A problem observation (templateId 2.16.840.1.113883.10.20.1.28) SHALL be represented with Observation. The value for "Observation / moodCode" in a problem observation SHALL be "EVN" 2.16.840.1.113883.5.1001 ActMood STATIC. A problem observation SHALL include exactly one Observation / statusCode. The value for "Observation / statusCode" in a problem observation SHALL be "completed" 2.16.840.1.113883.5.14 ActStatus STATIC. A problem observation MAY contain exactly one problem status observation. The template identifier for a problem status observation is 2.16.840.1.113883.10.20.1.50. A problem observation MAY contain exactly one problem healthstatus observation. The template identifier for a problem healthstatus observation is 2.16.840.1.113883.10.20.1.51. A problem observation MAY contain exactly one patient awareness. A problem observation SHOULD contain exactly one Observation / effectiveTime, to indicate the timing of condition (e.g. the time the condition started, the onset of the illness or symptom).