Systems design

Systems design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements. Systems design could be seen as the application of systems theory to product development. There is some overlap with the disciplines of systems analysis, systems architecture and systems engineering.^[1][2]

Overview

If the broader topic of product development "blends the perspective of marketing, design, and manufacturing into a single approach to product development,"^[3] then design is the act of taking the marketing information and creating the design of the product to be manufactured. Systems design is therefore the process of defining and developing systems to satisfy specified requirements of the user.

Until the 1990s, systems design had a crucial and respected role in the data processing industry. In the 1990s, standardization of hardware and software resulted in the ability to build modular systems. The increasing importance of software running on generic platforms has enhanced the discipline of software engineering.

Object-oriented analysis and design methods are becoming the most widely used methods for computer systems design. The UML has become the standard language in object-oriented analysis and design. It is widely used for modeling software systems and is increasingly used for high designing non-software systems and organizations.

Architectural design

The architectural design of a system emphasizes the design of the systems architecture that describes the structure, behavior and more views of that system and analysis.

Logical design

The logical design of a system pertains to an abstract representation of the data flows, inputs and outputs of the system. This is often conducted via modelling, using an over-abstract (and sometimes graphical) model of the actual system. In the context of systems, designs are included. Logical design includes entity-relationship diagrams (ER diagrams).

Physical design

The physical design relates to the actual input and output processes of the system. This is explained in terms of how data is input into a system, how it is verified/authenticated, how it is processed, and how it is displayed. In physical design, the following requirements about the system are decided.

1. Input requirement,
2. Output requirements,
3. Storage requirements,
4. Processing requirements,
5. System control and backup or recovery.

Put another way, the physical portion of systems design can generally be broken down into three sub-tasks:

1. User Interface Design
2. Data Design
3. Process Design

User Interface Design is concerned with how users add information to the system and with how the system presents information back to them. Data Design is concerned with how the data is represented and stored within the system. Finally, Process Design is concerned with how data moves through the system, and with how and where it is validated, secured and/or transformed as it flows into, through and out of the system. At the end of the systems design phase, documentation describing the three sub-tasks is produced and made available for use in the next phase.

Physical design, in this context, does not refer to the tangible physical design of an information system. To use an analogy, a personal computer's physical design involves input via a keyboard, processing within the CPU, and output via a monitor, printer, etc. It would not concern the actual layout of the tangible hardware, which for a PC would be a monitor, CPU, motherboard, hard drive, modems, video/graphics cards, USB slots, etc. It involves a detailed design of a user and a product database structure processor and a control processor. The H/S personal specification is developed for the proposed system.

Project

Cost Metrices:

For unadjusted function points:

Function type Low Average High total

External input 0*3 3*4 0*6 12

External output 0*4 3*5 0*7 15

External Inquiries 0*3 0*4 0*6 0

Internal logical files 0*5 1*7 0*10 7

External logical files 0*7 0*10 0*15 0

For adjusted function points:

No. GCS’s Degree of influence

1 Data communications 4

2 Distributed data processing 4

3 Performance 5

4 Heavily used configuration 3

5 Transaction rate 5

6 data entry 4

7 End-user efficiency 4

8 Update 4

9 Complex processing 3

10 Reusability 3

11 Installation ease 2

12 Operational ease 5

13 Multiple user 4

14 Facilitate change 3

Total value adjusted factor 53

I.D Task Name Duration Predecessors

1. Initiation -

2. Assign key persons 12 -

3. Prepare project plan 18 3

4. Prepare CM plan 11 4

5. Prepare QA plan 10 4

6. Requirements 2

7. 19 4

8. Analysis Requirements 16 8

9. Development SRS 18 9

10. Prepare development plan 19 10, 4

11. Design 7

12. Preliminary design 14 10

13. Final design 20 13

14. Design Review 9 14

15. Design approval 7 15

16. Construction 12

17. Collect material 10 16

18. Coding 40 16, 14

19. Unit testing 14 19

20. Peer review 23 20

21. Testing 17

22. Create test scenarios 15 10

23. Approve test cases 10 23

24. Integration 17 24

25. System

Project

Cost Metrices:

For unadjusted function points:

Function type	Low	Average	High	total
External input	0*3	3*4	0*6	12
External output	0*4	3*5	0*7	15
External Inquiries	0*3	0*4	0*6	0
Internal logical files	0*5	1*7	0*10	7
External logical files	0*7	0*10	0*15	0

For adjusted function points

No.	GCS’s	Degree of influence
1	Data communications	4
2	Distributed data processing	4
3	Performance	5
4	Heavily used configuration	3
5	Transaction rate	5
6	data entry	4
7	End-user efficiency	4
8	Update	4
9	Complex processing	3
10	Reusability	3
11	Installation ease	2
12	Operational ease	5
13	Multiple user	4
14	Facilitate change	3
Total value adjusted factor		53

