INTRODUCTION TO
SOFTWARE ENGINEERING
Citra Noviyasari, S.Si, MT
1 Rekayasa Perangkat Lunak - Citra N., S.Si,
What is software ?
Software is a set of items or objects
that form a “configuration” that
includes
• programs
• documents
What is software?
Definitions:
Computer programs, procedures, and possibly associated
documentation and data
pertaining to the operation of a computer system (IEEE
Standard Glossary of Software Engineering Terminology,
What is software ?
Software is designed and built by software
engineers.
Software is used by virtually everyone in
society.
Software engineers have a moral
obligation to build reliable software that
does no harm to other people.
Software users are only concerned with
whether or not software products meet
their expectations and make their tasks
easier to complete.
What is software ?
Software is both a product and a vehicle for
delivering a product (information).
Software is engineered not manufactured.
Software does not wear out, but it does
deteriorate.
Currently, most software is still custom-built.
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W a k t u
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p e r u b a h a n
L a j u k e g a g a l a n m e n i n g k a t s e h u b u n g a n d e n g a n e f e k
Software Applications
Type
System software
Application software
Embedded software
Engineering/Scientific software
Product software
Web Applications
Artificial intelligence software
New Software Challenges
Ubiquitous computing
Creating software to allow machines of all sizes to
communicate with each other across vast networks
Netsourcing
Architecting simple and sophisticated applications
that benefit targeted end-user markets worldwide
Open Source
Distributing source code for computing applications
so customers can make local modifications easily and reliably
New economy
Building applications that facilitate mass
communication and mass product distribution using evolving concepts
Legacy Software
Many programs still provide a valuable
business benefit, even though they are one or
even two decades old.
These programs must be maintained and this
creates problems because their design is
often not amenable to change.
Legacy Software
must be adapted to meet the needs of new
computing environments or technology
must be enhanced to implement new
business requirements
must be extended to make it interoperable
with more modern systems or databases
must be re-architected to make it viable
within a network environment
Software Evolution
Process by which programs change shape,
adapt to the market place, and inherit
characteristics from preexisting programs
Unified theory for software evolution
(Lehman):
Law of continuing change
Law of increasing complexity
…
The Cost of Change
Definition Development After release 1x
1.5-6x
Important Questions for Software
Engineers
Why does it take so long to get software
finished?
Why are development costs so high?
Why can't we find all errors before we give
the software to our customers?
Why do we continue to have difficulty in
measuring progress as software is being
developed?
Software Myths
Still believed by many
managers and practitioners
Insidious because they do have
elements of truth
Every practitioner and
manager should understand
the reality of the software
business.
Software Myths:
Clients’ point of view
Myths: A general statement of
objectives is enough to get going. Fill in the details later.
Project requirements
continually change, but change can be
easily accommodated because software is flexible.
Reality:
Poor up-front
definition of the
requirements is THE
major cause of poor and late software.
Cost of the change to
software in order to fix an error increases
Software Myths:
Developers’ point of view
Myths:
Once a program is
written and works, the developer's job is done.
Until a program is
running, there is no way to assess its quality.
The only deliverable for a
successful project is a working program.
Reality:
50%-70% of the effort expended on a program occurs after it is
delivered to the customer.
Software reviews can be more effective in finding errors than testing for certain classes of errors.
A software configuration
Software Myths:
Management’s point of view
Myths: Books of standards
exist in-house so software will be developed
satisfactorily.
Computers and
software tools that are available in-house are sufficient.
We can always add
more programmers if the project gets
behind.
Reality:
Books may exist, but
they are usually not up to date and not used.
CASE(**) tools are needed
but are not usually obtained or used.
"Adding people to a late
What is Software
Engineering ?
Software engineering is the establishment
and sound engineering principles in order
to obtain economically software that is
reliable and works efficiently on real
machines (Fritz Bauer,1969)
Software engineering is [1] the application
of a systematic, disciplined, quantifiable
approach to the development, operation,
and maintenance of software, and [2] the
study of approaches as in [1] (IEEE,1993)
Why SE ?
To get the right software and to
make the software right
Complexity of software
Domain problem: Business Rule Data size: Digital and Non
Digital
Why SE ? (2)
Software must be
correct
Software correctness have to be
How should SE be
applied ?
