[jira] [Created] (JENA-1447) Special case DatasetGraphs

["Andy Seaborne (JIRA)" <ji...@apache.org>]

Andy Seaborne created JENA-1447:
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             Summary: Special case DatasetGraphs
                 Key: JENA-1447
                 URL: https://issues.apache.org/jira/browse/JENA-1447
             Project: Apache Jena
          Issue Type: Bug
          Components: ARQ
    Affects Versions: Jena 3.5.0
            Reporter: Andy Seaborne
            Assignee: Andy Seaborne


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}}.

On naming:

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



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