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Conceptual design

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Architecture: associates system components with capabilities ... DO WHILE I is between 1 and (length of L)-1: ... Critical design review. presents technical ... – PowerPoint PPT presentation

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Title: Conceptual design


1
Conceptual design
2
Tells the customer what the system will do
3
  • Answers the following
  • Where will the data come from?

4
  • What will happen to the data in the system?

5
  • What will be the system look like to users?

6
  • What choices will be offered to users?

7
  • What is the timing of events?

8
  • What will the reports and screens look like?

9
  • Characteristics of good conceptual design
  • in customer language with no technical jargon

10
  • describes system functions

11
  • independent of implementation

12
  • linked to requirements

13
Technical design
  • Tells the programmers what the system will do
  • Includes
  • major hardware components and their function
  • hierarchy and function of software components
  • data structures
  • data flow

14
  • independent of implementation

15
Five ways to create designs
  • Modular decomposition
  • Data-oriented decomposition
  • Event-oriented decomposition
  • Outside-in design
  • Object-oriented design

16
Three design levels
  • Architecture associates system components with
    capabilities
  • Code design specifies algorithms and data
    structures for each component
  • Executable design lowest level of design,
    including memory allocation, data formats, bit
    patterns

17
Design styles
  • Pipes and filters
  • Object-oriented design
  • Implicit invocation
  • Layering
  • Repositories
  • Interpreters
  • Process control
  • Client-server

18
Example of implicit invocation
19
Example of abstraction
Rearrange L in non-decreasing order
DO WHILE I is between 1 and (length of L)-1
Set LOW to index of smallest value in L(I),
..., L(length of L)
Interchange L(I) and L(LOW) END DO
20
Important design issues
  • Modularity and levels of abstraction
  • Collaborative design
  • Designing the user interface
  • metaphors, mental model, navigation rules, look
    and feel
  • cultural issues
  • user preferences
  • Concurrency
  • Design patterns and reuse

21
Characteristics of good design
  • Component independence
  • coupling
  • cohesion
  • Exception identification and handling
  • Fault prevention and tolerance
  • active
  • passive

22
Techniques for improving design
  • Reducing complexity
  • Design by contract
  • Prototyping design
  • Fault-tree analysis

23
Design evaluation and validation
  • Mathematical validation
  • Measuring design quality
  • Comparing designs
  • one specification, many designs
  • comparison table
  • Design reviews

24
(No Transcript)
25
Design reviews
  • Preliminary design review
  • examines conceptual design with customer and
    users
  • Critical design review
  • presents technical design to developers
  • Program design review
  • programmers get feedback on their designs before
    implementation

26
QUESTION FOR DESIGN REVIEW
27
Is it a solution to the problem?
28
Is it modular, well-structured, and easy to
understand?
29
Can we improve the structure and
understandability?
30
Is it portable to other platforms?
31
Is it reusable?
32
Is it easy to modify or expand?
33
Does it support ease of testing?
34
Are the algorithms appropriate, or can they be
improved?
35
Does it use appropriate techniques for handling
faults and preventing failures?
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