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312 12 Building Bioinformatics Ontologies

</owl:Restriction>

<rdfs:subClassOf>

</owl:Class>

This constraint requires that at least one authorization of the admission

must be by a doctor. However, there could be multiple authorizations of

the same admission, and some of them could be by staff members who

are not doctors. To constrain all of the authorizations for a particular ad-

mission to be by doctors, one should useowl:someValuesFromas in

the previous section.

2. owl:minCardinality.This restricts the number of values that a property
   can have. For example, if every admission must be authorized, then spec-
   ify the following:

<owl:Class rdf:about="#Admission">

<rdfs:subClassOf>

<owl:Restriction>

<owl:onProperty rdf:resource="#authorizedBy"/>

<owl:minCardinality

rdf:datatype="&xsd;nonNegativeInteger"

>1</owl:minCardinality>

</owl:Restriction>

<rdfs:subClassOf>

</owl:Class>

3. owl:maxCardinality.This is the reverse of a minimum cardinality restric-
   tion. It specifies the maximum number of values.


4. owl:cardinality.This is equivalent to two restrictions: a minimum and a
   maximum, both specifying the same number. For example, if every event
   should be authorized by exactly one staff member, then use the following:

<owl:Class rdf:about="#Admission">

<rdfs:subClassOf>

<owl:Restriction>

<owl:onProperty rdf:resource="#authorizedBy"/>

<owl:cardinality

rdf:datatype="&xsd;nonNegativeInteger"