- From: Gregg Kellogg <gregg@greggkellogg.net>
- Date: Wed, 20 May 2015 16:08:06 -0700
- To: David Booth <david@dbooth.org>
- Cc: "henry.story@bblfish.net" <henry.story@bblfish.net>, ahogan@dcc.uchile.cl, semantic-web@w3.org
> On May 20, 2015, at 2:55 PM, David Booth <david@dbooth.org> wrote: > > Hi Gregg, > > On 05/20/2015 05:07 PM, Gregg Kellogg wrote: > [ . . . ] >> Using a PATCH, you can’t reference existing BNodes. You _might_ be >> able to in an UPDATE, as I indicated. A PATCH is typically described >> as a series of deletes and adds (depending on the particular format); >> for most cases SPARQL Update probably covers the use cases better. >> >> My interpretation is that the deletes of a PATCH can’t really >> reference BNodes in any way, unless the entire graph is removed. >> Updates can, but they’ll always create new BNodes and can’t match >> against existing ones. > > If both client and server are working from the same known base-point, and the PATCH is viewed as operating on the canonical *serialization* of an RDF graph, such as in N-Triple, then it should work fine, just as with any other text file. Certainly, as a text file, limiting the the serialization opportunities to N-Triples or N-Quads (unless a textual transformation from other formats is defined). Also, given a matching ETag, of course. > However, currently there would be a problem in applying that PATCH to RDF that is stored in a SPARQL server, because currently there is no standard way to directly refer to a bnode from a separate SPARQL operation. This is a known problem already with SPARQL, which causes grief when doing followup queries. But if SPARQL servers were enhanced to (optionally) enable subsequent queries or update operations to refer directly to blank nodes by their *original* labels, then both PATCH and followup queries would work on SPARQL servers. (In the case of implicit bnodes generated by Turtle/SPARQL [] or () notation the server would assign an original label.) This seems like a good route to take, though it means adding that feature to SPARQL. I'll send this to the SPARQL list > https://lists.w3.org/Archives/Public/public-sparql-dev/ > to see what others there think. This might only work on SPARQL servers that are capable of “remembering” original identifiers, and can rapidly get out of sync as the dataset changes. Alternatively, some SPARQL servers may use stable internal identifiers that could serve this purpose (still requiring normative normalization), but I suspect that there are some implementations that don’t guarantee such stable identifiers). Gregg > David Booth >
Received on Wednesday, 20 May 2015 23:08:36 UTC