Modeling activities
Activities are "The activity of a patient/user, i.e. daily and nocturnal activities."
Activity has an activityKind (datatype property), and two sub-classes: s4ehaw:DailyActivity and s4ehaw:NocturnalActivity These sub-classes sound like kinds of activities actually.
Arguably the SAREF Core pattern for states cannot represent activities, but it may be appropriate that SAREF4EHAW defines a similar pattern for activities.