Well done sir! I am glad to finally see text like this.
I would start with concepts ("RDF resources") rather than the mechanics of
getting a project set up with an template Java file. At least that's me. As
soon as I say the first graph, I though "oh, I want to see that up front".
More of an API design question on the example:
System.out.println(alice.ntriplesString());
Why is the method not called toNtriplesString() or toNTriplesString()? What
does toString() do? Give me a "debug" string?
"*Note*: For simplicity this tutorial use *relative IRI references* which
are not really global identifiers. While this is supported by SimpleRDF,
some implementations will require *absolute IRIs* like <
http://example.com/Alice>."
It would like to know what the W3C standard says when I read text like the
above. In general I think it would be helpful to have a POV like "This text
adheres to the standard unless otherwise stated."
In this example:
<Alice> <knows> <Bob> .
What does the "." mean?
In the text:
You will get a compiler error:
RDFTerm cannot be converted to BlankNodeOrIRI
This and the follow up is confusing from a RDF novice POV. Starting by
describing an error makes understanding more difficult. Why do not a
"correct" walkthrough _fisrt_ instead of _starting_ with an error. Then at
the end, you can say, if you tried X, you'd get an error. By that point, it
will either be obvious to the reader or just a side note.
When I see:
- The *subject* must be a BlankNodeOrIRI
<https://commonsrdf.incubator.apache.org/apidocs/org/apache/commons/rdf/api/BlankNodeOrIRI.html>,
that is either a BlankNode or IRI
- The *predicate* must be a IRI
<https://commonsrdf.incubator.apache.org/apidocs/org/apache/commons/rdf/api/IRI.html>
(so
we can look up what it means)
- The *object* must be a RDFTerm
<https://commonsrdf.incubator.apache.org/apidocs/org/apache/commons/rdf/api/RDFTerm.html>,
that is either a BlankNode, IRI or Literal
I want to see a diagram (maybe UML) that shows, if or how these types
relate to each other.
Again, more of an API design question:
if (! (aliceFriend instanceof BlankNodeOrIRI)) {
continue;
}
This feels hacky and at least needs a clarification:
- If something is not a BN or IRI, is it always a Literal?
- Why not have methods like isLiteral(), isBlankNode() and isIRI() that is
implemented in all the right places.
I think RDFTerm is the root interface but I am not 100% sure without
looking at the Javadoc. I'd like to have this made obvious in the text (see
above WRT a diagram).
I'd like an explanation on whether I can or cannot do:
Literal aliceRating = rdf.createLiteral(13.37f, Types.XSD_FLOAT);
That's 13.37f as opposed to "13.37".
As above, tells me if I can be more OO and say:
Literal footballInEnglish = rdf.createLiteral("football", Locale.ENGLISH);
I just skimmed through the rest, out of time, sorry.
Gary
On Mon, Nov 21, 2016 at 6:09 AM, Stian Soiland-Reyes <[email protected]>
wrote:
> As raised in the recent vote, Commons RDF could do with an
> introduction to RDF for people who have not used RDF before. The API
> should be quite suitable for RDF beginners, as unlike say Jena or
> Sesame they should not be so easily overwhelmed by the API size.
>
>
> Here's my first attempt at such a tutorial:
> http://commonsrdf.incubator.apache.org/introduction.html
>
>
> Feedback welcome - particularly from Commons folks who don't know too
> much about RDF!
>
>
> Note that this tutorial does not yet go into the crucial part of
> loadinh/save of RDF files, as that involves using the other RDF
> implementations, which would require use of Maven for dependencies. I
> thing a second tutorial could cover that aspect.
>
> --
> Stian Soiland-Reyes
> http://orcid.org/0000-0001-9842-9718
>
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