rdf:type is not considered a relation for SPARQL queries
SPARQL query:
">SELECT ?page ?rel ?obj
WHERE {
?page ?rel ?obj .
}
</pl>```
should list all triples in the wiki, but it does not list the category statements (`page a category .`).
To gather them, one should prepare a query that ask especially for them:
```<pl format="sparql">
SELECT ?page ?obj
WHERE {
?page a ?obj .
}
</pl>```
It is a bug, because category statements should be listed by the first query.