What are different user interface design principles and guidelines in software engineering ?

A good web application interface is understandable and forgiving, providing the user with a sense of control. The inner workings of the system are not for concern for the users. Effective applications perform a maximum of work, while requiring a minimum of information from users.

USER INTERFACE DESIGN PRINCIPLES AND GUIDELINES

- Consistency of actions should be required in similar situations. The use of navigation controls, menus, icons should be consistent throughout the web application.
- Anticipation Web application should be designed in such a way that it should interpret the user's next move.
- Communication Whatever activity that is been initiated by the user, it should be communicated by the interface. Communication can be obvious or subtle. User status and location should also be communicated by the interface.
- Efficiency Users work efficiency should be optimized by the design of the web application and its interface and not the efficiency of the web engineer who designs and builds it.
- Flexibility Flexibility of the user interface should enable some users to get the tasks done directly and some other users to explore the web application in random fashion.
- Controlled Autonomy User movement should be facilitated by the interface in such a manner that enforces navigation conventions that are established for application.
- Focus The interface of the web application should be focussed on user tasks at hand.
- Human Interface Objects Use reusable human interface objects. An interface object that is seen, heard, touched by the end user can be get from the object libraries.
- Learn ability Learning time should be reduced by a well designed web application interface.
- Latency Reduction The web application should use multitasking so that the user can proceed with his work and do not wait for some internal operation to get completed.
- Metaphors A metaphor should call images and concepts from user's experience, but it does not need to be an exact reproduction of real world experience. The web application interface that uses an interaction metaphor is easier to learn and use.
- Maintain work product integrity A work product must be automatically saved so that there is no loss of information if an error occurs.
- Readability Every person should be able to read the information in the user interface.
- Track State The state of the user interaction should be saved and stored so that the user can return to the same point even if he or she logs off.
- Visible navigation A well designed web application interface provides the illusion that users are in the same place, with the work brought to them.

Overview of Soak testing.

Soak testing is running a system at high levels of load for prolonged periods of time. A soak test would normally execute several times more transactions in an entire day than would be expected in a busy day, to identify any performance problems that appear after a large number of transactions have been executed. Also, it is possible that a system may stop working after a certain number of transactions have been processed due to memory leaks or other defects. Soak tests provide an opportunity to identify such defects, whereas load tests and stress tests may not find such problems due to their relatively short duration.A soak test would run for as long as possible, given the limitations of the testing situation. For example, weekends are often an opportune time for a soak test.

There are some typical problems identified during soak tests are:
- Serious memory leaks that would eventually result in memory crisis.
- Failure to close connections between tiers of a multi-tiered system under some circumstances which could stall some or all modules of the system.
- Failure to close database cursors under some conditions which would eventually result in the entire system stalling.
- Gradual degradation of response time of some functions as internal data structures becomes less efficient during a long test.

Apart from monitoring response time, it is also important to measure CPU usage and available memory. If a server process needs to be available for the application to operate, it is often worthwhile to record its memory usage at the start and end of the soak test. It is also important to monitor internal memory usages of facilities such as Java virtual machines, if applicable.