There are 2 things to be considered in SE:
Product = Software:
Programs Documents Data
Process of how the software is build:
Product of SE
Product is obtained through stages of
development = Software Development Life
Cycle (SDLC)
Examples of life cycles (SDLC):
Waterfall model
V model
Spiral model
Fountain model
Process of SE
Management process includes:
Project management
Configuration management
Process of SE (2)
Technical process, described as methods
to be applied in a particular stage of the
s/w development life-cycle
Analysis methods
Design methods
Programming methods
Testing methods
Technical methods are leading to
When should SE be
applied ?
Pre-project
Project Initiation
Project Realisation
Who is involved ?
Manager
Project Manager
Configuration Manager
Quality Assurance Manager
Software Developer:
Analyst
Designer
Who is involved ?
Support
Administration
Technical Support for Customer
What are the costs of software
engineering?
Roughly 60% of costs are development
costs, 40% are testing costs. For custom
software, evolution costs often exceed
development costs.
Costs vary depending on the type of
system being developed and the
requirements of system attributes such as
performance and system reliability.
Distribution of costs depends on the
development model that is used.
What are software engineering
methods?
Structured approaches to software development which
include system models, notations, rules, design advice and process guidance.
Model descriptions
Descriptions of graphical models which should be produced;
Rules
Constraints applied to system models;
Recommendations
Advice on good design practice;
Process guidance
What activities to follow.
What are the attributes of good
software?
The software should deliver the required
functionality and performance to the user and should be maintainable, dependable and
acceptable.
Maintainability
Software must evolve to meet changing needs;
Dependability
Software must be trustworthy;
Efficiency
Software should not make wasteful use of system
resources;
Acceptability
Software must accepted by the users for which it was
designed. This means it must be understandable, usable and compatible with other systems.
What are the key challenges facing
software engineering?
Heterogeneity
Developing techniques for building software
that can cope with heterogeneous platforms and execution environments;
Delivery
Developing techniques that lead to faster
delivery of software;
Trust
Developing techniques that demonstrate
Professional and ethical
responsibility
Software engineering involves wider
responsibilities than simply the
application of technical skills.
Software engineers must behave in an
honest and ethically responsible way if
they are to be respected as professionals.
Ethical behaviour is more than simply
upholding the law.
Issues of professional
responsibility
Confidentiality
Engineers should normally respect the
confidentiality of their employers or clients irrespective of whether or not a formal
confidentiality agreement has been signed.
Competence
Engineers should not misrepresent their
level of competence. They should not
knowingly accept work which is outwith their competence.
Issues of professional
responsibility
Intellectual property rights
Engineers should be aware of local laws governing
the use of intellectual property such as patents,
copyright, etc. They should be careful to ensure that the intellectual property of employers and clients is protected.
Computer misuse
Software engineers should not use their technical
ACM/IEEE Code of Ethics
The professional societies in the US have
cooperated to produce a code of ethical
practice.
Members of these organisations sign up
to the code of practice when they join.
The Code contains eight Principles
related to the behaviour of and decisions
made by professional software engineers,
including practitioners, educators,
managers, supervisors and policy
makers, as well as trainees and students
of the profession.
Code of ethics - preamble
Preamble
The short version of the code summarizes aspirations at a
high level of the abstraction; the clauses that are included in the full version give examples and details of how these aspirations change the way we act as software
engineering professionals. Without the aspirations, the details can become legalistic and tedious; without the details, the aspirations can become high sounding but empty; together, the aspirations and the details form a cohesive code.
Software engineers shall commit themselves to making
the analysis, specification, design, development, testing and maintenance of software a beneficial and respected profession. In accordance with their commitment to the health, safety and welfare of the public, software
engineers shall adhere to the following Eight Principles:
Code of ethics -
principles
PUBLIC
Software engineers shall act consistently with the
public interest.
CLIENT AND EMPLOYER
Software engineers shall act in a manner that is in
the best interests of their client and employer consistent with the public interest.
PRODUCT
Software engineers shall ensure that their products
and related modifications meet the highest professional standards possible.
Code of ethics -
principles
JUDGMENT
Software engineers shall maintain integrity and
independence in their professional judgment.
MANAGEMENT
Software engineering managers and leaders shall
subscribe to and promote an ethical approach to the management of software development and
maintenance.
PROFESSION
Software engineers shall advance the integrity and
reputation of the profession consistent with the public interest.
Code of ethics -
principles
COLLEAGUES
Software engineers shall be fair to and
supportive of their colleagues.
SELF
Software engineers shall participate in lifelong
learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession.
Ethical dilemmas
Disagreement in principle with the policies of
senior management.
Your employer acts in an unethical way and
releases a safety-critical system without
finishing the testing of the system.
