QuadSource <--> TripleSource conversion

[damooo]

Hello @pchampin , Currently it is possible to convert Graph <--> Dataset, But i cannot figure out how to convert a TripleSource <--> QuadSource at the streaming level, without loading statements into a Graph or DataSet respectively. At least if there is a method to convert ScopedRioSourceTriple <--> ScopedRioSourceQuad, it seems implementable outside for TripleSource<Triple = ScopedRioSourceTriple> and QuadSource<Quad = ScopedRioSourceQuad>.

It would be much useful if we can specify triplesource_fallback_graph_iri too for such conversion.

Thanks in advance for your help

[pchampin]

The original idea was that the following code would do the trick:

my_quad_source.map_quads(Quad::wrap_as_triple)

Indeed quad::stream::MapSource implements TripleSource if the passed closure produces Triples (see API doc).
Unfortunately, this does not work in the general case, because of some arcane lifetime issue :-/ My bad.

A workaround consist in writing your own function that copies the terms of the quad, e.g.:

fn q2t<Q: Quad>(q: Q) -> [BoxTerm; 3] {
    [q.s().copied(), q.p().copied(), q.o().copied()]
}

and then

let triple_src = quad_src.map_quads(|q| q2t(q));

Ultimately, I hope to get the example above working (the one using Quad:wrap_as_triple), but that may occur only in release 0.8.0, which will use GATs (see my blog post about this).

[damooo]

Thanks for that @pchampin .

I am trying for a parsing abstraction. As nested generics/assocciated-types getting too complicated for it, I am trying to zero-down to ScopedRioSourceTriple and ScopedRioSourceQuad as concrete types for TripleStreamingMode, QuadStreamingMode traits respectively as they are concrete types given by default parsers' quad-sources/triple-sources. Hence need to convert between ScopedRioSourceTriple <--> ScopedRioSourceQuad concretely. But there seems no public way to construct them. As i checked they have basic unit of RioTermWrapper, whose term field is private, and no other construction method. How should i handle this case?

[damooo]

Hello @pchampin, i do published a crate rdf_dynsyn, (source: @ github). This crate provides sophia-compatible and sophia-based rdf parsers/serializers, that can be instantiated against any of supported syntaxes dynamically at run time.

request feedback, as i am quite new to rust.

[pchampin]

I had a quick look at the documentation, and that looks really interesting 👍 I ran into the same issue when writing a simple CLI converter as an example of program using Sophia, but your approach is of course much cleaner and scalable.

I'll look at it in more detail when I find some time.