'xml' prefix is ​​not omitted when generating a DTD subset in a file formatted as sorted RDF/XML

[przemekgradzki]

The xml prefix is omitted when writing namespace declarations to the root element:

rdf-toolkit/src/main/java/org/edmcouncil/rdf_toolkit/writer/SortedRdfXmlWriter.java

Line 237 in 2603921

if ((USE_GENERATED_PREFIXES || !generatedNamespaceTable.containsKey(prefix)) && !"xml".equals(prefix)) {

but is not omitted when writing a DTD subset:

rdf-toolkit/src/main/java/org/edmcouncil/rdf_toolkit/writer/SortedRdfXmlWriter.java

Line 213 in 2603921

if (USE_GENERATED_PREFIXES || !generatedNamespaceTable.containsKey(prefix)) {

---

As a consequence, the result of the operation:

rdf-toolkit/docs/RdfFormatter.md

Line 98 in 2603921

6. Format a Turtle file (`input.ttl`) as sorted RDF/XML (`output.rdf`), using entity references for URL shortening

executed with the command:

java -cp target/rdf-toolkit-1.14.2.jar org.edmcouncil.rdf_toolkit.RdfFormatter \
  -s src/test/resources/ontologies/literal/test1.ttl \
  -tfmt rdf-xml -dtd

is the file containing the entry <!ENTITY xml "http://www.w3.org/XML/1998/namespace">:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rdf:RDF [
	<!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 xml "http://www.w3.org/XML/1998/namespace">
	<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#">
]>
<rdf:RDF
	xmlns="https://example.com/test1#"
	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:xsd="http://www.w3.org/2001/XMLSchema#">
	
	<owl:Ontology rdf:about="https://example.com/test1">
	</owl:Ontology>
	
	<owl:Class rdf:about="https://example.com/test1#ClassA">
		<rdfs:label>label1</rdfs:label>
		<rdfs:label xml:lang="en">label2</rdfs:label>
		<rdfs:label xml:lang="pl">label3</rdfs:label>
		<rdfs:label>label4</rdfs:label>
		<rdfs:label rdf:datatype="&xsd;token">label5</rdfs:label>
		<rdfs:label>label6</rdfs:label>
	</owl:Class>

</rdf:RDF>

If you reapply the RDF/XML formatting operation to the resulting RDF/XML formatting using entity references for URL shortening:

java -cp target/rdf-toolkit-1.14.2.jar org.edmcouncil.rdf_toolkit.RdfFormatter \
  -s src/test/resources/ontologies/literal/test1.ttl \
  -tfmt rdf-xml -dtd | \
  java -cp ./target/rdf-toolkit-1.14.2.jar org.edmcouncil.rdf_toolkit.RdfFormatter \
    -sfmt rdf-xml \
    -tfmt rdf-xml -dtd

is the file without the entry <!ENTITY xml "http://www.w3.org/XML/1998/namespace">:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rdf:RDF [
	<!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 xsd "http://www.w3.org/2001/XMLSchema#">
]>
<rdf:RDF
	xmlns="https://example.com/test1#"
	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:xsd="http://www.w3.org/2001/XMLSchema#">
	
	<owl:Ontology rdf:about="https://example.com/test1">
	</owl:Ontology>
	
	<owl:Class rdf:about="https://example.com/test1#ClassA">
		<rdfs:label>label1</rdfs:label>
		<rdfs:label xml:lang="en">label2</rdfs:label>
		<rdfs:label xml:lang="pl">label3</rdfs:label>
		<rdfs:label>label4</rdfs:label>
		<rdfs:label rdf:datatype="&xsd;token">label5</rdfs:label>
		<rdfs:label>label6</rdfs:label>
	</owl:Class>

</rdf:RDF>

[ElisaKendall]

@przemekgradzki @mereolog As far as I am concerned, the XML entity declaration can be omitted in both cases. It is not necessary and I would prefer that we leave it out altogether, regardless of which choice for retaining or eliminating the rest of the declarations.