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From "Andy Seaborne (Commented) (JIRA)" <>
Subject [jira] [Commented] (JENA-205) Streaming results for CONSTRUCT queries
Date Mon, 30 Jan 2012 22:19:10 GMT


Andy Seaborne commented on JENA-205:

Personally, I'd go for Iterator<Triple>.  Statements are tied to model; instead, provide
a stream of things that are not tied to models AKA triples (and quads if we extend CONSTRUCT
to have GRAPH like SPARQL Updates).

I also thing that making it distinct should be left out or at most optional.  This is a low
level interface. 

N-triples is easy to stream out, as is Turtle.  RDF/XML is hard enough to warrant not bothering
with for now.  I think that Turtle will quickly displace RDF/XML.

For Fuseki, a trick would be to stream back triples with duplicates - it's still legal RDF
in all serializations to have duplicates.  Then the server is not burdened.

> Streaming results for CONSTRUCT queries
> ---------------------------------------
>                 Key: JENA-205
>                 URL:
>             Project: Jena
>          Issue Type: Improvement
>          Components: ARQ, Fuseki
>            Reporter: Stephen Allen
>            Assignee: Stephen Allen
>            Priority: Minor
> It would be useful to have CONSTRUCT queries that streamed results.  An additional method
on QueryExecution that returned an Iterator<Statement> (or something similar to that
[1]) would provide the necessary access.
> Implementationwise, the application of Bindings to the CONSTRUCT template is already
streaming, we would simply need to perform a distinct operation on the Triples that are created.
 We could use a DistinctDataNet to get semi-streaming with spill-to-disk functionality.
> Additionally, for this to be useful for Fuseki, we also need an RDF/XML serializer that
can operate on an Iterator<Statement> instead of a Model.
> [1] Prefix mappings would probably be nice for serializers that consume this iterator.

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