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Components Based Design and Development
Computer Engineering Studies
Universidad Carlos III de Madrid
1Juan Llorens– Software Engineering Overview
Juan Llorens
Högskolan på Åland – Finland / Universidad Carlos III de Madrid - Spain
Juan.llorens@uc3m.es
Unit 2: Software Engineering Quick Overview
Software Engineering
• Engineering...“the profession in which
a knowledge of the mathematical and natural sciences gained by study, experience and practiceis applied with judgment
to develop ways to utilize, economically, the materials and forces of nature for the benefit of mankind.” (Accreditation Board for Engineering
2Juan Llorens– Software Engineering Overview
nature for the benefit of mankind.” (Accreditation Board for Engineering and Technology, 1996).
• Particularities of software engineering– The “product” (software)
– A lot of development, little engineering discipline
– Frequent changes in the product
– It is not seen as necessary by the “so called” software engineers
From Gonzalo Genova
Software Engineering
• The economies of ALL developed nations are dependent on software.
• More and more systems are software controlled
• Software engineering is concerned with theories, methods and tools for
3Juan Llorens– Software Engineering Overview
• Software engineering is concerned with theories, methods and tools for professional software development.
• Expenditure on software represents a significant fraction of GNP in all developed countries.
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
The systems engineering process
System
design
Requirements
definition
System
evolution
System
decommissioning
4Juan Llorens– Software Engineering Overview
System
integration
Sub-system
development
design
System
installation
evolution
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 2
Inter-disciplinary involvement
Electronic
engineering
Mechanical
engineering
Software
engineering
5Juan Llorens– Software Engineering Overview
ATC systems
engineering
Electrical
engineering
User interface
design
Architecture
Structural
engineering
Civil
engineering
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 2
What is a software process?
Objectives, needs, ideas
6Juan Llorens– Software Engineering Overview
problems, failures,..
“Software application”
BNot a Software system
How is a software project done?
What is a software process?
• A set of activities whose goal is the development or evolution of software.
• Generic activities in all software processes are:– Specification - what the system should do and its development constraints– Development - production of the software system
7Juan Llorens– Software Engineering Overview
– Validation - checking that the software is what the customer wants– Evolution - changing the software in response to changing demands.
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
What is a software process model?
• A simplified representation of a software process, presented from a specific perspective.
• Examples of process perspectives are– Workflow perspective - sequence of activities;
– Data-flow perspective - information flow;
8Juan Llorens– Software Engineering Overview
– Data-flow perspective - information flow;
– Role/action perspective - who does what.
• Generic process models– Waterfall;
– Iterative development;
– Component-based software engineering.
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
Usual workflow Activities
design implementation testsReq. analysis
9Juan Llorens– Software Engineering Overview
Not so Usual workflow Activities
Project Mgmt Estimation DebriefingVocabulary Id.
Risk Mgmt. Project Plan. IndexingSw For Reuse
Types of Software Processes : the waterfall process
analysis of requirements
Need
A single iteration
10Juan Llorens– Software Engineering Overview
design
implementation
tests Final product
is an idealization never realized in this pure form
Iterative process [spiral]
Requirements analysis design
N iterations
11Juan Llorens– Software Engineering Overview
implementationtests
need
N versions of the product, documentation...
final product
Iterative and incremental process
• Enables the evolution in parallel of several workflows, and by that the work in parallel of several teams of people
• the different versions of the documents produced in each iteration are not necessarily compatible between them: organize well the documentation
iteration 1 iteration 2 iteration 3
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analysis
(version 1)
analysis
(version 2)
analysis
(version 3)
design
(version 1)
design
(version 2)
implementation
(version 1)
UP: Phases, iterations and workflows
requirements
analysis
Phases of the life cycle
Workflows Inception Elaboration Construction Transition
an iteration in the
phase of Elaboration
13Juan Llorens– Software Engineering Overview
design
implementation
tests
iterations
Preliminary
iteration(s)
Iter.
#1Iter.
#2
Iter.
#n
Iter.
#n+1
Iter.
#n+2
Iter.
#m
Iter.
#m+1
My Favorite workflow structure for Development
Softw
are
for R
euse
New Project
PMgnt
Risk
Plan-Est
Req Ana
Softw
are
with
Reuse
Req Cap
Voc
Sw for reuse
Find + Reuse
14Juan Llorens– Software Engineering Overview
Softw
are
for R
euse
New Solution
Req Ana
Arc. Des
D Des
Dev
Tes
Db
Ix
Softw
are
with
Reuse
CM
WG Traceability
DocumentMngmnt.
My Favorite dataflow structure for Development
PMgnt
Risk
Plan-Est
Req Ana
Req Cap
Voc Ontology
Document Templates
Gantt Diagrams
Spreadsheets
Text based Requirements
Text Based Risks
Requirements Models
15Juan Llorens– Software Engineering Overview
Req Ana
Arc. Des
D Des
Dev
Tes
Db
Ix
Requirements Models
Documents
Architectural Models
Software Models
Code
Reports
AcknowledgedReports
Documents
Documents
Documents
Documents
Terminology of UP Classical terminology
requirementsrequirements analysis
analysis
Other frameworks and nomenclatures
16Juan Llorens– Software Engineering Overview
design design
implementationimplementation
integration
tests tests
Eric Braude, Software Engineering. An Object-Oriented Perspective, John Wiley & Sons, 2001, p. 30.
• divide a project in mini-projects, easier to manage and complete
• each mini-project is an iteration
• each iteration contains all the elements of a normal project:– planning
– analysis and design
– construction
How to perform an Iterative Software Process
17Juan Llorens– Software Engineering Overview
– construction
– integration and tests
– generate a version of the product (internal or external)
• each iteration generates a baseline that includes a partially completed version of the final system, and all the associated documentation
• the successive iterations build on top of each other until the final system is finished
• the difference between two baselines is known as an increment
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
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• Rules– Constraints applied to system models;
• Recommendations– Advice on good design practice;
• Process guidance– What activities to follow.
Based on Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
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.
19Juan Llorens– Software Engineering Overview
requirements of system attributes such as performance and system reliability.
• Distribution of costs depends on the development model that is used.
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
Software costs
• Software costs often dominate computer system costs. The costs of software on a PC are often greater than the hardware cost.
• Software costs more to maintain than it does to develop. For systems with a long life, maintenance costs may be several times development costs.
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• Software engineering is concerned with cost-effective software development.
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
Activity cost distributionWaterfall model
Iterative development
Specification Design Development Integration and testing
25 50 75 1000
25 50 75 1000
21Juan Llorens– Software Engineering Overview
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
Component-based software engineering
Development and evolution costs for long-lifetime systems
System evolution
10 200 30 4000
System development
Specification Development Integration and testing
25 50 75 1000
Specification Iterative development System testing
Product development costs
22Juan Llorens– Software Engineering Overview
©Ian Sommerville 2004 - Software Engineering, 7th edition. Chapter 1
The maturity of the Software Engineering discipline (swing)
1. Real need: what the customer really wanted.
2. Client side: what the client was able to describe as his/her clear need.
3. Sale process: what the software manufacturer promised the client.
4. Requirements: the final understanding of what the customer described as requirements.
23Juan Llorens– Software Engineering Overview
the customer described as requirements.
5. Analysis: how was planned that the system should finally work at the client side.
6. Design: how the system should perform the analysed functionality.
7. Coding: what the programmer finally produced.
8. On-site installation: what was really installed in the client site.
9. Test: what the responsibles saw in the system.
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