Error prevention :. Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.
Recognition rather than recall :. Minimize the user's memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate. Flexibility and efficiency of use :. Accelerators—unseen by the novice user—may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users.
Allow users to tailor frequent actions. Aesthetic and minimalist design :. Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility. Help users recognize, diagnose, and recover from errors :. Error messages should be expressed in plain language no codes , precisely indicate the problem, and constructively suggest a solution.
Help and documentation :. Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation.
Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large. Although Nielsen is considered the expert and field leader in heuristics, Jill Gerhardt-Powals also. Developed by Therithal info, Chennai. Toggle navigation BrainKart. Home Software Engineering Design Heuristic. Posted On : Design Heuristic The main goal of heuristic evaluations is to identify any problems associated with the design of user interfaces. This looks like ancient calculator: when 0, 1, 2 and then 'many'.
Consequence: people are quite susceptible to small numbers. Say something like "this consists of 3 steps" and people will get it. Don't say "seven". See also Humans are not designed for Big Numbers. Don't start to abstract or DRY from just two things.
Wait until you have at least 3 of them. See also Duplication is better than poor abstraction. If your reasoning is complicated by cognitive overload that you have after a problem you are trying to solve and there is no obvious way to make a first step towards solution, take a step back and start working with Periphery.
Good example is legacy code: poor periphery like bad variable names, wrong responsibilities in classes, even those who are distant to your problem, bad folder structure, etc might look completely irrelevant to the core of your problem but still it contributes to the cognitive overload - try to clean up periphery and you will see that the core of your problem is now more clear and approachable than it was before.
Another word for Periphery is Background, see also Deconcentation of Attention. If a feature is hard to implement it might indicate that it is something wrong with the feature or product. If you know True Name of something you have power over it. See also Mass and Gravity. A class violates Single Responsibility Principle if it contains implementation of more than one design pattern. Of course there are exceptions.
Archetype is an umbrella concept for other concepts like: prototype , proof of concept , minimal viable product. Archetype means something simple and coherent. If you know the archetype of something you understand the essense of it.
A complex system can be traced back to a one or a number of underlying archetypes. Interesting side note: as far as I see it, the tendency is that engineers as they grow their software bigger, do not care much about the underlying archetypes.
Imagine how easy it would be to learn about the software if it would contain itself in its earliest forms of being source code, documentation, drafts etc. Great example: Rust programming language had to start from somewhere. An excellent method for determining the meaning of something is to find out how it comes to be what it is. Strong, "tight", encapsulation is good but don't forget about the users: Operations people.
Good example is debugging facilities - if you close everything then you leave the ops people, who might be you, without any tools to understand or tweak your system. Flexibility breeds bugs. Another strategy you can use to prevent bugs is to strip unnecessary flexibility from your designs The trouble with flexible designs is that the more flexible they are, the harder it is to detect bugs. Flexible features are troublesome because they can lead to unexpected "legal" situations that you didn't think to test for even realize were legal When you implement features in your own projects, make them easy to use; don't make them unnecessary flexible.
There is a difference. Don't allow unnecessary flexibility. Over the years I have seen at least three big units of a hardly manageable legacy code where each of them was built on two almost identical entities.
There are two ways of such things to co-exist:. It seems that historically in all three cases it started with one entity that accumulated its features along the way, then came the other which was so similar to the first that programmer avoided extraction of similar modules that both entities had and went with subclassing to get the result quickly or with 2 parallel hierarchies.
To these days I still didn't see or create an elegant solution to this problem. See also "Hard Feature". One of the key concerns is Control: where control should or should not be, what should have control be active and what should not have passive. Software should be designed in such a way that there always should be a dedicated place where it is obvious how the control and work flow through the software.
This should be effective on all levels of abstraction and for each level of abstraction, such dedicated software should be free of the lower-level implementation details that discourage easy understanding of context. If something creates a low-level implementation noise on a given level, it might be a good sign that one or more underlying lower layers exist where that lower-level implementation can be represented as a high-level workflow logic sequence of steps or algorithm. The lower-level modules should not have control over higher-level modules.
Two shortcuts: humans should dominate machines , business logic should dominate the system's implementation details. Overlapping things is a challenge for a human mind and therefore is bad for the whole software lifecycle: design, development, testing and maintenance. This might be two or more classes that do the same thing.
This might be two or more people whose responsibilities overlap. Nancy Leveson says Overlapping Control is one of the greatest sources of safety problems: two controllers whose areas of responsibilities overlap see "Engineering a Safer World". The top-level controllers should always have a control over the bottom-level elements. If the controllers include both humans and automation, the humans should always be able to intervene and take over the control provided by the automation.
Missing, insufficient or incorrect feedback is a great source of troubles for any system. Example 2: the inner block has a multiline routine which could actually be another function that works on one. At the same time this inner block on many. Unless we create that another function we have a conflict between many of the enumeration and many of the instructions inside a block. Group together things that change at the same time. If possible create container data structures so that a change involves a change of one.
If possible, group all of the changes that happen at the same time together. Never ignore errors. Presence of errors indicates that you don't understand your system well enough and therefore don't have a full control over it. An error can be major or minor but it anyway contributes negatively to the design and operation of your system and also to your understanding of it see Periphery. If a higher-level error wraps some other underlying error, the information about the underdying error shall not be lost.
Instead, it should be fully available to the higher-level error for error handling, logging, tracing, etc. Make a clear distinction between critical and non-critical errors on all levels: source code, software design, error reporting, documentation.
When there is no error handling, presence of asserts gives at least some basic guarantee that software does not do what it is not supposed to. Stable Components is a resort of a Maintenance Programmer. One way for a developer to survive in a large legacy project is to create stable components or extract them out of existing mess of code.
Stable component most likely means a testable component: it can be a parsing module or API layer or string manipulation helpers. Having such islands of stability helps a lot to overcome the difficulties of a maintenance programming. See also Periphery and Prima Materia Heuristics. If your code feels tricky, that's your gut telling you that something isn't right. Listen to your gut. If you find yourself thinking of a piece of code as a near trick, you're really saying to yourself that an algorithm produces correct results even though it is not apparent that it should.
The bugs won't be apparent to you either. Be truly clever; write boring code. As experts, they go through a checklist of criteria to find flaws which design teams overlooked. The Nielsen-Molich heuristics state that a system should:.
Our Contact page exemplifies the 8 th Nielsen-Molich Heuristic of showing only relevant information for current tasks.
However, like any method, there are pros and cons:. A vital point is that heuristic evaluation, however helpful, is no substitute for usability testing. Every product or website should be easy and pleasurable to use, but designing an effective, efficient and enjoyable product is hardly the result of good intentions alone.
Only through careful execution of certain usability principles can you achieve this and avoid user dissatisfaction, too. This course is designed to help you turn your good intentions into great products through a mixture of teaching both the theoretical guidelines as well as practical applications surrounding usability. Countless pieces of research have shown that usability is important in product choice, but perhaps not as much as users themselves believe; it may be the case that people have come to expect usability in their products.
This growing expectation puts even more pressure on designers to find the sweet spot between function and form. It is meanwhile critical that product and web developers retain their focus on the user; getting too lost within the depths of their creation could lead to the users and their usability needs getting waylaid.
Through the knowledge of how best to position yourself as the user, you can dodge this hazard.
0コメント