On 11/07/17 18:08, Daan Reid wrote:
Our use case is to use the Delta to calculate the differences between
graphs for events so we can replay additions and deletions without
storing all the unchanged triples for each graph change event.
You may be interested in
https://afs.github.io/rdf-delta/
which can provide a way to record changes to a dataset.
It is a very different style off approach to the Delta graph. It creates
a log of changes (adds and deletes, and also prefix changes) and ties
into the transaction mechanism.
Andy
Since we've got control over the database and the message converter we
have since made a workaround by canonicalising the DB with some queries,
and from now will use the RDFParser's forced canonical system (thanks
for pointing that out!) on incoming messages to prevent this issue from
affecting us in future.
A Delta wrapper that works by value instead of lexical equality sounds
like it could be a great general solution, because the current
situation's inconsistency is a bit of a gotcha.
For reference to those interested, the inconsistency is located in the
fact that `GraphTripleStoreBase.contains()` checks by values, but
`GraphTripleStoreBase.delete()` defers to `NodeToTriplesMapMem.remove()`
which compares lexically. So in the `Delta.addTriple()`, the base graph
does contain the (semantically equal) triple and hence it is not added
to the additions, but the `deletions.delete()` checks by lexical value
and hence does not delete it.
Regards, and thanks for the help,
Daan Reid
Drugis project -- https://drugis.org
