The object can be either a value or a resource. 

 * Isn't it true that both literals and resources can have a language
   tagging?

 * Isn't it true that a literal IS a internal resource that can be
   referred to by many statements? Those records in the table would
   have both a name (URI) and a value (literal)


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The compact XML serialization of RDF in
http://www.w3.org/TR/PR-rdf-schema/
states that Literal is subClassOf Resource.
But this is missing in the basic XML serialization.


This may be an error. Even a literal can be represented with a resource,
but then that would not be a literal from the RDF point of view.


The Schema specification messes things up. All literals is of the
type Literal. That is (type, s, Literal). This go against the M & S,
that says that the subject can't be a literal.

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I wonder:

How do you represent each obj in say a relational database?

http://www.w3.org/TR/REC-rdf-syntax/ says:

  The xml:lang attribute may be used as defined by [XML] to 
  associate a language with the property value. There is no 
  specific data model representation for xml:lang (i.e., it 
  adds no triples to the data model); the language of a 
  literal is considered by RDF to be a part of the literal.



object is either a resource or a literal. So we have to mark every
object to determine if it is a literal or a resource. And each literal
can be anything. XML can be used to determine its language, the type of
data, etc. How can it be stored?

And predicate should be stored as a record with one namespace URL and
one name.



Isn't there any model of how to represent bags, types, subclass, etc in
an efficient way?  How can RDF be sayed to be implemented without, for
example, a correct handling of the rdf:value propertie?