The primary purpose of XML Schemas is to declare vocabularies.
These vocabularies can be identified by a namespace that is specified in the targetNamespace attribute.
Not all XML Schemas will have a targetNamespace.
Many XML Schemas define vocabularies that are reused in another XML Schema.
Possible targetNamespace declarations include the following:
targetNamespace="http://www.rntsoft.com/name"
xmlns:target="http://www.rntsoft.com/name">
or
targetNamespace="http://www.rntsoft.com/name"
xmlns="http://www.rntsoft.com/name">
In the first declaration, the element uses the default namespace.
Because of this the target namespace http://www.rntsoft.com/name requires the use of a prefix.
In the second declaration, the element requires the use of a prefix.
Because the target namespace http://www.rntsoft.com/nameis using a default namespace declaration.