THE OBJECT TYPES ARE DEFINED FOR EACH DOMAIN AND MUST ALSO BE DEFINED IN THE DATABASE. If the catalog is to contain objects from a single schema, then an element of that type should be the only choice listed. If the catalog is to contain objects from different schemas, there should be an element reference to the object elements in each schema. The object elements can have the same names, but in that case, they should be from different namespaces - otherwise they are not different schemas. All of the query response object types based on one or more property filters use this group. The order of metadata properties included is based on the order of the filters in the query. Other than those where the occurrance restriction is unbounded will generally only have a single instance since they occur only once in the schema.