Abstract
Designing assistive technological solutions for disabled and older people is fraught with problems because of the number of agencies involved. These problems are compounded by the lack of under-standing that can exist between the engineers and the health staff. This lack of understanding can develop into extreme delays in installing the technology, while the needs of the person with disabilities are subsumed in preference to ease of design and installation. Clearly, these potential misunderstandings could be ameliorated by improved communication between the widely different disciplines each with their own culture, ethos, knowledge and jargon. The CUSTODIAN Smart-House simulation software provides a focus for discussion on CUSTODIAN's development in relation to reliability and safety of systems design.