Systems and methods for maintaining cardinality schema to prevent corruption in databases indifferent to cardinality

A facility maintains a cardinality schema to manage indications of property cardinality on behalf of a database such as a graph database that is indifferent to the cardinality of properties stored within it. The facility can add cardinality indications to the cardinality schema for a property based on (1) semantics used to refer to one or more values of the property in an update request, (2) the number of values specified for the property in an update request, or (3) an explicit client declaration of the property's cardinality. Where a query or update request against the database uses cardinality semantics for a property that are inconsistent with the cardinality schema's indication for the property, the facility can reject the query or update request. The facility can also use the cardinality schema to automatically complete incomplete queries using the proper cardinality semantics for each involved property.