this class memorize a type specification, which may be
 - a class reference
 - an explicit type
Declaration :
Directly inherited by : UmlTypeSpec
Artifact : UmlBaseTypeSpec
| Operation UmlBaseTypeSpec | 
Declaration :
| Operation toString | 
returns the type as a string in all cases
Declaration :
| Operation clone_it | 
Clone the type specification, defined only in Java which does not have 'const' or 'value passing'
Declaration :
| Attribute explicit_type | 
significant in case type == 0
Declaration :
| Relation type (<unidirectional association>) | 
Declaration :