- The legacy problem - too many devices use the existing standard, even when it may be poorly designed. Standardization is almost impossible due to the wide use of the legacy, which makes changes expensive.
- Lack of attention to customer needs on even simple things is often symptomatic of larger issues that have greater impact.
Constraints §
- The thoughtful use of constraints in design lets people readily determine the proper course of action, even in a novel situation.
Kinds of Constraints §
- Physical Constraints
- Physical limitations constrain possible operations. They rely upon properties of the physical world or their operation.
- They are more effective if they are easy to see and interpret.
- Forcing functions are a physical constraint—situations in which the actions are constrained so that failure at one stage prevents the next step from happening.
- Forcing functions are the extreme case of strong constraints that can prevent inappropriate behavior
- Interlocks forces operations to take place in proper sequence. In most cases it is to prevent something dangerous (an example is a dead man’s switch).
- Lock-Ins keep an operation active, preventing someone from prematurely stopping it (i.e., alerts that prevent exiting an unsaved document).
- Lockouts prevents someone from entering a dangerous space or occurring. It prevents an action until the desired operations have been done.
- Forcing functions can be a nuisance in normal storage, leading to people deliberately disabling them.
- A clever designer minimizes the nuisance value of the forcing function without sacrificing safety.
- Cultural Constraints
- Each culture has a set of allowable actions for social situations.
- Cultural issues are at the root of many of the problems we have with new machines: there are as yet no universally accepted conventions or customs for dealing with them.
- Cultural constraints are likely to change with time.
- Conventions are a cultural constraint associated with how people behave. They provide those knowledgeable of the culture with powerful constraints on behavior.
- Conventions can be codified into standards (formal or informally agreed upon), laws or both.
- Signals are useful for communicating between people, but only if both people follow the same conventions.
- People who violate conventions are marked outsiders.
- Unknown norms lead to discomfort and confusion.
- Semantic Constraints
- Constraints that rely upon the meaning of the situation to control the set of possible actions.
- They rely upon our knowledge of the situation and the world.
- Semantic constraints can change with time. Meanings of today may not be the meanings of the future.
- Logical Constraints
- Constraints that rely on logic (i.e., there is only one place where X could go).
- Natural mappings can help establish logical constraints (i.e., between spatial layout of the controls and the devices).
Discoverability and Conventions §
- Visible affordances and signifiers (see here) can act as physical constraints.
- In many cases, an understanding of potential actions derived from perceived affordances come from conventions. The interpretation of a perceived affordance is a cultural convention.
- On the whole, consistency is to be followed Consistency allows us to transfer from one system to another.
- People invariably object and complain whenever a new approach is introduced into an existing array of products and systems
- If a new way of doing things is only slightly better than the old, it is better to be consistent.
- If there is a change, everybody has to change
- When a new way of doing things is vastly superior to another, then the merits of change outweigh the difficulty of change.
- Natural mappings derive from cultural conventions or constraints.
- The principle of desperation: If all else fails, standardize
- When no other solution appears possible, simply design everything the same way.
- This introduces a new cultural constraint that makes it easier to remember what to do even if knowledge is in the world.
- Ideally, standards should reflect conceptual models not physical mechanics.
- When visual signifiers and feedback are not enough, use sound to convey information about its source.
- Sounds can be annoying. Hence they should convey an action that is immediately taking place but is otherwise not visible.
- One of the virtues of sounds is that they can be detected even when attention is applied elsewhere. But this virtue is also a deficit, for sounds are often intrusive and difficult to keep private.
- The absence of sound can mean an absence of knowledge, and if feedback from an action is expected to come from sound, silence can lead to problems
- Skeumorphism - the technical term for incorporating old, familiar ideas into new technologies, even though they no longer play a functional role. This eases the transition from old to new.
Links §