Hi all,
I've been working on it for a long time outside the main Marmotta tree, but
even though it is still experimental, it is now mature enough to be
included in the development repository of Marmotta: a new triple store
backend implemented in C++ and using LevelDB (http://www.leveldb.org). In
analogy to KiWi, I named it Ostrich - another bird without wings, but one
that runs very fast :)
The Ostrich backend is ultra fast compared to Kiwi (I can import 500k
triples in 7 seconds), but it does not provide the same feature set. In
particular, the following restrictions apply:
- limited transaction support; a transaction is active while only executing
updates, but as soon as you run a query on a connection it will auto-commit
- currently emulated in-memory SPARQL (I started working on direct C++
SPARQL support, but this is not yet available in Java - but performance is
promising, so more to come :) )
- currently emulated LDPath support (I might implement LDPath in C++ if the
emulated performance is not good enough)
- currently no reasoner (it's certainly possible, but a lot of work)
- currently no versioning or snapshotting (might be possible at LevelDB
level, but didn't investigate much)
The new backend consists of a C++ part (server) and a Java part (client).
Client and server communicate with each other using Proto messages and gRPC
(latest snapshot version!). The data model and service definitions are in
the .proto files found in libraries/ostrich/backend.
If you want to try this out, please have a look at the README.md file
located in libraries/ostrich/backend. Besides compiling the C++ code
separately with cmake and make, Marmotta needs to be compiled with
mvn clean install -Postrich -DskipTests
note that the Java code contains tests, but these require a running
backend. So it is for now better to just skip tests when building the Java
part completely.
Bulk imports are best done with the C++ command line client (see
README.md).
Have fun!
Sebastian
P.S. You can now also use the client to try out native SPARQL support:
./client/marmotta_client sparql 'select * where { ?s ?p ?o } limit 10'
The result will be a mostly unreadable text formatted dump of the resulting
proto messages :)
