[JENA-1447] Special case DatasetGraphs

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 3.5.0
• Fix Version/s: Jena 3.6.0
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 10/Dec/17 14:05
• Updated: 09/Apr/18 21:56
• Resolved: 12/Dec/17 10:09

Description

Some specialized datasets:

DatasetGraphOne - a dataset around a single which becomes the default graph. This is the converter from graphs to datasets. A special case is where the graph is GraphView from another dataset. The existing DatasetGraphOne needs upgrading to map dataset transactions back to the original dataset.

DatasetGraphZero - a dataset with no named graph and an always-empty default graph. Convenient to have in place of null pointers.

DatasetGraphSink - a dataset that accepts updated but ignores them and so is always empty.

TransactionalNull - a transactional to reflect the properties of empty datasets.

In support of these:

GraphSink, GraphZero, PrefixMappingSink, PrefixMappingZero and TransactionHandlerNull.

The graphs do not fully comply with the full Graph contract:

• GraphZero throws UnsupportedOperationException, not AddDeniedException/DeleteDeniedException becaue (1) it is in keeping with DatasetGraphZero and (2) AddDeniedException is dynamic - it make be thrown in some situations and not others e.g. permissions.

• GraphSink does not contain triples added.

On naming:

"DatasetGraphZero" might also be "DatasetGraphNull" but /dev/null is a sink.

Issue Links

• links to: GitHub Pull Request #328