Relationships between people.

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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 a 'relation' as subclass of related person, the latter being aligned with the Snomed-CT 'Person' subclasses with additions for in-laws.The ontology properly defines relationships and relations.
  2. The data model, whereby a [related person] is linked to another person via a relationship type, 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.

Example of a relationship. The related person {Mary} is both the mother of {Fred}, and the Sister of {Helen}. 'is mother of' is modelled as an inverse property of 'has mother'..

Relationships appear complex to model because of the ambiguous way the terms are used in plain language.

For example a "mother" is a 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. The ontology resolves this difficulty as follows:

By building up simple family tree relations (parent, child etc), it is possible both to deduce relations, and relationships, including the relations that people struggle to remember.  Most people would struggle with understanding who their third cousins were, yet they are genetically quite close. A third cousin is defined as a child of one's parent's second cousin, or perhaps more precisely, a great grandchild of a great grandparent's sibling! Anyone capable of remembering this, is probably a genealogist.

Within the data model, the two entities involved are the patient and the related person, and the relationship between them "has related person/ is relation of " subtype. Within the ontology, relations are defined as subclasses of related person by dint of the relationships they have to other people.

Thus it is possible to deduce that Mary is a mother and a sister simply by noting the relationship as part of a family tree.

Example of a property chain. (is sister of -> is mother of) is a subproperty of> is aunt of.

Relations are more complex when chained together. Common parlance is to use an abbreviated term to name a once removed relationship. In the above example, Helen is an Aunt to Fred. Once again the ontology defines this by the use of property chains.

A third cousin can equally be defined as a sub property of " has Great Grand Parent - > is Sibling Of - > is Great Grand Parent Of" and this is indeed modelled in the ontology in case anyone might need it.