langchain.graph RDFGraph does not read OWL

[Caitlin2694]

System Info

langchain verion: 0.0.237
python version: 3.11.4

Who can help?

@hwchase17

When loading an OWL graph in the following code, an exception occurs that says: "Exception has occurred: KeyError 'op'". It appears that RFGraph class is having trouble with the owl standard specifically.

graph = RdfGraph(
    source_file="example.ttl",
    serialization="ttl",
    standard="owl"
)

I found this issue when using RDFGraph within the GraphSparqlQAChain class

Thank you very much for your help.

Information

• The official example notebooks/scripts
• My own modified scripts

Related Components

• LLMs/Chat Models
• Embedding Models
• Prompts / Prompt Templates / Prompt Selectors
• Output Parsers
• Document Loaders
• Vector Stores / Retrievers
• Memory
• Agents / Agent Executors
• Tools / Toolkits
• Chains
• Callbacks/Tracing
• Async

Reproduction

Steps to reproduce:

1. Use the following code

from langchain.chains import GraphSparqlQAChain
from langchain.graphs import RdfGraph

graph = RdfGraph(
    source_file="example.ttl",
    serialization="ttl",
    standard="owl"
)

graph.load_schema()

print(graph.get_schema)```

2. Use the following graph

@prefix : <http://example.org/pump-ontology#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@base <http://example.org/test-ontology> .

<http://example.org/test-ontology> rdf:type owl:Ontology .

:hasTopping rdf:type owl:ObjectProperty .
:Object rdf:type owl:Class .
:Pizza rdf:type owl:Class ;
       rdfs:subClassOf :Object .
:Topping rdf:type owl:Class ;
         rdfs:subClassOf :Object ,
                         [ rdf:type owl:Restriction ;
                           owl:onProperty :hasTopping ;
                           owl:someValuesFrom :Topping
                         ] .

Expected behavior

For the graph to load and for graph.get_schema to produce the classes (Pizza and Topping) and object property (hasTopping) in the class.

[dosubot]

Answer generated by a 🤖

Answer

I understand that you're encountering an issue with the RdfGraph class in the LangChain framework when trying to load an OWL graph. The error message you're seeing, "Exception has occurred: KeyError 'op'", suggests that there's a problem with how the load_schema method is handling the OWL standard.

From your description, it seems that the issue lies in the load_schema method of the RdfGraph class. When the standard is set to "owl", the same query (cls_query_owl) is being used to fetch classes, object properties, and data properties. This could be the root cause of the KeyError 'op' exception, as the cls_query_owl query does not return a column named 'op'.

Here's the part of the code that appears to be causing the problem:

elif self.standard == "owl":
    clss = self.query(cls_query_owl)
    ops = self.query(cls_query_owl)  # This should be op_query_owl
    dps = self.query(cls_query_owl)  # This should be dp_query_owl
    ...

To address this issue, you could modify the code as follows:

elif self.standard == "owl":
    clss = self.query(cls_query_owl)
    ops = self.query(op_query_owl)  # Corrected
    dps = self.query(dp_query_owl)  # Corrected
    ...

This modification should resolve the issue by using the correct queries (op_query_owl and dp_query_owl) to fetch object properties and data properties, respectively.

Please note that this is a potential solution based on the information provided. If this solution works for you and you believe it's a bug that could impact other users, I encourage you to make a pull request with this change. If this solution doesn't align with your experience or if the issue persists after trying this solution, I recommend checking if you're using the latest version of LangChain, as the issue might have been addressed in a more recent update.

Sources

• langchain/graphs/rdf_graph.py

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[Caitlin2694]

Fixed and merged. Thanks all!