Methodology stages and involved submodels. Observation phase identifies the problems to address in the assistive system. Planning phase consists of (a) formal problem definition, (b) description of results to achieve, and (c) collecting background literature. Design stage obtains the design guidelines to create the assistive system. Development phase corresponds to the implementation of the system. Base-line stage collects information to deploy the initial trials. Execution phase gathers feedback from end users improving next evaluation stages. Evaluation phase assesses the suitability of the analysis system. The last three stages comprise the evaluation circle.