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https://issues.apache.org/jira/browse/JENA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16193586#comment-16193586
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Andy Seaborne commented on JENA-1391:
-------------------------------------
Seems like you've answered the question!
There's no connection between the combining operation of the dataset and the
context.
Either empty context or left-to-right merge.
The only general one I can recall is query timeout and that's primarily for
large scale, persistent datasets.
Other than that, there are a few some datasets with specific setting; text
dataset has the index, TDBx has the union setting, both of which do not make
sense automatically for the combined dataset, then the answer is empty, app
needs to set it specially if needed.
Start simple - easier to add later, than remove such a feature.
> Add Convenience Methods to Dataset
> ----------------------------------
>
> Key: JENA-1391
> URL: https://issues.apache.org/jira/browse/JENA-1391
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 3.4.0
> Reporter: Adam Jacobs
> Assignee: A. Soroka
> Priority: Trivial
>
> The Dataset interface could provide several convenience methods similar to
> the Model interface, allowing usability of RDF quads on par with RDF triples.
> Specific examples include,
> # add(Dataset)
> # remove(Dataset)
> # union(Dataset)
> # intersection(Dataset)
> # difference(Dataset)
> # isEmpty()
> Following is a possible implementation of these methods.
> {code:java}
> default Dataset add(Dataset d) {
> this.getDefaultModel().add(d.getDefaultModel());
> d.listNames().forEachRemaining(name ->
> this.getNamedModel(name).add(d.getNamedModel(name)));
> return this;
> }
> default Dataset remove(Dataset d) {
> this.getDefaultModel().remove(d.getDefaultModel());
> d.listNames().forEachRemaining(name ->
> this.getNamedModel(name).remove(d.getNamedModel(name)));
> return this;
> }
> default Dataset union(Dataset d) {
> return DatasetFactory.create().add(this).add(d);
> }
> default Dataset difference(Dataset d) {
> Dataset output = DatasetFactory.create();
>
> output.setDefaultModel(this.getDefaultModel().difference(d.getDefaultModel()));
> this.listNames().forEachRemaining(name -> {
> Model difference =
> this.getNamedModel(name).difference(d.getNamedModel(name));
> if (!difference.isEmpty()) output.addNamedModel(name, difference);
> });
> return output;
> }
> default Dataset intersection(Dataset d) {
> Dataset output = DatasetFactory.create();
>
> output.setDefaultModel(this.getDefaultModel().intersection(d.getDefaultModel()));
> Set<String> names = this.names();
> names.retainAll(d.names());
> names.forEach(name -> {
> Model intersection =
> this.getNamedModel(name).intersection(d.getNamedModel(name));
> if (!intersection.isEmpty()) output.addNamedModel(name,
> intersection);
> });
> return output;
> }
> default Set<String> names() {
> Set<String> names = new HashSet<>();
> this.listNames().forEachRemaining(names::add);
> return names;
> }
> default boolean isEmpty() {
> return this.asDatasetGraph().isEmpty();
> }
> {code}
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