1. Software Design Lecture : 5

3. Introduction to Software Design
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4. Software Design in a Nutshell
Structures are the most stable things in your system
They have to hold even after years.
System design
Lays down a structure for the system
Divides the future system in parts which can be
managed
If you do it right, you are awarded with further
abstraction
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5. Importance of Software Design
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6. Software Design Activities
“The process of defining the architecture, components, interfaces, and other characteristics of a system or
component.” ,

7. Architectural design IEEE Standard
“The process of defining a collection of hardware and software components and their interfaces to establish the framework for the development of a computer system”
IEEE Standard

8. Preliminary design
“The process of analyzing design alternatives and defining the architecture, components, interfaces, and timing and sizing estimates for a system or component.” ,

9. Detailed design
“ The process of refining and expanding the preliminary design of a system or component to the extent that the design is sufficiently complete to be implemented”

10. Overall Design Activities
High level Design / Architectural Design
Hierarchical decomposition of the system into
subsystems
Determine components and assign to subsystems
Determine relationships between components
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11. Software Architecture
“The software architecture of a program or computing system is the structure or structures of the system, which comprise software elements, the externally visible properties of those elements, and the relationships among them “
From :Bass, L., Clements, P., Kazmann, R. (2003): Software
Architecture in Practice, 2nd Edition, Addison-Wesley ,

12. Lehman‘s First Law of Software Evolution
“A program that is used as an implementation of software specification reflects some reality, undergoes continual change or becomes progressively less useful.”
Result:
The System will change (or it will vanish) ,

13. Bersoff‘s First Law of System Engineering
“No matter where you are in the system life cycle, the system will change and the desire to change it will persist throughout the life cycle.”
Result:
The System will change even at development stage

14. Cost of Bad Design
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15. Design Metaphor
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