SHEL(L) Model

Model are used to understand human factor  as a framework around which human factor issues can be structured.

SHEL(L),PEAR, Dirty Dozen 

S - Software
H - Hardware
L - Liveware
E - Environment                                      

 Liveware is at the center of the model, is  the most critical and flexible component in the working Environment and subject to considerable variations in performance and suffer many limitations.                          

  1. Physical size and shape. In the design of workplace and equipment, body measurements and movements is considerd , which may vary according to factors such as age, ethnicity and gender. Human Factors inputs is provided  in the design process, and data for these inputs are available from anthropometry, biomechanics and kinesiology.                                            
  2. Physical needs. People's requirements such as for food, water and oxygen are indicated in human physiology and biology
  3. Input characteristics. Humans possess various sensory systems for collecting information from the world external as well as internal to them, enabling them to respond to events and to carry out the required task. All senses is subjected to degradation for one reason or another, and the sources of knowledge include psychology and physiology                                            
  4. Information processing.  human functions have limitations. Poor instrument and alerting system design has frequently resulted from a failure to take into account the capabilities and limitations of human information processing. Factors such as stress, motivation and short- and long-term memory are involved. Psychology and cognitive sciences are the sources of background knowledge here.
  5. Output characteristics. Once information is sensed and processed, decisions are made and/or messages are sent to muscles to initiate the desired response. Responses may involve a physical control movement or the initiation of some form of communication. Acceptable control forces and direction of movement have to be known, and biomechanics, physiology and psychology provide the background knowledge.
  6. Environmental tolerances. Environmental factors such as temp, vibration, pressure, humidity, noise, time of day, amount of light and G-forces can affect human performance and well-being. Heights, enclosed spaces and a boring or stressful work environment can influence human behaviour and performance. Background information is available from medicine, psychology, physiology and biology.
       Liveware is the hub of the SHEL model. The remaining component must be adapted to and match with this central component.      

Interface 

  1. Liveware-Hardware interface of human-machine systems: the design of seats to fit the sitting characteristics of the human body;   displays to match the sensory and info. processing characteristics of the user;  controls with proper movement, coding and location.   
  2. Liveware-Software. Interface between humans and the non-physical aspects of the system. (procedures, manual and checklist, symbology and computer program. 
  3.  Liveware-Environment. How the human react to environment.                                    (a) Measures taken aimed to adapting the human to the environment (using helmets, flying suits, oxygen masks and G suits).                                                             (b) Alter the environment to match human requirements ( pressurization, air conditioning and soundproofing).
  4. Liveware-Liveware. This is the interface between people. 

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