Wildcard elements terminologies

Wildcard element refers to the wildcard schema component, that is the XML schema element "any".

Replacement element is an element that will be used in instance documents as wildcard replacement contents, that is where the schema specifies a wildcard element.

Custom namespace is a namespace that is not defined in the main schema. The default namespace is defined in the main schema.

Custom prefix is a prefix for a custom namespace.

Custom schema is a schema where a custom namespace is defined. It is referenced from the instance document, not from the schema for the default namespace.