Software engineering lecture notes

Software engineering lecture notes in Software engineering uploaded at P.R.Engineering college

Software engineering lecture notes in Software engineering at P.R.Engineering college uploaded by P.R.Engineering college Staff in lecturenotes.net

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CS6404
 
SOFTWARE ENGINEERING

UNIT I

SOFTWARE PRODUCT AND PROCESS

Software engineering paradigm:
• The framework activities will always be applied on every project ... BUT the tasks (and degree of rigor) for each activity will vary based on:
– the type of project
– characteristics of the project
– common sense judgment; concurrence of the project team
The software process:
• A structured set of activities required to develop a software system
– Specification;
– Design;
– Validation;
– Evolution.
 
• A  software
 
process
 
model  is
 
an  abstract
 
representation  of  a
 
process.
 
It  presents  a
 
description of a process from some particular perspective.
Waterfall model/Linear Sequential Model/classic life cycle :

• Systems Engineering
 
– Software
 
as part of larger system, determine requirements for all system elements, allocate requirements to software.
 
• Software Requirements Analysis
 
– Develop understanding of problem domain, user needs, interfaces, ...
– Software Design
 
function, performance,
 
– Multi-step
 
process to determine architecture, interfaces, data structures,

• Coding
–
 
functional detail. Produces (high-level) form that can be checked for quality, conformance before coding.

Produce machine readable and executable form, match HW, OS and design needs.
 
•  Testing

– Confirm that components, subsystems and complete products meet requirements, specifications and quality, find and fix defects.
• Maintenance
 
– Incrementally,
 
evolve
 
software  to
 
fix
 
defects,
 
add
 
features,
 
adapt  to
 
new
 
condition. Often 80% of effort spent here!
Waterfall model phases:
• Requirements analysis and definition
• System and software design
• Implementation and unit testing
• Integration and system testing
• Operation and maintenance
• The main drawback of the waterfall model is the difficult y of accommodating change
after the process is underway. One phase has to be complete before moving onto the next phase.
• Each phase terminates only when the documents are complete and approved by the SQA
group.
• Maintenance begins when the client reports an error after having accepted the product. It could also begin due to a change in requirements after the client has accepted the product
Waterfall model: Advantages:
• Disciplined approach
• Careful checking by the Software Quality Assurance Group at the end of each phase.
• Testing in each phase.
• Documentation available at the end of each phase.
Waterfall model problems:
• It is difficult to respond to changing customer requirements.
• Therefore, this model is only appropriate when the requirements are well-understood and changes will be fairly limited during the design process.
• Few business systems have stable requirements.
• The waterfall model is mostly used for large systems engineering projects where a system is developed at several sites.
• The customer must have patience. A working version of the program will not be available until late in the project time-span
• Feedback from one phase to another might be too late and hence expensive.
The Prototyping Models:
• Often, a customer defines a set of general objectives for software but does not identify detailed input, processing, or output requirements.
 
• In
 
other
 
cases,
 
the
 
developer
 
may
 
be unsure
 
of the
 
efficiency of an  algorithm,
 
the
 
adaptability of an operating system, or the form that human –machine interaction should take
• In this case prototyping paradigm may offer the best approach
• Requirements gathering
• Quick design
• Prototype building
• Prototype evaluation by customers
• Prototype may be refined

• Prototype thrown away and software developed using formal process{ it is used to define the requirement} Prototyping
 
Strengths:
•
•
•
•

Requirements can be set earlier and more reliably
Customer sees results very quickly.
Customer is educated in what is possible helping to refine requirements.
Requirements can be communicated more clearly and completely
 
• Between
 
developers
 
and
 
clients
 
Requirements
 
and
 
design  options
 
can  be

Weaknesses:
 
investigated quickly and Cheaply
 
– Requires  a
 
rapid
 
prototyping
 
tool  and
 
expertise
 
in  using
 
it–a  cost
 
for  the
 
development organisation
– Smoke and mirrors - looks like a working version, but it is not.
The RAD Model:
 
• Rapid
 
Application
 
Development
 
is a
 
linear
 
sequential
 
software
 
development
 
process
 
model that emphasizes an extremely short development cycle
• Rapid application achieved by using a component based construction approach
• If requirements are well understood and project scope is constrained the RAD process enables a development team to create a ―fully functional systemǁ
Team # n

M o d e lin g bus ines s   m odeling  d at a   m
odelin g
proc es s    m odeling

Communicat ion

Planning

Team # 2

Mo d el i ng
b u si n e ss m o d e li n g d a t a m o d eli n g
p ro ce ss m o d eli n g
 
