Limitations and troubleshooting

Limitations

DataFrame conversion

The DataFrame conversion has these limitations:

rumo does not escape quotes or backslashes in strings. A string with a " character gives Turtle that is not correct.
rumo writes column names directly as property names. A column name with a space or a special character gives Turtle that is not correct.
rumo writes a null value as an empty string "". Thus, a rule finds a value for each cell, also for a cell with no data.

To prevent these problems, clean the DataFrame before you load it. For example, rename the columns and remove the null values.

Other limitations

Rumo.run keeps the Python global interpreter lock (GIL) during the run. Other Python threads stop until the run is complete.
Rumo.run does not write the files of @export statements. To write these files, use the command-line tool.
The describe, print_info and to_turtle functions accept only Polars DataFrames.

Troubleshooting

Problem	Possible cause	Action
A predicate has no facts.	The rules do not find the data.	Make sure that the resource name in `@import` is the same as the `resource` argument.
A predicate has no facts.	The IRIs in the rules are different from the IRIs in the data.	Make sure that the `@prefix` of the rules is the same as `base_url`.
A comparison with a number fails.	The value is an `xsd:decimal`.	Use `DOUBLE(?x)` in the rule.
`RuntimeError: Unknown predicate`	The predicate name in `predicates` is not in the rules.	Correct the predicate name.
`ValueError: no rules loaded`	You did not load a rule program.	Use `rules`, `rules_file`, `read_rules_str` or `read_rules_file`.
`ValueError: results contain several predicates`	You did not give a predicate name.	Give the predicate name, for example `to_pandas("good")`.
`ImportError` from `to_pandas`	pandas is not installed.	Install pandas: `pip install pandas`.
`rumo rules` shows "Rule support is not enabled".	The binary does not have the `rules` feature.	Build again with `--features rules`.