A health information system (HIS)must be arranged so as to be useful for widely different circumstances of care. These include information processing where requirements have different timing requirements, levels of detail, need for readiness of access, etc. a. For anticipatory screening to prevent illness and disability and to achieve improved personal health as well as to recognize and control early disease resk factors. b. For periodic and episodic acute or short term care designed to remedy or cure illnesses and injuries. This may involve management of life threatening situations. Data access is almost unpredictable in respect to whom and when. c. For comprehensive, continuing, or extended care (often called “long term”), where the purpose is to restore healthful status or to achieve rehabilitation or restoration of function. Predictability of usage is high and repetitive. Extended life maintaining services may have to be aided when the original medical condition is incurable or unavoidable as can occur with advanced age, etc. In this circumstance it is crucial that the system assist in achieving comprehensiveness and continuity. d. For population health educational purpose largely directed toward better personal health practices preserving the capacity to cope with illness and disability. Here, generality of data usage and elective usage of data is common.