Week 8 lecture summary of Design Decision consists of..
1. Factor of Safety
2. Redundancy
3. Flexibility-Usability Trade-Off
4. Satisficing
5. Ockham’s Razor
6. Form Follows Function
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According to the Universal Principles of Design by Lidwell W., Holden, K., & Butler, J., (2003)
I. Factor of Safety
The use of more elements than is thought to be necessary to offset the effects of unknown variables and prevent system failure
-: Designers in designing deals with unknown even though how knowledgeable the designers, the designers will face the inevitable in the process of designing. Factors of safety are used to offset the potential effects of these unknowns. This is achieved by adding materials and components to the system in order to make the design exceed the specification that is believed to be necessary to meet the design requirements. Materials and components will be added to the design in order to make the design exceed the specification that is believed to be necessary to meet the design requirements. Increasing the safety factor in a design e.g. adding material also add more cost to the design. Safety factor can be reduced but with caution.

Figure 8.1 A motorcycle handbrake and foot brake can serves as Factor of Safety. In case foot brake is malfunction, the handbrake still able to do the job of stopping the motorcycle. (Photo source: Own motorcycle)
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II. Redundancy
The use of more elements than necessary to maintain the performance of a system in the event of failure of one or more of the elements.
-: System failure is the failure of a system to achieve a goal. It is inevitable that elements within a system will fail. Redundancy is the surest method of preventing system failure. There are four kinds of redundancy: Diverse, Homogenous, Active, and Passive.
-: the use of multiple elements of different types. It's resistant to a single cause of failure, but is complex to implement and maintain.
Figure 8.3 A Pattern-Lock in Samsung smartphone. If the user draw the pattern incorrectly for 5 times the phone will block, the the user need unlock it using the back up pin or using the email account associated with the phone. (Photo source: Own handphone)
2. Homogenous
-: the use of multiple elements of a single type. It's relatively simple to implement and maintain but is susceptible to single causes of failure.
Figure 8.4 A spectacle (Photo source: Own spectacle)
3. Active
-: the application of redundant elements at all times. It's guards against both system and element failure. Allows for element failure, repair, and substitution with minimal disruption of system performance.
Figure 8.5 Multiple independent pillar at FSGK.
4. Passive
-: the application of redundant elements only when an active element fails. Passive redundancy is ideal for noncritical elements, but it will result in system failure when used for elements critical to system operation. Passive redundancy is the simplest and most common kind of redundancy.
Figure 8.6 A Samsung smartphone in low battery and in charging mode.
___________________________________________________________________________________ III. Flexibility-Usability Trade-Off
As the flexibility of a system increases, the usability of the system decreases.
-: Flexible designs can perform more functions than specialized designs, but they perform the functions less efficiently. It's more complex than inflexible design and more complex to use. Flexibility has real costs in terms of complexity, usability, time and money. The flexibility-usability tradeoff has implications for weighing the relative importance of flexibility versus usability in a design.
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IV. Satisficing
It is often preferable to settle for a satisfactory solution, rather than pursue an optimal solution.
-: The best design decision is not always the optimal design decision. In certain circumstances, the success of a design is better served by design decisions that roughly satisfy (i.e., satisfice), rather than optimally satisfy, design requirements. There are three kinds of problems for which satisficing should be considered:
1. Very complex problems.
-: Complex design problems are characterized by a large number of interacting variables and a large number of unknowns.
2. Time-limited problems.
-: Time-limited problems are characterized by time frames that do not permit adequate analysis or development of an optimal solution.
3. Problems for which anything beyond a satisfactory solution yields diminishing returns.
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Figure 8.7 |
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Figure 8.8 |
Example: Powerbank Pineng, even the design is quite big, but it give a satisfaction to us as a user because it help to recharge our smartphones and can charging for two smartphones at the same time. (Photo source: Own powerbank)
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V. Ockham’s Razor
Given a choice between functionally equivalent designs, the simplest design should be selected.
-: Ockham’s razor asserts that simplicity is preferred to complexity in design. Many variations of the principle exist, each adapted to address the particulars of a field or domain of knowledge. A few examples include:
• “Entities should not be multiplied without necessity.” William of Ockham
• “That is better and more valuable which requires fewer, other circumstances being equal.” Robert Grosseteste
• “Nature operates in the shortest way possible.” Aristotle
• “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.” Isaac Newton
• “Everything should be made as simple as possible, but not simpler.” Albert Einstein
Implicit in Ockham’s razor is the idea that unnecessary elements decrease a design’s efficiency, and increase the probability of unanticipated consequences. Unnecessary weight, whether physical, visual, or cognitive, degrades performance. Unnecessary design elements have the potential to fail or create problems.
Figure 8.9 An ordinary mouse and an ergonomic mouse.
(Photo source own mouse and friend mouse)
________________________________________________________________________________VI. Form Follows Function
Beauty in design results from purity of function.
-: The form follows function corollary is interpreted in one of two ways—as a description of beauty or a prescription for beauty. The descriptive interpretation is that beauty results from purity of function and the absence of ornamentation. The prescriptive interpretation is that aesthetic considerations in design should be secondary to functional considerations.
The descriptive interpretation—i.e., that beauty results from purity of function— was originally based on the belief that form follows function in nature.
The prescriptive interpretation—i.e., that aesthetic considerations in design should be secondary to functional considerations—was likely derived from the descriptive interpretation.
Figure 8.1.0 A dirt bike helmet and ordinary motorcycle helmet.
(Photo source: Friends helmet)
(Photo source: Friends helmet)