Skip to content

Latest commit

 

History

History
52 lines (32 loc) · 2.14 KB

README.md

File metadata and controls

52 lines (32 loc) · 2.14 KB
Raw

Jena OntoDriver

Allows connecting to Jena-based storage.

Currently supported storage types:

  • In-memory (in-memory)
  • File (file)
  • TDB (tdb)
  • Fuseki (fuseki)

The storage type is configured using the cz.cvut.kbss.ontodriver.jena.storage property.

SDB is not planned, as its development has been discontinued in favor of TDB.

Isolation Strategies

The driver supports two types of transaction isolation strategies:

  • Read committed (read-committed)
  • Snapshot (snapshot)

They are configured using the cz.cvut.kbss.ontodriver.jena.isolation parameter.

Read committed

This strategy uses a shared connector for all read operations. Writing is done into a local change-tracking model. Commit then writes the changes into the central connector.

This strategy is more memory efficient, but it provides lesser isolation between concurrent transactions.

Snapshot

This strategy creates a snapshot of the current storage state when a transaction begins. All subsequent reads/writes are done on this snapshot. In addition, the writes are tracked in a local model. On commit, these changes are propagated into the shared connector.

This puts more demand on the system memory, as the storage may be copied multiple times. However, it provides much higher level of isolation for concurrent access.

Note: This strategy is by default used when inference is configured. This is a must have to allow access to transactional changes in the reasoning process. Therefore, whenever a cz.cvut.jopa.reasonerFactoryClass parameter value is passed in configuration to the driver, it automatically uses snapshot-based transaction isolation strategy, regardless of any direct configuration of the transaction isolation strategy.

Default Graph Treatment

Most storage treat the default graph as a union of all named graphs in the dataset. Jena, on the other hand, uses the default graph as another, IRI-less, graph in the dataset. To get the union-based behavior, use cz.cvut.kbss.ontodriver.jena.default_graph_as_union.

All configuration parameters and values are declared and documented in cz.cvut.kbss.ontodriver.jena.config.JenaOntoDriverProperties.