Serializer accepts invalid Turtle syntax as input and outputs invalid RDF

[rjyounes]

The serializer accepts the following as input:

@prefix ex: <https://example.org/> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix xs: <http://www.w3.org/2001/XMLSchema#> .

ex:Person
	a owl:Class ;
	skos:prefLabel: "Person"^^xs:string ;
	.

and outputs the following invalid RDF/XML:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rdf:RDF [
	<!ENTITY ex "https://example.org/">
	<!ENTITY owl "http://www.w3.org/2002/07/owl#">
	<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">
	<!ENTITY rdfs "http://www.w3.org/2000/01/rdf-schema#">
	<!ENTITY skos "http://www.w3.org/2004/02/skos/core#">
	<!ENTITY xs "http://www.w3.org/2001/XMLSchema#">
]>
<rdf:RDF
	xmlns:ex="https://example.org/"
	xmlns:owl="http://www.w3.org/2002/07/owl#"
	xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
	xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
	xmlns:skos="http://www.w3.org/2004/02/skos/core#"
	xmlns:xs="http://www.w3.org/2001/XMLSchema#">
	
	<owl:Class rdf:about="&ex;Person">
		<skos:prefLabel: rdf:datatype="&xs;string">Person</skos:prefLabel:>
	</owl:Class>

</rdf:RDF>