Hello Veronika,

Thank you for your very pragmatic tutorials, I feel like what I learnt can be easily transposed to my projects.

I had a couple of difficulties to make it through this second tutorial though, here are a couple of things I have noted:

• in The Quest for IRI section, I had to fill the prefixes as such in the following SPARQL queries in order to make them work:

  PREFIX def: <urn:maplib_default:>
  PREFIX rdf: <w3.org/1999/02/22-rdf-s…>
  PREFIX ast: <eurovotech.org/objects-…>

  PREFIX ast: <eurovotech.org/objects-…>
  
  SELECT ?planet
  WHERE { ?planet a ast:Planet }

• In Connecting Even More Data section:

  • it seems like there is a typo in the Polars data engineering steps: you first rename (alias) the column planet to planet_iri, but then, below, you select a planet_uri column that does not exist.

  • Then you load an instance named data I don’t know where it comes from which has a satellites() method:

    m.map_default(data.satellites(), “satellite_uri”)

    I tried to guess and corrected this way:

    m.map_default(df_satellites, "satellite_iri")

  • Then there is a new SPARQL query for which I modified this way in order to get the results:

    PREFIX def: <urn:maplib_default:>
    PREFIX ast: <eurovotech.org/objects-…>
    
    SELECT ?planet (COUNT(?moon) AS ?countMoon)
    WHERE {
        ?moon def:planet_iri ?p.
        ?p def:planet ?planet.
    }
    
    GROUP BY ?planet
    
    >>>
    ┌─────────┬───────────┐
    │ planet  ┆ moonCount │
    │ ---     ┆ ---       │
    │ str     ┆ u32       │
    ╞═════════╪═══════════╡
    │ Mars    ┆ 2         │
    │ Saturn  ┆ 61        │
    │ Pluto   ┆ 5         │
    │ Jupiter ┆ 67        │
    │ Neptune ┆ 14        │
    │ Earth   ┆ 1         │
    │ Uranus  ┆ 27        │
    └─────────┴───────────┘

• There are some weird quotes in the code of your first and second tutorials that hinder them to be immediately reproducible in an IDE: “ and ” .

Also, just a tip, to ease polars DataFrames visualization, there are configurable printing options. For example:

pl.Config.set_tbl_width_chars(width=1000)

pl.Config..set_fmt_str_lengths(200)

Best,