## Defining indexes

It may be the case that SPARQL queries performed on the endpoint are known to match, sort, or filter on certain properties more often than others. In this case, the ontology may use tracker:domainIndex in the class definition:

    # Make queries on ex:dateOfBirth faster
    ex:Mammal a rdfs:Class;
              rdfs:subclassOf ex:Animal;
              rdfs:comment "A mammal";
              tracker:domainIndex ex:dateOfBirth.

Classes may define multiple domain indexes.

Be frugal with indexes, do not add these proactively. An index in the wrong place might not affect query performance positively, but all indexes come at a cost in disk size.