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Usability  > User-Centered Design Steps > Step 4 - 4 of 6
 
 


Step 4 - Allocate Functions

Function allocation is the distribution of the functions identified in STEP 3 to humans, hardware, software, or combinations, thereof.  Using the Human Role Strategy from STEP 2 as a basis, functions are assigned by comparing performance capabilities and limitations between humans and technology on parameters such as accuracy, speed, reliability, response flexibility, and strength.  Cost factors and user cognitive and affective support needs are also considered.  The following are sub-steps in the function allocation process.

  • Mandatory allocations.  Organizational policy, regulations, or statutes may require some functions to be performed by humans, or some functions may have been allocated to the "human-side" by the Human Role Strategy definition.  Already allocated, mandatory functions are reassessed and modified, if necessary.  Unallocated mandatory functions are assigned to human(s), equipment, or combinations of both.  For mandated human functions, the knowledge, skills, and abilities (KSAs) required for performance are identified.

  • Create alternate allocations of remaining functions.  Remaining functions are distributed between human(s), equipment, or combinations of both. This distribution is based upon ability to perform, utility or cost estimate, user cognitive support needs, frequency, workload, staffing and other considerations.  More than one allocation may be possible for some functions.  In this event, alternative allocations are developed.  When all functions have been addressed, user KSAs are refined in view of additional functions assigned.

  • Select optimal allocation.  For functions for which there are alternate allocations, select the optimal allocation by comparing risk/feasibility, performance time and accuracy, workload and staffing impact, training and life-cycle costs.

When all functions are allocated, Step 5 - Task Design and Analysis can commence.

  
 

 
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