Bug: Comparison and arithmetic on xsd:duration

[cmdoret]

It seems that comparisons (<,<=, ==, >=, >) and arithmetic operations (+,-) on xsd:duration in SPARQL queries always evaluate to null. Is this a bug?

Example:

data="""
@prefix ex: <http://example.org/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix schema: <https://schema.org/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .


ex:d1 ex:lasted "P6D"^^xsd:duration .
ex:d2 ex:lasted "P4D"^^xsd:duration .
"""
g = Graph().parse(data=data)
print(g.query("""
  SELECT ((?d1 - ?d2) AS ?delta)
  WHERE {
    ex:d1 ex:lasted ?d1 .
    ex:d2 ex:lasted ?d2 .
  }
""").serialize(format='csv').decode())

Observed output:

delta
""

Expected output:

delta
"P2D"^^xsd:duration

Do I understand correctly that conversion between xsd:duration and python types has not yet been added (e.g. here)?

If so, maybe I coud give it a shot, but I am not familiar with the codebase and don't fully appreciate the complexity of adding such support.

Environment:

• python 3.10.6
• rdflib 7.0.0

[WhiteGobo]

This seems like a bug. But i think that the problem is located in the sparql-plugin not with term.py

As far as i know, xsd:duration and other time related stuff is converted in python types of datetime and of isodate depending on the value. But those conversions are not always realiable because types isodate arent always compatible with types of datetime. Also isodate, which is used for the conversion, doesnt seem to be maintained anymore.

You can check if a conversion was used with the attribute value(checked with rdflib 7.0.0):

Literal("P6D", datatype=XSD.duration).value
>>> datetime.timedelta(days=6)