C o n s t ru c t io n
c   om p on en t   r e us e aut om at ic   c od e
gen er at ion t es t ing

Team # 1

Mode ling b u si ne ss mo d e l in g d at a mo d e li n g
p ro ce ss mo d e l i ng
 
Co nst r uct i o n co m p o n e n t re u se a u t om a t i c cod e
g e n e ra t i o n t e st i ng
 
De ployme nt int e grat ion de liv e ry
f eed b ack

Const r uct ion co mp o n e n t reuse aut omat ic co d e
g e n e rat i o n
t est ing

6 0 - 9 0 d ays

RAD phases :
• Business modeling
• Data modeling
• Process modeling

• Application generation
• Testing and turnover
Business modeling:
• What information drives the business process?
• What information is generated?
• Who generates it?
Data Modeling:
• The information flow defined as part of the business modeling phase is refined into a set of data objects that are needed to support the business.
 
• The characteristics
 
( called attributes) of each object are identified and the relationships
 
between these objects are defined
Process modeling:
• The data modeling phase are transformed to achieve the information flow necessary to implement a business function.
• Processing descriptions are created for adding , modifying, deleting, or retrieving a data object
Application generation:
• RAD assumes the use of 4 generation techniques.
• Rather than creating software using conventional 3 generation programming languages,
the RAD process works to reuse existing program components (when possible) or created reusable components (when necessary)
Testing and Turnover:
• Since the RAD process emphasizes reuse, many of the program components have already been testing.
• This reduces over all testing time.
• However, new components must be tested and all interfaces must be fully exercised
Advantages &Disadvantages of RAD: Advantages
• Extremely short development time.
• Uses component-based construction and emphasises reuse and code generation
Disadvantages
• Large human resource requirements (to create all of the teams).
 
• Requires activities.
 
strong
 
commitment
 
between
 
developers
 
and
 
customers
 
for
 
“rapid-fire”
 
• High performance requirements maybe can’t be met (requires tuning the components).
The Incremental Model

incr em ent  # n

C                  o    m              m              u      n     i     c               a               t          i     o     n
P                     l     a               n     n     i     n     g
M                         o      d     e               l      i    n      g
 
a n a l y s i s
 
C                  o  n   s  t    r  u   c  t i   o   n
 
d e s i g n
 
D   e   p  l  o  y   m   e   n   t
 
c o d e
 
t e s t
 
d  e   l       i         v      e   r y
 
f                    e               e               d     b     a               c               k

incr em ent  #  2

C    o     m               m               u  n   i    c              a             t         i     o     n
P                     l     a               n     n     i     n     g
M                         o     d     e               l     i     n     g
a       n a l ys is

C                     o     n      s              t          r    u     c              t          i     o     n

d     e l i ve r y    of
n   t h   in cr em e nt

incr em ent  # 1
 
d        e s i g n
 
c o d e t e s t
 
D   e   p  l  o   y   m    e   n  t d   e   l  i  v   e   r y
f  e   e   d   b   a   c   k
 
d     e li ve r y    of
2     n d     incr e m e nt

C     o   m    m              u    n     i  c   a              t         i     o    n
P                    l  a   n  n i   n   g
M    o  d  e   l        i          n     g
 
a n a l y s i s
 
C                     o     n     s               t          r    u     c              t          i     o     n
 
d        e s i g n
 
c o d e  D  e  p  l  o  y  m   e    n   t
t  e s  t  d  e  l       i         v      e   r  y
f  e   e   d    b   a   c   k
 
d     e l i ve r y    of
1    st   incr e me  nt

pr oj ect  calen d ar t im e :

The Incremental development
• Combination of linear + prototype
 
• Rather
 
than
 
deliver
 
the
 
system as a
 
single
 
delivery,
 
the
 
development
 
and
 
delivery is
 
broken
 
down
 
into
 
increments
 
with
 
each
 
increment
 
delivering
 
part  of
 
the
 
required
 
functionality
• User requirements are prioritised and the highest priority requirements are included in early increments
• Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve
Incremental development advantages:
 
• The
 
customer is able to do some useful work after release
 
• Lower risk of overall project failure
• The highest priority system services

tend to receive the most testing
 
Spiral Model:

Title:
Software engineering lecture notes

Subject:
Software engineering

Institute:
P.R.Engineering college

Software engineering lecture notes

Software engineering lecture notes in Software engineering uploaded at P.R.Engineering college

Summary / document preview text:

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