[STANBOL-765] Add support for importing Bnodes to the Jena TDB indexing source

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: entityhub-0.11.0
• Component/s: Entityhub
• Assignee: Rupert Westenthaler
• Reporter: Rupert Westenthaler
• Created: 10/Oct/12 09:34
• Updated: 17/Jul/13 15:14
• Resolved: 14/Dec/12 07:20

Description

The Stanbol Entityhub does (intentional) not support Bnodes (RDF blank nodes) as those are not rereferable. Because of that the Jena TDB indexing source is up to now ignoring Bnodes both for subjects and Objects - basically if a Triple contains any Bnode it is skipped.

While adding support for Bnodes to the Entityhub is not possible it is feasible to allow users to convert Bnode ids to valid URIs by providing a prefix (or base URI) in the configuration of the Jena TDB indexing source.

If this configuration is present Bnodes of the indexed RDF graph will be converted to URIs by using "

{bnode-prefix} {bnodId}

". Users that do use this feature need to be aware that they do change the RDF graph (and do make preciously local resources globally dereferable via the Entityhub RESTful API).

There will be no default value for the bnode prefix. Users will need to explicitly define it (e.g. in the indexing.properties file). If no bnode prefix is configured Bnodes will be skipped (current behavior). This ensures also backward compatibility.

NOTE: This will not fix possible memory problems when importing RDF files that do include BNodes into the Jena TDB indexing source. As Jena needs still to keep an lookup table over all BNodes referenced in the currently imported file.