json-ld

Would be supercool to have "BlogPosting" as article JSON-LD type.

From the Google Docs (https://developers.google.com/search/docs/data-types/article#non-amp):

Article objects must be based on one of the following schema.org types: Article, NewsArticle, BlogPosting. (https://schema.org/BlogPosting)

I tried to use "BlogJsonLd" as type for Blogposts, but the Google Rich Result Test (https:

I believe turtle does not handle quads, but our default serialization format for ConjunctiveGraph is turtle as turtle does not override the default for Graph, I guess we should probably change this, question is to what.

I think TriG would make most sense, but the other option is n3.

Describe the feature

I'm not 100% sure we actually get this from our data source but it would be nice having a program-accessible constant that refers to the Schema.org version that the code is currently using.

I'm submitting a

• [x ] bug report.

Current Behaviour:

After #249
Trying to run tests with pytest tests/rdf_tests/test_rdf_basic.py -k test_rdf_runner -s, you get a report file with all the tests run.
Some tests return errors, for example:

{
    "Basic - Term 7": {
        "input": "basic/data-4.ttl",
        "query": "basic/term-7.rq",
        "error": "Expected {Sele