On Fri, May 31, 2019 at 08:02:03PM +0200, Thomas Tanon wrote: > Hi James, > > I'm not the best person to answer your questions (I've never actually used > ShEx or contributed to it) but I hope to be able to answer your questions. > > > I'm not clear whether there is an RDF representation of ShEx that could > be added to WDQS -- this is a point that would be useful to clarify; > and, if not, whether work is going on in this direction. > > TL;DR: yes but it does not seem much used at the moment. > > ShEx specifies [1] two syntaxes, ShExC that is the "plain text" syntax used > on Wikidata and ShExJ that is based on JSON-LD. JSON-LD beeing an RDF > seralization, there is indeed an RDF representation of ShEx. To get plain > triples one could use the JSON-LD to RDF triples conversion algorithm that > is implemented in most JSON-LD libraries. The old ShEx documentation pages > refers to a ShExR serialization of ShEx to RDF but I believe it has been > dropped in favor of ShExJ+JSON-LD to RDF conversion.
We actually do test the ShExR with a Turtle representation. We have ~500 round-trip tests between the three representations: <https://github.com/shexSpec/shexTest/tree/extends/schemas> It would be pretty easy to add a translation to RDF in the backend of a schema update. That would give you all the clever meta queries you'd like for dependency-checking and auditing without making people edit triples. > > It's not immediately clear to me whether SHACL adapts easily to > memberships defined by eg P31 "instance on" or P279 "subclass of" > statements, etc; also memberships possibly further defined or limited by > other statements. > > Indeed Shacl 1.0 does not seem to be able to express it. There is an > extension [1] that allows to specify targets using a sparql query, just > like what is done with the ShEx playground using the focus nodes sparql > query. > > Thomas > > [1] http://shex.io/shex-semantics/ > [2] > https://www.w3.org/2018/jsonld-cg-reports/json-ld-api/#deserialize-json-ld-to-rdf-algorithm > [3] https://www.w3.org/TR/shacl-af/#SPARQLTarget > > Le ven. 31 mai 2019 à 11:06, James Heald <jpm.he...@gmail.com> a écrit : > > > On 30/05/2019 17:45, Benjamin Good wrote: > > > I'd like to restate the initial question. > > > > > > Why did wikidata choose shex instead of other approaches? > > > > > > From this very detailed comparison > > > http://book.validatingrdf.com/bookHtml013.html (thank you Andra!) I > > could > > > see arguments in both directions. I'm curious to know what swayed the > > > wikidata software team as my group is currently grappling with the same > > > decision. > > > > > > > > > One of the key differences would seem to be that SHACL has been > > deliberately constructed to directly representable in RDF -- so a SHACL > > expression could be put straight into WDQS and made queryable for what > > it pertains to. > > > > I'm not clear whether there is an RDF representation of ShEx that could > > be added to WDQS -- this is a point that would be useful to clarify; > > and, if not, whether work is going on in this direction. > > > > IMO, it would be a very important asset to be able to query the Shape > > specifications using SPARQL -- querying not for compliance, but for what > > the specifications actually contain. > > > > > > > > On the other hand, SHACL seems very strongly based on shapes for members > > that are connected by an "is a" relationship. > > > > It's not immediately clear to me whether SHACL adapts easily to > > memberships defined by eg P31 "instance on" or P279 "subclass of" > > statements, etc; also memberships possibly further defined or limited by > > other statements. > > > > It would seem a basic requirement, but I didn't see it on a first quick > > skim-read. > > > > -- James. > > > > _______________________________________________ > > Wikidata mailing list > > Wikidata@lists.wikimedia.org > > https://lists.wikimedia.org/mailman/listinfo/wikidata > > > _______________________________________________ > Wikidata mailing list > Wikidata@lists.wikimedia.org > https://lists.wikimedia.org/mailman/listinfo/wikidata _______________________________________________ Wikidata mailing list Wikidata@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata
