Relationships between people.

Family relationships and none professional relationships between people, are included in the common information model in two main ways:

1. An ontology of relationships, using relationship types and person relation subclasses, the latter being aligned with the Snomed-CT 'Person' class.
2. The data model, whereby a [related person] is linked to another person via a relationship type and relation entity, the latter being aligned with the above

As with the common information model in general, the two are related to each other so an enquirer can build sophisticated relationship queries and advanced family trees.

Relationships appear complex because of the way the terms are used in plain language

For example a "mother" is a type of person who is a mother of somebody. A son "has a mother" who is a mother. However, the same person who is a mother may also be a "sister" (whether or not the relationship to her sister has been authored. Consequently, there is a need not only to model the relationship between people (using a sub property of "related to"), but also to model the relation as a role independently of the relationship itself.

In addition a related person may or may not be a patient or person recorded in the record store. It may be someone unknown or abroad and there may be little information on them other than a contact detail. Therefore the related person also has to be modelled as an entity. This can be illustrated as follows:

Thus there are 4 potential entity types in a relationship

a) The source patient (the person who has the relationship)

b) The person who is the relation, acting in that role

c) Information about that person, which would be the same, whatever relation they were to other people

d) Another patient in the record store i.e. a full link between one person and another.

It is possible to model all links between people as relationships of this kind. However, in practice most relationships can be more direct e.g. the subject of an observation being a patient, or an encounter being performed by a doctor. In the common model these are modelled directly. Relationships of the kind modelled above are reserved for family relationships or non professional relationships such as carers.