Participation in the development of military
weapons systems or nuclear systems.
Atribut Produk
Kinerja
Reliability
Pelayanan
Maintanability
Garansi
Mudah digunakan
Penampilan
Merek
Kemasan
Model terakhir
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Definisi
Rekayasa perangkat lunak adalah penetapan dan
penggunaan prinsip-prinsip rekayasa yang tangguh/ teruji dalam upaya memperoleh perangkat lunak secara ekonomis, handal dan bekerja efisien di mesin nyata, dan berkaitan dengan metode dan kaidah yang diperlukan dalam mengembangkan perangkat lunak untuk computer.
Sedangkan pengertian rekayasa perangkat lunak
menurut IEEE :Rekayasa perangkat lunak adalah
pendekatan sistematis untuk pengembangan, operasi, pemeliharaan dan pemberhentian pemakaian perangkat lunak.
43 Rekayasa Perangkat Lunak - Citra N., S.Si,
Prinsip Perangkat Lunak
Kekakuan (Rigor),
Rekayasa yang dilakukan harus sesuai dengan keinginan user, walupun terkadang diperlukan kreativitas perekayasa untuk membuat perangkat lunak.
Resmi (formal)
Pemilihan salah satu metodologi/pendekatan
perangkat lunak, berdampak pada harus
dilaksanakannya aktivitas rekayasa sesuai
dengan metodologi yang dipilih, serta notasi yang dipilih harus selalu konsisten digunakan
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Prinsip Perangkat Lunak
Pemisahan kepentingan
Berkaitan dengan apek-aspek persoalan : melebarnya focus kerja, kompleksitas sistem.
Abstraksi
Menggambarkan keseluruhan sistem dalam bentuk yang sederhana
Modularitas
Mendekomposisikan persoalan menjadi modul-modul independent sehingga memisahkan perhatian mengenai persoalan internal modul dan interaksi modul-modul dengan lingkungan luarnya.
45 Rekayasa Perangkat Lunak - Citra N., S.Si,
Karakteristik Perangkat
Lunak
Perangkat lunak dibangun dan dikembangkan,
tidak dibuat dalam bentuk yang klasik.
Walaupun perkembangan antara perangkat
keras dan perangkat lunak sangat ekuivalen,
namun aktivitas diantara keduanya sangat
berbeda.
Perangkat lunak tidak pernah usang,
Sebagian besar perangkat lunak dibuat secara
custom built, serta tidak dapat dirakit dari
komponen yang sudah ada
46 Rekayasa Perangkat Lunak - Citra N., S.Si,
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W a k t u
T in gk at K eg ag al an
K e m a t i a n
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W a k t u
T in gk at K eg ag al an
K u r v a i d e a l K u r v a a k t u a l
p e r u b a h a n
L a j u k e g a g a l a n m e n i n g k a t s e h u b u n g a n d e n g a n e f e k
Tahapan Umur Perangkat
Lunak
Periode Simbolisasi Penyebab Solusi
Pembuatan DFR (Decreasing Failure Rate) Defect, rendahnya control kualitas, Quality control, Pengujian penerimaan, Pemakaian CFR (Constant Failure Rate)
Human error Redudancy, User friendly, Kadaluarsa IFR (Increasing Failure Rate) Peningkatan kebutuhan,
prosedur kerja baru,
Teknologi, Modifikasi
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Pemodelan Sistem
Asumsi, digunakan untuk mengurangi jumlah kemungkinan (permutasi) dan variasi yang mungkin. Penyederhanaan, digunakan untuk menciptakan
model dengan waktu yang tepat.
Pembatasan (Boundaries), digunakan untuk membatasi lingkup sistem.
Batasan (Constraint), digunakan untuk menunjukkan cara dimana model tersebut diciptakan dan pendekatan yang dilakukan pada saat model diimplementasikan.
Preferensi, digunakan untuk menunjukkan arsitektur yang dipilih untuk semua data, fungsi dan teknologi.
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Maintainability
(dapat dipelihara)
Software bisa menangani perubahan spek
kebutuhan
Dependability
(dapat diandalkan)
Aman, selamat, tidak menyebabkan
keruksakan fisik
Efficiency
(Efisien)
Software mampu mengoptimalkan resource
Acceptability
(Kemampupakaian)
Software bisa diterima user sebagaimana
rancangan. Mudah dimengerti, digunakan and compatible dengan sistem yang lain
Ciri-ciri software yang baik
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