
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Nasreddin story and Software Engineering
Story about a lost ring
N
Nasreddin
ddi Hodja
H dj
Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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SE Research process
‰ Research
R
hQ
Questions
ti
‰ Research Results
‰ Result Validation
Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Example: Software Architecture
‰ The software architecture of a program or computing system
is the structure or structures of the system,
y
, which comprise
p
software components, the externally visible properties of
those components and the relationships among them
L. Bass,
L
B
P.
P Cl
Clements, R
R. K
Kazman, Software
S ft
Architecture
A hit t
In
I Practise,
P ti
Addi
Addison
Wesley, 1998
System
S
Subsystem
subsystem
component
component
Software engineering and Scientific Methods
component
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Research Model – different phases in research life cycle
Software engineering and Scientific Methods
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Example:Software architecture
New concept:
p system
y
decomposition
p
System
subsystem
component
S b
Subsystem
t
component
Software engineering and Scientific Methods
component
Page 63, 10/21/2008
Next step – Characterisation - Architectural Style
‹
Recurring structures that occur in software systems
AS = {Component types,Connector types,Constraints}
Component
and Connector
Types
Pipe and Filter
Shared Repository
Layered Abstract Machines
Buss
Software engineering and Scientific Methods
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Next step: Aspects of Software Architecture
‹ Further
characterisation Elements and Form
Attachment
Connector
Arch Component
Port
Representation
Role
(sub)System
‹ Rationale
¾ Describes how the architecture satisfies system requirements for both
functional and extra-functional properties.
Software engineering and Scientific Methods
Page 65, 10/21/2008
Next step: Formalization
Example
p - UML
IComA
<<subsystem>>
ComA
IComB
<<subsystem>>
ComB
Conceptual
Architecture
IComA
<<subsystem>>
ComC
Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Software engineering and Scientific Methods
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Summary
‰ Software
S f
E
Engineering
i
i is
i oriented
i
d on practical
i l things
hi
from the real word
z
Understanding problems, providing software
f
solutions
‰ SE uses methods and tools for solving the problems
from different disciplines
‰ SE research
z
Understanding principles
z
Defining principle for solving the problems
z
Developing methods and tools
Software engineering and Scientific Methods
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