I.D Task Name Duration Predecessors

1. Initiation -

2. Assign key persons 12 -

3. Prepare project plan 18 3

4. Prepare CM plan 11 4

5. Prepare QA plan 10 4

6. Requirements 2

7. 19 4

8. Analysis Requirements 16 8

9. Development SRS 18 9

10. Prepare development plan 19 10, 4

11. Design 7

12. Preliminary design 14 10

13. Final design 20 13

14. Design Review 9 14

15. Design approval 7 15

16. Construction 12

17. Collect material 10 16

18. Coding 40 16, 14

19. Unit testing 14 19

20. Peer review 23 20

21. Testing 17

22. Create test scenarios 15 10

23. Approve test cases 10 23

24. Integration 17 24

25. System testing 20 25

Activity cost :

I.D Task Name Cost

1. Initiation 36 $

2. Assign key persons 8 $

3. Prepare project plan 9 $

4. Prepare CM plan 10 $

5. Prepare QA plan 9 $

6. Requirements 20 $

7. Gather requirement 20 $

8. Analysis Requirements 35 $

9. Development SRS 8 $

10. Prepare development plan 3 $

11. Design 18 $

12. Preliminary design 7 $

13. Final design 5 $

14. Design Review 4 $

15. Design approval 5 $

16. Construction 52 $

17. Collect material 7 $

18. Coding 25 $

19. Unit testing 15 $

20. Peer review 4 $

21. Testing 28 $

22. Create test scenarios 5 $

23. Approve test cases 3 $

24. Integration 13 $

25. System testing 8 $

Related disciplines

• Benchmarking – is an effort to evaluate how current systems perform
• Computer programming and debugging in the software world, or detailed design in the consumer, enterprise or commercial world - specifies the final system components.
• Design – designers will produce one or more 'models' of what they see a system eventually looking like, with ideas from the analysis section either used or discarded. A document will be produced with a description of the system, but nothing is specific – they might say 'touchscreen' or 'GUI operating system', but not mention any specific brands;
• Requirements analysis – analyzes the needs of the end users or customers
• Systems architecture – creates a blueprint for the design with the necessary structure and behavior specifications for the hardware, software, people and data resources. In many cases, multiple architectures are evaluated before one is selected.
• System testing – evaluates the system's actual functionality in relation to expected or intended functionality, including all integration aspects.

Alternative design methodologies

Rapid application development (RAD)

Rapid application development (RAD) is a methodology in which a systems designer produces prototypes for an end-user. The end-user reviews the prototype, and offers feedback on its suitability. This process is repeated until the end-user is satisfied with the final system.

Joint application design (JAD)

Joint application design (JAD) is a methodology which evolved from RAD, in which a systems designer consults with a group consisting of the following parties:

• Executive sponsor
• Systems Designer
• Managers of the system

JAD involves a number of stages, in which the group collectively develops an agreed pattern for the design and implementation of the system.

See also

References

1. ↑  This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".
2. ↑  This article incorporates public domain material from the United States Department of Defense document "Dictionary of Military and Associated Terms".
3. ↑ Ulrich & Eppinger (2000). Product Design & Development. Irwin McGraw-Hill. ISBN 0-07-229647-X. 

Further reading

• Bentley, Lonnie D., Kevin C. Dittman, and Jeffrey L. Whitten. Systems analysis and design methods. (1986, 1997, 2004).
• C. West Churchman (1971). The Design of Inquiring Systems: Basic Concepts of Systems and Organization. New York: Basic Books. ISBN 0-465-01608-1. 
• William Gosling (1962). The design of engineering systems. New York: Wiley. 
• Hawryszkiewycz, Igor T. Introduction to systems analysis and design. Prentice Hall PTR, 1994.
• Levin, Mark Sh. Modular systems design and evaluation. Springer, 2015.
• Maier, Mark W., and Rechtin, Eberhardt (2000). The Art of Systems Architecting (Second ed.). Boca Raton: CRC Press.  CS1 maint: Uses authors parameter (link)
• Saltzer, J.H.; et al. (November 1984). "End-to-End arguments in Systems Design". ACM Transactions in Computer Systems. 2 (4): 277–288. 
• Ulrich, Karl T.; Eppinger, Steven D. (2000). Product Design and Development (Second ed.). Boston: Irwin McGraw-Hill. 
• Whitten, Jeffrey L.; Bentley, Lonnie D.; Dittman, Kevin C. (2004). Fundamentals of systems analysis and design methods. 

External links

Look up systems design in Wiktionary, the free dictionary.

• Interactive Systems Design. Course by Chris Johnson, 1993